Green tea supplementation produces better neuroprotective effects than red and black tea in Alzheimer-like rat model

Oral administration of liposome-encapsulated thymol could alleviate the inflammatory parameters in serum and hippocampus in a rat model of Alzheimer's disease

BACKGROUND

Neuroinflammation is closely related to Alzheimer's Disease (AD) pathology, hence supplements with anti-inflammatory property could help attenuate the progression of AD. This study was conducted to evaluate the potential anti-inflammatory effects of liposome encapsulated thymol (LET), administered orally, in prevention of Alzheimer in a rat model by anti-inflammatory mechanisms.

METHODS

The rats were grouped into six groups (n = 10 animals per group), including Control healthy (Con), Alzheimer's disease (AD) model, AD model treated with free thymol in 40 and 80 mg/kg body weight (TH40 and TH80), AD model treated with LET in 40 and 80 mg/kg of body weight (LET40 and LET80). The behavioral response of step through latency (Passive Avoidance Test), concentrations of interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) and cyclooxygenase-2 (COX-2) and brain-derived neurotrophic factor (BDNF) were assessed in serum and hippocampus.

RESULTS

The results showed that significant increase in concentrations of IL-1β (P = 0.001), IL-6 (P = 0.001), TNF-α (P = 0.001) and COX-2 (P = 0.001) in AD group compared with healthy control rats. AD induction significantly reduced step through latency and revealed deficits in passive avoidance performance. The results also showed the treatment with free thymol especially in higher concentrations and also LTE could decrease serum concentrations of IL-1β (P < 0.05), IL-6 (P < 0.05), TNF-α (P < 0.05), and COX-2 (P < 0.05) and increase BDNF (P < 0.05) compared with control Alzheimer rats in hippocampus and serum. There were also significant correlations between serum and hippocampus concentrations of IL-1β (r2 = 0.369, P = 0.001), IL-6 (r2 = 0.386, P = 0.001), TNF-α (r2 = 0.412, P = 0.001), and COX-2 (r2 = 0.357, P = 0.001). It means a closed and positive relation between serum and hippocampus concentrations of IL-1β, IL-6, TNF-α, and COX-2.

CONCLUSIONS

LET demonstrates its ability to attenuate neuroinflammatory reaction in AD model through suppression of IL-1β, IL-6, and TNF-α and COX-2 indicators. Hence, it can ameliorate AD pathogenesis by declining inflammatory reaction.

Unraveling the Bioactive Potential of Camellia japonica Edible Flowers: Profiling Antioxidant Substances and In Vitro Bioactivity Assessment

In recent years, the search for novel natural-based ingredients by food and related industries has sparked extensive research aimed at discovering new sources of functional molecules. Camellia japonica, traditionally known as an ornamental plant, has gained attention due to its diverse array of bioactive compounds with potential industrial applications. Although C. japonica flowers are edible, their phytochemical profile has not been thoroughly investigated. In this study, a phenolic profile screening through an HPLC-ESI-QQQ-MS/MS approach was applied to C. japonica flower extracts, revealing a total of 36 compounds, including anthocyanins, curcuminoids, dihydrochalcones, dihydroflavonols, flavonols, flavones, hydroxybenzoic acids, hydroxycinnamic acids, isoflavonoids, stilbenes, and tyrosols. Following extract profiling, their bioactivity was assessed by means of in vitro antioxidant, antimicrobial, cytotoxic, and neuroprotective activities. The results showed a multifaceted high correlation of phenolic compounds with all the tested bioactivities according to Pearson's correlation analysis, unraveling the potential of C. japonica flowers as promising sources of nutraceuticals. Overall, these findings provide insight into the valorization of C. japonica flowers from different unexplored cultivars thus diversifying their industrial outcome.

Addressing neurodegeneration in glaucoma: Mechanisms, challenges, and treatments

Glaucoma is the leading cause of irreversible blindness globally. The disease causes vision loss due to neurodegeneration of the retinal ganglion cell (RGC) projection to the brain through the optic nerve. Glaucoma is associated with sensitivity to intraocular pressure (IOP). Thus, mainstay treatments seek to manage IOP, though many patients continue to lose vision. To address neurodegeneration directly, numerous preclinical studies seek to develop protective or reparative therapies that act independently of IOP. These include growth factors, compounds targeting metabolism, anti-inflammatory and antioxidant agents, and neuromodulators. Despite success in experimental models, many of these approaches fail to translate into clinical benefits. Several factors contribute to this challenge. Firstly, the anatomic structure of the optic nerve head differs between rodents, nonhuman primates, and humans. Additionally, animal models do not replicate the complex glaucoma pathophysiology in humans. Therefore, to enhance the success of translating these findings, we propose two approaches. First, thorough evaluation of experimental targets in multiple animal models, including nonhuman primates, should precede clinical trials. Second, we advocate for combination therapy, which involves using multiple agents simultaneously, especially in the early and potentially reversible stages of the disease. These strategies aim to increase the chances of successful neuroprotective treatment for glaucoma.

Red Cabbage Anthocyanins Attenuate Cognitive Impairment By Attenuating Neuroinflammation and Regulating Gut Microbiota in Aging Mice

Red cabbage anthocyanins may provide health benefits that may be associated with antiaging. The protection of red cabbage anthocyanin-rich extract (ARE) and cyanidin-3-diglucoside-5-glucoside-rich extract (CY3D5G) against age-related cognitive dysfunction was investigated in normal aging mice (male C57BL/6J, 12 months old) administered orally for 12 weeks. Behavioral tests showed that ARE and CY3D5G significantly decreased cognitive impairment (p < 0.05) and had no effect on motor disorder. ARE and CY3D5G increased superoxide dismutase activity by 29.18 and 23.09% and decreased malondialdehyde by 15.74 and 10.05%, respectively, compared to the control. Histological staining showed that ARE and CY3D5G treatment reduced hippocampal neuronal damage and brain-derived neurotrophic factor degeneration. ARE and CY3D5G significantly reduced IL-1β and IL-6 levels in serum and brain (p < 0.05) by promoting the MAPK signaling pathway while enriching the abundance of butyrate-producing bacteria and altering the functional profile of the microbial community. In conclusion, ARE and CY3D5G may attenuate age-related cognitive dysfunction by reducing neuroinflammation and regulating the gut-brain axis.

6-Aminoflavone Activates Nrf2 to Inhibit the Phospho-JNK/TNF-α Signaling Pathway to Reduce Amyloid Burden in an Aging Mouse Model

In the current study, we examined the antioxidant activity and anti-amyloidogenic potential of 6-aminoflavone in an adult mice model of d-galactose-induced aging. Male albino eight-week-old mice were assigned into four groups: 1. the control group (saline-treated), 2. d-galactose-treated mice (100 mg/kg/day, intravenously) for eight weeks, 3. d-galactose-treated mice (100 mg/kg/day, intravenously for eight weeks) and 6-AF-treated mice (30 mg/kg/day, intravenously for the final four weeks), and 4. 6-AF-treated mice (30 mg/kg/day i.p. for four weeks). We conducted many assays for antioxidant enzymes, including lipid peroxidation, catalase, glutathione (GSH), peroxidase (POD), and sulfoxide dismutase (SOD) (LPO). Western blotting was used to assess protein expression while the Morris water maze (MWM) and Y-maze (YM) were used to study behavior. The findings show that 6-AF greatly improved neuronal synapse and memory impairment brought on by d-galactose and it significantly inhibited BACE1 to reduce the amyloidogenic pathway of A (both amyloid β production and aggregation) by upregulating Nrf2 proteins (validated through molecular docking studies) and suppressing phosphorylated JNK and TNF-α proteins in adult albino mice's brain homogenates. These findings suggest that 6-AF, through the Nrf2/p-JNK/TNF-α signaling pathway, can diminish the oxidative stress caused by d-galactose, as well as the amyloidogenic route of A formation and memory impairment.

Tea intake or consumption and the risk of dementia: a meta-analysis of prospective cohort studies

Purpose

Dementia affects as many as 130 million people, which presents a significant and growing medical burden globally. This meta-analysis aims to assess whether tea intake, tea consumption can reduce the risk of dementia, Alzheimer's disease (AD) and Vascular dementia (VD).

Patients and methods

Cochrane Library, PubMed and Embase were searched for cohort studies from inception to November 1, 2022. The Newcastle Ottawa Quality Assessment Scale (NOS) was applied to evaluate the risk of bias of the included studies. We extracted the data as the relative risks (RRs) for the outcome of the interest, and conducted the meta-analysis utilizing the random effect model due to the certain heterogeneity. Sensitivity analysis were performed by moving one study at a time, Subgroup-analysis was carried out according to different ages and dementia types. And the funnel plots based on Egger's and Begger's regression tests were used to evaluate publication bias. All statistical analyses were performed using Stata statistical software version 14.0 and R studio version 4.2.0.

Results

Seven prospective cohort studies covering 410,951 individuals, which were published from 2009 and 2022 were included in this meta-analysis. The methodological quality of these studies was relatively with five out of seven being of high quality and the remaining being of moderate. The pooling analysis shows that the relationship between tea intake or consumption is associated with a reduced risk of all-cause dementia (RR = 0.71, 95% CI [0.57-0.88], I² = 79.0%, p < 0.01). Further, the subgroup-analysis revealed that tea intake or consumption is associated with a reduced risk of AD (RR = 0.88, 95% CI [0.79-0.99], I² = 52.6%, p = 0.024) and VD (RR = 0.75, 95% CI [0.66-0.85], I = 0.00%, p < 0.001). Lastly, tea intake or consumption could reduce the risk of all-cause dementia to a greater degree among populations with less physical activity, older age, APOE carriers, and smokers.

Conclusion

Our meta-analysis demonstrated that tea (green tea or black tea) intake or consumption is associated with a significant reduction in the risk of dementia, AD or VD. These findings provide evidence that tea intake or consumption should be recognized as an independent protective factor against the onset of dementia, AD or VD.

Biosynthesized Selenium Nanoparticles Using Epigallocatechin Gallate Protect against Pentylenetetrazole-Induced Acute Epileptic Seizures in Mice via Antioxidative, Anti-Inflammatory, and Anti-Apoptotic Activities

Several negative outcomes are associated with current anti-epileptic medications. Epigallocatechin gallate (EGCG) is a plant-derived compound called catechin and has many medicinal activities, such as anti-inflammatory and antioxidant activities. Biosynthesized selenium nanoparticles are also showing their neuroprotective effect. The anti-epileptic effect of EGCG, alone or with SeNPs, is still debated. Here, we aimed to investigate the potential anti-seizure effect of biosynthesized SeNPs using EGCG (EGCG-SeNPs) against epileptic seizures and hippocampal damage, which is enhanced by pentylenetetrazole (PTZ) injection in mice. Mice were grouped as follows: control; PTZ-exposed group (epileptic model); EGCG + PTZ-treated group; sodium selenite (Na₂SeO₃) + PTZ-treated group; EGCG-SeNPs + PTZ-treated group; and valproic acid (VPA) + PTZ-treated group. EGCG-SeNPs administration showed anti-epileptic activity by increasing the latency time and reducing the seizure duration following the PTZ injection. Additionally, EGCG-SeNPs counteracted the PTZ-induced changes in oxidants and antioxidants. Moreover, EGCG-SeNPs inhibited the inflammatory response by suppressing the release of pro-inflammatory cytokines and decreasing the immunoreactivity of the glial fibrillary acidic protein and mRNA expression of glutamate receptor subunit zeta-1 (NMDAR; Grin1), showing their inhibitory effect on epilepsy-associated inflammation. Moreover, EGCG-SeNPs reduced PTZ-induced neuronal apoptosis, as indicated by a reduction in the levels of pro-apoptotic proteins and an elevation of the anti-apoptotic protein. Moreover, EGCG-SeNPs administration significantly modulated the PTZ-induced changes in monoamine levels and acetylcholinesterase activity in the hippocampal tissue. The obtained findings suggest the anti-seizure activity of EGCG-SeNPs via their antioxidant, anti-inflammatory, and anti-apoptotic effects, along with their neuromodulatory effect.

Molecular Aspects of a Diet as a New Pathway in the Prevention and Treatment of Alzheimer's Disease

Alzheimer's disease is the most common cause of dementia in the world. Lack of an established pathology makes it difficult to develop suitable approaches and treatment for the disease. Besides known hallmarks, including amyloid β peptides cumulating in plaques and hyperphosphorylated tau forming NFTs, inflammation also plays an important role, with known connections to the diet. In AD, adhering to reasonable nutrition according to age-related principles is recommended. The diet should be high in neuroprotective foods, such as polyunsaturated fatty acids, antioxidants, and B vitamins. In addition, foods capable of rising BDNF should be considered because of the known profitable results of this molecule in AD. Adhering to beneficial diets might result in improvements in memory, cognition, and biomarkers and might even reduce the risk of developing AD. In this review, we discuss the effects of various diets, foods, and nutrients on brain health and possible connections to Alzheimer's disease.

Minocycline effects on memory and learning impairment in the beta-amyloid-induced Alzheimer's disease model in male rats using behavioral, biochemical, and histological methods

Alzheimer's disease (AD), as an advanced neurodegenerative disease, is characterized by the everlasting impairment of memory, which is determined by hyperphosphorylation of intracellular Tau protein and accumulation of beta-amyloid (Aβ) in the extracellular space. Minocycline is an antioxidant with neuroprotective effects that can freely cross the blood-brain barrier (BBB). This study investigated the effect of minocycline on the changes in learning and memory functions, activities of blood serum antioxidant enzymes, neuronal loss, and the number of Aβ plaques after AD induced by Aβ in male rats. Healthy adult male Wistar rats (200-220g) were divided randomly into 11 groups (n = 10). The rats received minocycline (50 and 100 mg/kg/day; per os (P.O.)) before, after, and before/after AD induction for 30 days. At the end of the treatment course, behavioral performance was measured by standardized behavioral paradigms. Subsequently, brain samples and blood serum were collected for histological and biochemical analysis. The results indicated that Aβ injection impaired learning and memory performances in the Morris water maze test, reduced exploratory/locomotor activities in the open field test, and enhanced anxiety-like behavior in the elevated plus maze. The behavioral deficits were accompanied by hippocampal oxidative stress (decreased glutathione (GSH) peroxidase enzyme activity and increased malondialdehyde (MDA) levels in the brain (hippocampus) tissue), increased number of Aβ plaques, and neuronal loss in the hippocampus evidenced by Thioflavin S and H&E staining, respectively. Minocycline improved anxiety-like behavior, recovered Aβ-induced learning and memory deficits, increased GSH and decreased MDA levels, and prevented neuronal loss and the accumulation of Aβ plaques. Our results demonstrated that minocycline has neuroprotective effects and can reduce memory dysfunction, which are due to its antioxidant and anti-apoptotic effects.

Evaluation of the effect of green tea and its constituents on embryo development in a zebrafish model

As one of the most popular beverages, green tea has attracted much interest for its beneficial effects on human health. However, the toxicity of green tea and its underlying mechanism are still poorly understood. Here, we evaluated the effect of green tea and its constituents on development by exposing zebrafish embryos to them. Morphologic results demonstrated that 0.1% and 0.2% green tea increased mortality, delayed epiboly of gastrulation, and shortened body length. Green tea altered the expression pattern of dlx3, cstlb, myod, and papc and decreased the expression levels of wnt5 and wnt11, suggesting that green tea disturbed convergence and extension movement through the downregulation of wnt5 and wnt11. The increased expression of the dorsal gene chordin and reduced expression of wnt8 and its target genes vox and vent in embryos exposed to 0.1% and 0.2% green tea indicated that green tea could affect dorsoventral differentiation by inhibiting the wnt8 signaling pathway. Additionally, green tea could inhibit epiboly progression by disrupting F-actin organization or removing F-actin in vegetal yolks during gastrulation. However, no malformation was caused by exposure to the five catechins and gallic acid individually. The mixture of constituents showed a similar effect to green tea solution on the embryos, such as smaller eyes and head, shorter body length, and slower heart rate, which indicated that the effect of green tea solution on embryo development was mainly due to the comprehensive effect of multiple components in the green tea solution.

Protective effects of Forsythiae fructus and Cassiae semen water extract against memory deficits through the gut-microbiome-brain axis in an Alzheimer's disease model

CONTEXT

Fruits of Forsythia suspensa Vahl (Oleaceae) and seeds of Cassia obtusifolia Linne (Caesalpinaceae) have been used to treat inflammation in Asia.

OBJECTIVE

We examined the alleviation of memory function in Alzheimer's disease (AD) rats fed Forsythiae Fructus (FF) and Cassiae Semen water extracts (CS) and investigated the mechanisms responsible for the effects.

MATERIALS AND METHODS

Thirty Sprague-Dawley male rats had hippocampal infusions of amyloid-β_(25-35) (AD rats; memory deficit), and ten rats were infused with amyloid-β_(35-25) (non-AD rats; no memory deficit). For eight weeks, all rats freely consumed high-fat diets (43% lard) incorporated with 200 mg/kg body weight assigned aqueous herbal extracts: AD-FF, AD-CS, or without extracts AD-CON (control), non-AD (normal-control).

RESULTS

Memory impairment was prevented in the AD-FF (0.54 ± 0.06-fold) and the AD-CS rats (0.33 ± 0.04-fold) compared to the AD-CON by inhibiting amyloid-β deposition to the levels less than one-fourth of the AD-CON group. The hippocampal pAkt→pGSK-3β→pFOXO1 pathway was attenuated by approximately 3.25-fold in the AD-CON, while AD-FF prevented the attenuation better than AD-CS. The relative intensity of hippocampal tau protein based on β-actin was suppressed with AD-FF (0.68 ± 0.09) and AD-CS (0.96 ± 0.81), compared to AD-CON (1.19 ± 0.13). AD decreased the abundance of Bacteroidales by 34.2% and Lactobacillales by 23.8% and increased Clostridiales by 181% while the AD-FF, but not the AD-CS, normalised the gut microbiota changes to be similar to the non-AD.

DISCUSSION AND CONCLUSIONS

FF improved memory deficits better than CS in an AD-induced rat model. The potential neuroprotective benefits of FF against AD may be applicable to human AD therapy with additional clinical research.

Immune-biochemical response and immune gene expression profiling of Labeo rohita fingerlings fed with ethanolic tea leaf extracts and its survivability against Aeromonas hydrophila infection

The present study was conducted to evaluate the immunostimulatory effect of tea leaf extract (Camellia sinensis) on Labeo rohita and its resistance against Aeromonas hydrophila infection. The ethanolic extract of green tea (GTEE) was found to be the most potent as compared to other solvent extract which was used for further study. It was used to evaluate immune-biochemical response of L. rohita fingerlings, fed with tea leaf extract (control- 0.0%, 0.2% (T1), 0.4% (T2), 0.8% (T3) and 1% (T4) of GTEE kg^-1 feed). Different biochemical parameters like glucose, ALP, GPT, GOT, and immunological parameters like lysozyme activity, NBT, anti-protease activity, myeloperoxidase activity, plasma protein, and immune relevant genes (IL-10, C3, Lysozyme G type and iNOS) expressions were carried out. The immunological parameters such as lysozyme activity, NBT and myeloperoxidase activity showed significantly high value once fed with GTEE incorporated diets. Significant up-regulation of immune genes indicated the enhancement of immune response at molecular level. The biochemical parameters were found to be significantly decreasing, indicating that the extract had hepato-protective effect and can help to overcome stress. The fish, fed with GTEE incorporated diets, showed resistance against A. hydrophila when compared with the control group. 0.2% GTEE showed the highest post-challenged survival (76.67%). From the present study, it is concluded that GTEE @ 0.2% can be used as potent immunostimulant as a sustainable alternative prophylactic and therapeutic agent in aquaculture.

Pharmacological effects and therapeutic potential of natural compounds in neuropsychiatric disorders: An update

Neuropsychiatric diseases are a group of disorders that cause significant morbidity and disability. The symptoms of psychiatric disorders include anxiety, depression, eating disorders, autism spectrum disorders (ASD), attention-deficit/hyperactivity disorder, and conduct disorder. Various medicinal plants are frequently used as therapeutics in traditional medicine in different parts of the world. Nowadays, using medicinal plants as an alternative medication has been considered due to their biological safety. Despite the wide range of medications, many patients are unable to tolerate the side effects and eventually lose their response. By considering the therapeutic advantages of medicinal plants in the case of side effects, patients may prefer to use them instead of chemical drugs. Today, the use of medicinal plants in traditional medicine is diverse and increasing, and these plants are a precious heritage for humanity. Investigation about traditional medicine continues, and several studies have indicated the basic pharmacology and clinical efficacy of herbal medicine. In this article, we discuss five of the most important and common psychiatric illnesses investigated in various studies along with conventional therapies and their pharmacological therapies. For this comprehensive review, data were obtained from electronic databases such as MedLine/PubMed, Science Direct, Web of Science, EMBASE, DynaMed Plus, ScienceDirect, and TRIP database. Preclinical pharmacology studies have confirmed that some bioactive compounds may have beneficial therapeutic effects in some common psychiatric disorders. The mechanisms of action of the analyzed biocompounds are presented in detail. The bioactive compounds analyzed in this review are promising phytochemicals for adjuvant and complementary drug candidates in the pharmacotherapy of neuropsychiatric diseases. Although comparative studies have been carefully reviewed in the preclinical pharmacology field, no clinical studies have been found to confirm the efficacy of herbal medicines compared to FDA-approved medicines for the treatment of mental disorders. Therefore, future clinical studies are needed to accelerate the potential use of natural compounds in the management of these diseases.

Green tea improves cognitive function through reducing AD-pathology and improving anti-oxidative stress capacity in Chinese middle-aged and elderly people

Background: Numerous benefits of green tea have been reported. However, the effects of green tea on cognitive function remain disputable and the mechanism is still unclear.

Objective: To investigate the relationship of green tea consumption with cognitive function and related blood biomarkers among Chinese middle-aged and elderly people.

Methods: A total of 264 participants aged 50–70 years old were enrolled from Zhongnan Hospital of Wuhan University. They were interviewed about green tea consumption patterns and underwent neuropsychological tests covering five main cognitive domains to assess cognition including Montreal Cognitive Assessment (MoCA) and the other 10 scales. Then we detected serum oxidative stress biomarkers including Superoxide Dismutase (SOD), Malondialdehyde (MDA), Glutathione Peroxidase (GPx), Glutathione Reductase (GR), and Alzheimer’s disease (AD) markers including β-amyloid (Aβ)₄₀, Aβ₄₂, and phosphorylated tau-181 (pTau₁₈₁).

Results: In the tea-consuming group, the MoCA scores (P = 0.000), Hopkins Verbal Learning Test (HVLT) immediate recall (P = 0.012) and delayed recall (P = 0.013) were significantly higher while Trail Making Test-B (P = 0.005) and Victoria Stroop test interference (P = 0.000) were lower. In terms of oxidative stress markers, the tea-consuming group had lower serum MDA levels (P = 0.002) and higher serum SOD (P = 0.005) and GPx (P = 0.007) levels. In terms of AD markers, serum pTau₁₈₁ (P < 0.000), Aβ₄₂ (P = 0.019) and total Aβ levels (P = 0.034) but not serum Aβ₄₀ levels, were lower in the tea-consuming group. In the logistic regression analysis, there was a significant negative correlation between green tea consumption and cognitive impairment (OR = 0.26, 95 % CI 0.13 0.52 for high group).

Conclusion: Regular green tea consumption is associated with better cognitive function among Chinese middle-aged and elderly people, mainly reflected in memory and executive function. It may achieve protective effects by reducing AD-related pathology and improving anti-oxidative stress capacity and higher levels of tea consumption have a stronger protective effect.

Potential natural products for the management of autism spectrum disorder

Autism in a broader sense is a neurodevelopmental disorder, which frequently occurs during early childhood and can last for a lifetime. This condition is primarily defined by difficulties with social engagement, with individuals displaying repetitive and stereotyped behaviors. Numerous neuroanatomical investigations on autistic children have revealed that their brains grow atypically, resulting in atypical neurogenesis, neuronal migration, maturation, differentiation, and degeneration. Special education programs, speech therapy, and occupational therapy have all been used to address autism-related behavioral problems. While widely prescribed antidepressant drugs, antipsychotics, anticonvulsants, and stimulants have demonstrated response in autistic individuals. However, these medications do not fully reverse the core symptoms associated with autism spectrum disorder (ASD). The adverse reactions of ASD medicines and an increased risk of developing various other problems, such as obesity, dyslipidemia, diabetes mellitus, and thyroid disorders, prompted the researchers to investigate herbal medicines for the treatment of autistic individuals. Clinical trials are now being done to establish the efficacy of alternative techniques based on natural substances and to understand better the context in which they may be used to treat autism. This review of literature will look at crucial natural compounds derived from animals and plants that have shown promise as safe and effective autism treatment strategies.

Green Tea (Camellia sinensis): A Review of Its Phytochemistry, Pharmacology, and Toxicology

Objectives Green tea (Camellia sinensis) is a kind of unfermented tea that retains the natural substance in fresh leaves to a great extent. It is regarded as the second most popular drink in the world besides water. In this paper, the phytochemistry, pharmacology, and toxicology of green tea are reviewed systematically and comprehensively. Key findings Green tea has been demonstrated to be good for human health. Nowadays, multiple pharmacologically active components have been isolated and identified from green tea, including tea polyphenols, alkaloids, amino acids, polysaccharides, and volatile components. Recent studies have demonstrated that green tea shows versatile pharmacological activities, such as antioxidant, anticancer, hypoglycemic, antibacterial, antiviral, and neuroprotective. Studies on the toxic effects of green tea extract and its main ingredients have also raised concerns including hepatotoxicity and DNA damage. Summary Green tea can be used to assist the treatment of diabetes, Alzheimer’s disease, oral cancer, and dermatitis. Consequently, green tea has shown promising practical prospects in health care and disease prevention.

Habitual tea consumption and postoperative delirium after total hip/knee arthroplasty in elderly patients: The PNDABLE study

PURPOSE

To clarify the effects of habitual tea consumption on postoperative delirium (POD) in elderly patients undergoing total hip/knee arthroplasty.

PATIENTS AND METHODS

A prospective cohort study was carried out at Qingdao Municipal Hospital Affiliated to Qingdao University between June 2020 and June 2021. A total of 332 patients aged 65-85 years undergoing total hip/knee arthroplasty under combined spinal and epidural anesthesia were enrolled from the Perioperative Neurocognitive Disorder and Biomarker Lifestyle (PNDABLE) study in the final analysis, consisting of 168 patients with habitual tea consumption and 164 patients with infrequent tea consumption. The primary endpoint was the effects of habitual tea consumption on POD and the incidence of POD, which was assessed by the Confusion Assessment Method (CAM) twice daily during the first 7 postoperative days, and POD severity was measured by the Memorial Delirium Assessment Scale (MDAS). The secondary endpoints were the concentrations of caffeine and tea polyphenols in plasma and cerebrospinal fluid (CSF), which were detected by the enzyme-linked immunosorbent assay.

RESULTS

POD occurred in 61 of 332 patients (18.37%), among whom 19 had habitual tea consumption (5.72%) and 42 had infrequent tea consumption (12.65%). Habitual tea consumption (odds ratio [OR] = 0.370, 95% confidence interval [CI]: 0.205-0.670, P = .001) was significantly associated with POD in the logistic analysis, and then after adjusting for age and American Society of Anesthesiologists (ASA) physical status (OR = 0.353, 95% CI: 0.190-0.655, P = .001). Furthermore, caffeine in T₀ plasma (OR = 0.834, 95% CI: 0.752-0.924, P = .001), T₁ plasma (OR = 0.818, 95% CI: 0.738-0.908, P < .001), and CSF (OR = 0.899, 95% CI: 0.820-0.984, P = .022) and tea polyphenols in T₀ plasma (OR = 0.541, 95% CI: 0.416-0.704, P < .001), T₁ plasma (OR = 0.477, 95% CI: 0.359-0.633, P < .001), and CSF (OR = 0.526, 95% CI: 0.397-0.696, P < .001) were associated with POD after adjusting for age and ASA physical status.

CONCLUSION

Habitual tea consumption may be associated with a lower incidence of POD in elderly patients.

Metabolomics Study Suggests the Mechanism of Different Types of Tieguanyin (Oolong) Tea in Alleviating Alzheimer’s Disease in APP/PS1 Transgenic Mice

Previously, we found that three types of Tieguanyin tea (Tgy-Q, Tgy-N and Tgy-C) extracts could alleviate Alzheimer’s disease (AD) in a mouse model among which Tgy-C was more effective. In this study, APP/PS1 transgenic mice were used to investigate the metabolomic changes in the feces of mice treated with Tieguanyin tea extracts. Results showed that the profile of fecal metabolites was obviously changed in AD mice. Metabolomics analysis found the effects of Tgy-C, especially its decreasing effect on the fecal metabolites in AD mice—132 of the 155 differential metabolites were decreased. KEGG enrichment revealed that differential metabolites could participate in functional pathways including protein digestion and absorption, biosynthesis of amino acids and ABC transporters. Further comparisons of the metabolites between groups showed that although Tgy-N and Tgy-Q exerted a decreasing effect on the fecal metabolites, Tgy-C was more effective. Moreover, correlation analysis found that the levels of the fecal metabolites were highly correlated with the contents of functional components in tea extracts. Finally, 16S rDNA sequencing presented that Tieguanyin extracts modified the gut microbiota by targeting diverse bacteria. In this study, we investigated the differences of three types of Tieguanyin tea extracts on the fecal metabolites as well as the bacterial community of the gut microbiota in AD mice. The identified differential metabolites and the changed intestinal bacteria might provide potential diagnostic biomarkers for the occurrence and progression of AD.

Tea combats circadian rhythm disorder syndrome via the gut-liver-brain axis: potential mechanisms speculated

Circadian rhythm is an intrinsic mechanism developed by organisms to adapt to external environmental signals. Nowadays, owing to the job and after-work entertainment, staying up late - Circadian rhythm disorders (CRD) are common. CRD is linked to the development of fatty liver, type 2 diabetes, and chronic gastroenteritis, which affecting the body's metabolic and inflammatory responses via multi-organ crosstalk (gut-liver-brain axis, etc.). However, studies on the mechanisms of multi-organ interactions by CRD are still weak. Current studies on therapeutic agents for CRD remain inadequate, and phytochemicals have been shown to alleviate CRD-induced syndromes that may be used for CRD-therapy in the future. Tea, a popular phytochemical-rich beverage, reduces glucolipid metabolism and inflammation. But it is immature and unclear in the mechanisms of alleviation of CRD-mediated syndrome. Here, we have analyzed the threat of CRD to hosts and their offspring' health from the perspective of the "gut-liver-brain" axis. The potential mechanisms of tea in alleviating CRD were further explored. It might be by interfering with bile acid metabolism, tryptophan metabolism, and G protein-coupled receptors, with FXR, AHR, and GPCR as potential targets. We hope to provide new perspectives on the role of tea in the prevention and mitigation of CRD.HighlightsThe review highlights the health challenges of CRD via the gut-liver-brain axis.CRD research should focus on the health effects on healthy models and its offspring.Tea may prevent CRD by regulating bile acid, tryptophan, and GPCR.Potential targets for tea prevention and mitigation of CRD include FXR, AHR and GPCR.A comprehensive assessment mechanism for tea in improving CRD should be established.

Protective Effects of Green Tea Supplementation against Lead-Induced Neurotoxicity in Mice

The use of natural products as therapeutic agents is rapidly growing recently. In the current study, we investigated the protective effects of green tea supplementation on lead-induced toxicity in mice. Forty albino mice were divided into four groups as follows: A: control group; B: green tea receiving group; C: lead-intoxicated group; and D: lead-intoxicated group supplemented with green tea. At the end of the experiment, the animals were tested for neurobehavioral and biochemical alterations. Green tea was analyzed through Gas Chromatography–Mass Spectrometry (GC/MS) analysis. We found that supplementation with green tea ameliorated the lead-associated increase in body weight and blood glucose. Green tea supplementation also changed the blood picture that was affected due to lead toxicity and ameliorated lead-induced dyslipidemia. The group of mice that were supplemented with green tea has shown positive alterations in locomotory, anxiety, memory, and learning behaviors. The GC/MS analysis revealed many active ingredients among which the two most abundant were caffeine and 1,2-benzenedicarboxylic acid, mono(2-ethylhexyl) ester. We concluded that green tea supplementation has several positive effects on the lead-induced neurotoxicity in mice and that these effects may be attributed to its main two active ingredients.

Tieguanyin Oolong Tea Extracts Alleviate Behavioral Abnormalities by Modulating Neuroinflammation in APP/PS1 Mouse Model of Alzheimer's Disease

Alzheimer’s disease (AD) is a common neurodegenerative disease; tea components have important neuroprotective effects. This article explores the effects and mechanisms of Qingxiang Tiguanyin (Tgy-Q), Nongxiang Tieguanyin (Tgy-N), and Chenxiang Tieguanyin (Tgy-C) extracts on APP/PS1 AD model mice. Morris water maze and new object recognition experiments show that Tieguanyin extracts can effectively enhance the cognitive ability of APP/PS1 mice. H&E staining, Nissl staining, and immunohistochemical staining show that Tieguanyin extracts make nerve cell boundaries and nucleoli become clearer, relieve nucleus pyknosis, and effectively reduce Aβ1-40 and Aβ1-42 in the hippocampus and cortex. They also restore the morphology of microglia and astrocytes. In addition, Tieguanyin extracts can balance the oxidative stress level in the brain of APP/PS1 mice by improving the antioxidant capacity. Western blot results show that Tieguanyin extracts can reduce the expression of NF-κB p65, TNF-α, IL-1β, IL-6, COX-2, and iNOS in mouse brain, which demonstrates that Tieguanyin extracts improves cognitive ability by alleviating inflammation. This article demonstrates for the first time that Tieguanyin extracts can inhibit the excessive activation of the NF-κB p65 signaling pathway and improve the antioxidant capacity in the cerebral cortex and hippocampus, to improve the cognitive ability of APP/PS1 mice. Our results shed light into the beneficial of Tieguanyin tea extracts on preventing and alleviating AD diseases.

The effects of green tea on cognitive impairments in the rat model of Alzheimer's disease: protection against inflammatory and oxidative damage

INTRODUCTION

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by a decrement in the number of synapses, an increment in the production of oxygen free radicals and inflammatory cytokines. Green tea (GT) plays a defensive performance in different neurodegenerative conditions, such as cognition deficit. This study investigated the neuroprotective effect of green tea (GT) on cognitive disorder, inflammation, and oxidative stress in the streptozotocin (STZ)- induced AD model.

MATERIALS AND METHODS

The rats were divided into four groups: (1) Control, (2) GT, (3) Alz, and (4) GT + Alz. AD was induced by the injection of STZ (3 mg/kg, bilaterally, ICV). Morris water maze and passive avoidance tests were done to evaluate the memory and learning of rats. Biochemical parameters were measured with specialized ELISA kits.

RESULTS

Briefly, data analysis revealed that GT administration for 21 days improved memory impairment induced by the injection of STZ. Pretreatment with GT enhanced time spent in the goal quarter and reduced latency time and path length. Furthermore, pretreatment with GT prevented the increment of malondialdehyde (MDA) concentration in STZ-treated rats. As a pro-inflammatory cytokine, tumor necrosis factor- α (TNF-α) concentration was suppressed with the GT pretreatment. Total antioxidant capacity was increased after GT administration in rats treated compared with AD rats.

CONCLUSIONS

GT pretreatment attenuated STZ-induced learning and memory impairment through the suppression of TNF-α and MDA concentrations. The beneficial effects of GT on memory could be attributed to its protective effects on oxidative defenses.

Green Tea Polyphenol Epigallocatechin-Gallate in Amyloid Aggregation and Neurodegenerative Diseases

The accumulation of protein aggregates in human tissues is a hallmark of more than 40 diseases called amyloidoses. In seven of these disorders, the aggregation is associated with neurodegenerative processes in the central nervous system such as Alzheimer’s disease (AD), Parkinson’s disease (PD), and Huntington’s disease (HD). The aggregation occurs when certain soluble proteins lose their physiological function and become toxic amyloid species. The amyloid assembly consists of protein filament interactions, which can form fibrillar structures rich in β-sheets. Despite the frequent incidence of these diseases among the elderly, the available treatments are limited and at best palliative, and new therapeutic approaches are needed. Among the many natural compounds that have been evaluated for their ability to prevent or delay the amyloidogenic process is epigallocatechin-3-gallate (EGCG), an abundant and potent polyphenolic molecule present in green tea that has extensive biological activity. There is evidence for EGCG’s ability to inhibit the aggregation of α-synuclein, amyloid-β, and huntingtin proteins, respectively associated with PD, AD, and HD. It prevents fibrillogenesis (in vitro and in vivo), reduces amyloid cytotoxicity, and remodels fibrils to form non-toxic amorphous species that lack seed propagation. Although it is an antioxidant, EGCG in an oxidized state can promote fibrils’ remodeling through formation of Schiff bases and crosslinking the fibrils. Moreover, microparticles to drug delivery were synthesized from oxidized EGCG and loaded with a second anti-amyloidogenic molecule, obtaining a synergistic therapeutic effect. Here, we describe several pre-clinical and clinical studies involving EGCG and neurodegenerative diseases and their related mechanisms.

Associations of Green Tea Consumption and Cerebrospinal Fluid Biomarkers of Alzheimer's Disease Pathology in Cognitively Intact Older Adults: The CABLE Study

BACKGROUND

Green tea has been widely recognized in ameliorating cognitive impairment and Alzheimer's disease (AD), especially the progression of cognitive dysfunction. But the underlying mechanism is still unclear.

OBJECTIVE

This study was designed to determine the role of green tea consumption in the association with cerebrospinal fluid (CSF) biomarkers of AD pathology and to ascertain whether specific population backgrounds showed the differences toward these relationships.

METHODS

Multivariate linear models analyzed the available data on CSF biomarkers and frequency of green tea consumption of 722 cognitively intact participants from the Chinese Alzheimer's Biomarker and LifestylE (CABLE) database, and we additionally detected the interaction effects of tea consumption with APOEɛ4 status and gender using a two-way analysis of covariance.

RESULTS

Frequent green tea consumption was associated with a decreased level of CSF total-tau protein (t-tau) (p = 0.041) but not with the levels of CSF amyloid-β 42 (Aβ42) and CSF phosphorylated tau. The more pronounced associations of green tea consumption with CSF t-tau (p = 0.007) and CSF t-tau/Aβ42 (p = 0.039) were observed in individuals aged 65 years or younger. Additionally, males with frequent green tea consumption had a significantly low level of CSF t-tau/Aβ42 and a modest trend toward decreased CSF t-tau. There were no interaction effects of green tea consumption with APOEɛ4 and gender.

CONCLUSION

Collectively, our findings consolidated the favorable effects of green tea on the mitigation of AD risk. The constituents of green tea may improve abnormal tau metabolism and are promising targets in interventions and drug therapies.

Herbal drugs and natural bioactive products as potential therapeutics: A review on pro-cognitives and brain boosters perspectives

Memory, one of the most vital aspects of the human brain, is necessary for the effective survival of an individual. 'Memory' can be defined in various ways but in an overall view, memory is the retention of the information that the brain grasps. Different factors are responsible for the disbalance in the brain's hippocampus region and the acetylcholine level, which masters the memory and cognitive functions. Plants are a source of pharmacologically potent drug molecules of high efficacy. Recently herbal medicine has evolved rapidly, gaining great acceptance worldwide due to their natural origin and fewer side effects. In this review, the authors have discussed the mechanisms and pharmacological action of herbal bioactive compounds to boost memory. Moreover, this review presents an update of different herbs and natural products that could act as memory enhancers and how they can be potentially utilized in the near future for the treatment of severe brain disorders. In addition, the authors also discuss the differences in biological activity of the same herb and emphasize the requirement for a higher standardization in cultivation methods and plant processing. The demand for further studies evaluating the interactions of herbal drugs is mentioned.

Quantification of tea-derived catechins without the requirement for respective calibration curves by single reference liquid chromatography based on relative molar sensitivity

BACKGROUND

Many studies report the monitoring of catechins in tea samples by chromatographic techniques. Unfortunately, only a small number of screening assays for catechins exist as a result of the complexity of authentic standards for the respective calibration curves. In the present study, a single reference (SR) exhaustive assay for the simultaneous quantification of tea-derived catechins by liquid chromatography (LC) with photodiode array and fluorescence detectors based on relative molar sensitivity (RMS) was developed as a screening assay of common tea samples without respective calibration curves using authentic standards.

RESULTS

Three original SR standards were proposed based on flavonoid structures, evaluated by quantitative ¹ H-NMR based on an indirect standard (1,4-bis(trimethylsilyl) benzene-d₄ ) and successfully separated in a LC chromatogram. In tea samples with these added SR calculated based on RMS, the concentrations of eight tea-derived catechins could be measured with a relative SD of < 8.5% by a single LC run.

CONCLUSION

This LC screening assay based on RMS allows reliable quantification without the requirement for respective calibration curves using authentic standards. © 2020 Society of Chemical Industry.

On-line coupling pressurised liquid extraction with two-dimensional counter current chromatography for isolation of natural acetylcholinesterase inhibitors from Astragalus membranaceus

INTRODUCTION

Radix Astragali, the dried root of Astragalus membranaceus (Fish.) Bge. (family Fabaceae), which is known as Huangqi in China, has been proven to be an immunostimulant, diuretic, antidiabetic, analgesic, and it has also been used as a health food supplement in some Asian populations and also serves as a lead herb in many traditional Chinese medicine formulations as well as in Chinese ethnic tonifying soups.

OBJECTIVE

Screening and purification of bioactive compounds from natural products is challenging work due to their complexity. We present the first report on the use of pressurised liquid extraction and on-line two-dimensional counter current chromatography as an efficient medium for scaled-up extraction and separation of six bioactive compounds from Astragalus membranaceus.

METHOD

We applied the established method with ultrafiltration-liquid chromatography to screen acetylcholinesterase inhibitors, which were then evaluated and confirmed for anti-Alzheimer activity using PC12 cell model.

RESULTS

Six major compounds, namely, calycosin-7-O-β-d-glucoside, pratensein-7-O-β-d-glucoside, formononetin-7-O-β-d-glucoside, calycosin, genistein, and formononetin, with acetylcholinesterase binding affinities were identified and isolated from the raw plant materials via two sets of n-hexane/ethyl acetate/0.2% acetic acid (first-stage counter current chromatography) and n-hexane/ethyl acetate/methanol/water (second-stage counter current chromatography) solvent systems: 1.87:1.0:1.33 and 5.62:1.0:2.42:5.25, v/v/v/v, which were optimised by a mathematical model.

CONCLUSION

Therefore, a useful platform for the large-scale production of bioactive and nutraceutical ingredients was developed herein. With the on-line system developed here, we present a feasible, selective, and effective strategy for rapid screening and identification of enzyme inhibitors from complex mixtures.

A review on α-mangostin as a potential multi-target-directed ligand for Alzheimer's disease

Alzheimer's disease (AD) is an age-related neurodegenerative disease characterized by progressive memory loss, declining language skills and other cognitive disorders. AD has brought great mental and economic burden to patients, families and society. However due to the complexity of AD's pathology, drugs developed for the treatment of AD often fail in clinical or experimental trials. The main problems of current anti-AD drugs are low efficacy due to mono-target method or side effects, especially high hepatotoxicity. To tackle these two main problems, multi-target-directed ligand (MTDL) based on "one molecule, multiple targets" has been studied. MTDLs can regulate multiple biological targets at the same time, so it has shown higher efficacy, better safety. As a natural active small molecule, α-mangostin (α-M) has shown potential multi-factor anti-AD activities in a series of studies, furthermore it also has a certain hepatoprotective effect. The good availability of α-M also provides support for its application in clinical research. In this work, multiple activities of α-M related to AD therapy were reviewed, which included anti-cholinesterase, anti-amyloid-cascade, anti-inflammation, anti-oxidative stress, low toxicity, hepatoprotective effects and drug formulation. It shows that α-M is a promising candidate for the treatment of AD.

Neuroprotective effects of the Chrysophyllum perpulchrum extract against an Alzheimer-like rat model of β amyloid1-40 intrahippocampal injection

Objective

Alzheimer’s disease (AD) is a threatening disease for African populations in the upcoming years because of the increase in their expectancy of life. Here, we investigated whether natural products from Chrysophyllum perpulchrum as catechin and two dimeric procyanidins (catechin + hexose) could prevent progression of oxidative stress and cognitive changes using an AD-like rat model induced by Aβ_1-40 injection into the hippocampal CA1 subfield.

Methodology

Adult male Wistar rats were either microinjected with 1% ammonia as a vehicle (10 µL) or aggregated Aβ_1-40 at 10 µg bilateral hippocampus. On the 14th day of post-surgery, some Aβ rats were treated with melatonin (10 mg/kg i.p.) or with the Chrysophyllum perpulchrum extract (300 mg/kg p.o.), and some sham-operated rats received the extract alone. Cognitive abilities were tested with Y-maze, object recognition test and Morris Water Maze. Oxidative stress markers as well as the level of activated microglial cells were assayed in the brain.

Results

Aβ rats exhibited significant deficits of recognition memory and spatial learning. This was associated with an increase of microglia Iba 1 immunoreactivity as well as nitric oxide (NO), malondialdehyde and superoxide dismutase levels but not to the thiol content in the hippocampus, prefrontal cortex and septum of AD-like rats. The Chrysophyllum perpulchrum extract treatment mitigated Aβ-induced cognitive impairments and reversed microglia overactivation and subsequent generation of oxidative stress markers. Interestingly, the neuroprotective actions of the Chrysophyllum perpulchrum extract seem to be comparable to the control drug melatonin used albeit with some more beneficial effects.

Conclusion

These findings are preliminary and should be strengthened by more pharmacological studies of bioactive compounds of Chrysophyllum perpulchrum before being proposed as a promising drug against AD.

Isolation of Neuroprotective Anthocyanins from Black Chokeberry (Aronia melanocarpa) against Amyloid-β-Induced Cognitive Impairment

Black chokeberry (Aronia melanocarpa) fruits are rich in anthocyanins, which are vital secondary metabolites that possess antioxidative properties. The aim of this study was to isolate and purify the anthocyanins from black chokeberry by simulated moving bed (SMB) chromatography, and to investigate the neuroprotective effect of SMB purified anthocyanin against Aβ-induced memory damage in rats. The parameters of the SMB process were studied and optimized. Anthocyanin extracts were identified by HPLC and UPLC-QTOF-MS, and antioxidant abilities were evaluated. The Aβ-induced animal model was established by intracerebral ventricle injection in rat brain. Through the SMB purification, anthocyanins were purified to 85%; cyanidin 3-O-galactoside and cyanidin 3-O-arabinoside were identified as the main anthocyanins by UPLC-QTOF-MS. The SMB purified anthocyanins exhibited higher DPPH and ABTS free radical scavenging abilities than the crude anthocyanins extract. Furthermore, rats receiving SMB purified anthocyanins treatment (50 mg/kg) showed improved spatial memory in a Morris water maze test, as well as protection of the cells in the hippocampus against Aβ toxicity. These results demonstrate that anthocyanins could serve as antioxidant and neuroprotective agents, with potential in the treatment of Alzheimer's disease.

Strength training or green tea prevent memory deficits in a β-amyloid peptide-mediated Alzheimer's disease model

Antioxidant supplementation and physical exercise have been discussed as strategies to minimize neurodegeneration in Alzheimer's disease (AD). We investigated the neuroprotective effects of strength exercise (StrEx) and green tea (GT) supplementation, combined or not, on memory impairments induced by β-amyloid characterizing an AD-like condition in rats. Wistar rats were submitted to 8 weeks of StrEx, GT supplementation, or StrEx and GT combined. AD-like condition was induced by injection of Aβ (25-35) in the hippocampus. We evaluate object recognition (OR) and social recognition (SR) memory, and removed the rats' hippocampus for biochemical analysis. StrEx improved OR and SR. StrEx combined with GT improved OR and did not improve SR. GT reduced antioxidant capacity and improved acetylcholinesterase activity. Both strength exercise and green tea are neuroprotective against impairments resultant of β-amyloid, but benefits do not add up when the two interventions are associated.

Catechins as Tools to Understand the Molecular Basis of Neurodegeneration

Protein misfolding as well as the subsequent self-association and deposition of amyloid aggregates is implicated in the progression of several neurodegenerative disorders including Alzheimer's and Parkinson's diseases. Modulators of amyloidogenic aggregation serve as essential tools to dissect the underlying molecular mechanisms and may offer insight on potential therapeutic solutions. These modulators include green tea catechins, which are potent inhibitors of amyloid aggregation. Although catechins often exhibit poor pharmacokinetic properties and bioavailability, they are still essential tools for identifying the drivers of amyloid aggregation and for developing other aggregation modulators through structural mimicry. As an illustration of such strategies, here we review how catechins have been used to map the toxic surfaces of oligomeric amyloid-like species and develop catechin-based phenolic compounds with enhanced anti-amyloid activity.

Potential effect of herbal antidepressants on cognitive deficit: Pharmacological activity and possible molecular mechanism

ETHNOPHARMACOLOGICAL RELEVANCE

Cognitive symptom is a "core" symptom of major depressive disorder (MDD) patients with clear deficit in memory, social and occupational function, and may persist during the remitting phase. Therefore, the remission of cognitive symptom has been considered as one of the main objectives in the treatment of MDD. Herbal antidepressants have been used to treat MDD, and there has been great advances in the understanding of the ability of these herbs to improve cognitive deficit linked to brain injury and various diseases including depression, Alzheimer disease, diabetes and age-related disorders. This systematic review summarizes the evidence from preclinical studies and clinical trials of herbal antidepressants with positive effects on cognitive deficit. The potential mechanisms by which herbal antidepressants prevent cognitive deficit are also reviewed. This review will facilitate further research and applications.

MATERIALS AND METHODS

We conducted an open-ended, English restricted search of MEDLINE (PubMed), Web of Science and Scopus for all available articles published or online before 31 December 2019, using terms pertaining to medical herb/phytomedicine/phytochemical/Chinese medicine and depression/major depressive disorder/antidepressant and/or cognitive impairment/cognitive deficit/cognitive dysfunction.

RESULTS

7 prescriptions, more than 30 individual herbs and 50 phytochemicals from China, Japan, Korea and India with positive effects on the depressive state and cognitive deficit are reviewed herein. The evidence from preclinical studies and clinical trials proves that these herbal antidepressants exhibit positive effects on one or more aspects of cognitive defect including spatial, episodic, aversive, and short- and long-term memory. The action mode of the improvement of cognitive deficit by these herbal antidepressants is mediated mainly through two pathways. One pathway is to promote hippocampal neurogenesis through activating brain derived neurotrophic factor-tropomyosin-related kinase B signaling. The other pathway is to prevent neuronal apoptosis through the inhibition of neuro-inflammation and neuro-oxidation.

CONCLUSION

These herbal antidepressants, having potential therapy for cognitive deficit, may prevent pathological processes of neurodegenerative diseases. Furthermore, these herbal medicines should provide a treasure trove, which will accelerate the development of new antidepressants that can effectively improve cognitive symptom in MDD. Studies on their molecular mechanisms may provide more potential targets and therapeutic approaches for new drug discovery.

Protective Effects of Some Grapevine Polyphenols against Naturally Occurring Neuronal Death

The interest in the biological properties of grapevine polyphenols (PPs) in neuroprotection is continuously growing in the hope of finding translational applications. However, there are several concerns about the specificity of action of these molecules that appear to act non-specifically on the permeability of cellular membranes. Naturally occurring neuronal death (NOND) during cerebellar maturation is a well characterized postnatal event that is very useful to investigate the death and rescue of neurons. We here aimed to establish a baseline comparative study of the potential to counteract NOND of certain grapevine PPs of interest for the oenology. To do so, we tested ex vivo the neuroprotective activity of peonidin- and malvidin-3-O-glucosides, resveratrol, polydatin, quercetin-3-O-glucoside, (+)-taxifolin, and (+)-catechin. The addition of these molecules (50 μM) to organotypic cultures of mouse cerebellum explanted at postnatal day 7, when NOND reaches a physiological peak, resulted in statistically significant (two-tailed Mann-Whitney test-p < 0.001) reductions of the density of dead cells (propidium iodide+ cells/mm2) except for malvidin-3-O-glucoside. The stilbenes were less effective in reducing cell death (to 51-60%) in comparison to flavanols, (+)-taxifolin and quercetin 3-O-glucoside (to 69-72%). Thus, molecules with a -OH group in ortho position (taxifolin, quercetin 3-O-glucoside, (+)-catechin, and peonidin 3-O-glucoside) have a higher capability to limit death of cerebellar neurons. As NOND is apoptotic, we speculate that PPs act by inhibiting executioner caspase 3.

Regardless of the Brewing Conditions, Various Types of Tea are a Source of Acetylcholinesterase Inhibitors

Alzheimer’s disease (AD) is a progressive neurodegenerative disease characterized, among others, by abnormally low levels of the neurotransmitter acetylcholine in the brain. Acetylcholinesterase (AChE) plays a significant role in the process through hydrolysis of the acetylcholine neurotransmitter. Currently, the main method for treatment of AD at a symptomatic stage entails administration of AChE inhibitors to patients diagnosed with the disease. However, it is also possible to take certain steps to treat AD by delivering inhibitors with food. There is a growing body of evidence to suggest that tea (Camellia sinensis) shows numerous beneficial properties, including improving cognitive abilities. This is particularly important in the case of AD patients. The study assessed the impact of brewing conditions on the inhibition of AChE activity observed in tea extracts (black, white, or fruit). Our study revealed that neither temperature nor time of brewing influenced the respective infusions’ ability to inhibit the activity of AChE. Anticholinesterase activity was observed in most of the different types of tea that were analyzed, with the highest rate of inhibition (30.46%–48.54%) evidenced in the Biofix Tea Wild Strawberry brand. The results of our research show that tea may be used as a rich source of cholinesterase inhibitors which play a significant role in AD treatment.

Polyphenols from Food and Natural Products: Neuroprotection and Safety

Polyphenols are naturally occurring micronutrients that are present in many food sources. Besides being potent antioxidants, these molecules may also possess anti-inflammatory properties. Many studies have highlighted their potential role in the prevention and treatment of various pathological conditions connected to oxidative stress and inflammation (e.g., cancer, and cardiovascular and neurodegenerative disorders). Neurodegenerative diseases are globally one of the main causes of death and represent an enormous burden in terms of human suffering, social distress, and economic costs. Recent data expanded on the initial antioxidant-based mechanism of polyphenols’ action by showing that they are also able to modulate several cell-signaling pathways and mediators. The proposed benefits of polyphenols, either as protective/prophylactic substances or as therapeutic molecules, may be achieved by the consumption of a natural polyphenol-enriched diet, by their use as food supplements, or with formulations as pharmaceutical drugs/nutraceuticals. It has also been proved that the health effects of polyphenols depend on the consumed amount and their bioavailability. However, their overconsumption may raise safety concerns due to the accumulation of high levels of these molecules in the organism, particularly if we consider the loose regulatory legislation regarding the commercialization and use of food supplements. This review addresses the main beneficial effects of food polyphenols, and focuses on neuroprotection and the safety issues related to overconsumption.

Natural Products and Their Therapeutic Effect on Autism Spectrum Disorder

Autism is a complex neurodevelopmental disorder that is evident in early childhood and can persist throughout the entire life. The disease is basically characterized by hurdles in social interaction where the individuals demonstrate repetitive and stereotyped interests or patterns of behavior. A wide number of neuroanatomical studies with autistic patients revealed alterations in brain development which lead to diverse cellular and anatomical processes including atypical neurogenesis, neuronal migration, maturation, differentiation, and degeneration. Special education programs, speech and language therapy, have been employed for the amelioration of behavioral deficits in autism. Although commonly prescribed antidepressants, antipsychotics, anticonvulsants, and stimulants have revealed satisfactory responses in autistic individuals, adverse side effects and increased risk of several other complications including obesity, dyslipidemia, diabetes mellitus, thyroid disorders, etc. have compelled the researchers to turn their attention toward herbal remedies. Alternative approaches with natural compounds are on continuous clinical trial to confirm their efficacy and to understand their potential in autism treatment. This chapter aims to cover the major plant-based natural products which hold promising outcomes in the field of reliable therapeutic interventions for autism.

Health Functions and Related Molecular Mechanisms of Tea Components: An Update Review

Tea is widely consumed all over the world. Generally, tea is divided into six categories: White, green, yellow, oolong, black, and dark teas, based on the fermentation degree. Tea contains abundant phytochemicals, such as polyphenols, pigments, polysaccharides, alkaloids, free amino acids, and saponins. However, the bioavailability of tea phytochemicals is relatively low. Thus, some novel technologies like nanotechnology have been developed to improve the bioavailability of tea bioactive components and consequently enhance the bioactivity. So far, many studies have demonstrated that tea shows various health functions, such as antioxidant, anti-inflammatory, immuno-regulatory, anticancer, cardiovascular-protective, anti-diabetic, anti-obesity, and hepato-protective effects. Moreover, it is also considered that drinking tea is safe to humans, since reports about the severe adverse effects of tea consumption are rare. In order to provide a better understanding of tea and its health potential, this review summarizes and discusses recent literature on the bioactive components, bioavailability, health functions, and safety issues of tea, with special attention paid to the related molecular mechanisms of tea health functions.

Effects of Camellia Sinensis Extract on Repeated Restraint Stress-Induced Ovariectomized Female Rats

The mortality of individuals suffering from depression has been increasing, noticeably of postmenopausal women; consequently, their care and treatment are significant to retain a high quality of life. The aim of this study was to examine the effect of Camellia sinensis (CS) on repeated stress-induced changes of the depression related function on the tail suspension test (TST), forced swimming test (FST) in ovariectomized female rats. After behavioral test, we evaluated the changes in the neurotransmitter by measuring the level of dopamine in the nucleus accumbens (NaC) and the serum levels of estrogen and oxytocin. We used 18F-2-fluoro-deoxy-D-glucose positron emission tomography (18F-FDG-PET) to examine the effects of CS on glucose metabolism in ovariectomized rats. Female rats were randomly segregated into three groups. Nor group was considered as nonoperated and nonstressed group, while the control was the ovariectomized and stressed group (OVX+ST), and CS was the ovariectomized, stressed and CS treated group. The rats were exposed to immobilization stress (IMO) for 14 d (2 h/d), and CS (300 mg/kg, i.p.) was treated 30 min before IMO stress. Significant reduction of immobility in the TST and FST was indicated in rats treatment with CS compared to the control group (OVX+ST). The levels of estrogen in the serum of the Nor and CS groups were significantly elevated compared to the OVX+ST group. Also, CS activated brain glucose metabolism in the cortex. The present findings suggested that CS had antidepressant effectiveness in a menopausal depression animal model. These findings suggest evidence that CS plays a crucial role in stressful situation, providing that CS might be a dependable antidepressant medicine to treat menopausal depression.

Phytochemical Composition and Antioxidant Capacity of 30 Chinese Teas

Tea has been reported to prevent and manage many chronic diseases, such as cancer, diabetes, obesity, and cardiovascular diseases, and the antioxidant capacity of tea may be responsible for these health benefits. In this study, the antioxidant capacities of fat-soluble, water-soluble, and bound-insoluble fractions of 30 Chinese teas belonging to six categories, namely green, black, oolong, dark, white, and yellow teas, were systematically evaluated, applying ferric-reducing antioxidant power and Trolox equivalent antioxidant capacity assays. In addition, total phenolic contents of teas were determined by Folin-Ciocalteu method, and the contents of 18 main phytochemical compounds in teas were measured by high-performance liquid chromatography (HPLC). The results found that several teas possessed very strong antioxidant capacity, and caffeine, theaflavine, gallic acid, chlorogenic acid, ellagic acid, and kaempferol-3-O-glucoside, as well as eight catechins, were the main antioxidant compounds in them. Thus, these teas could be good natural sources of dietary antioxidants, and their extracts might be developed as food additives, nutraceuticals, cosmetics, and pharmaceuticals.

Mechanisms Underlying the Anti-Depressive Effects of Regular Tea Consumption

This article is a comprehensive review of the literature pertaining to the antidepressant effects and mechanisms of regular tea consumption. Meta-data supplemented with recent observational studies were first analyzed to assess the association between tea consumption and depression risk. The literature reported risk ratios (RR) were 0.69 with 95% confidence intervals of 0.62-0.77. Next, we thoroughly reviewed human trials, mouse models, and in vitro experiments to determine the predominant mechanisms underlying the observed linear relationship between tea consumption and reduced risk of depression. Current theories on the neurobiology of depression were utilized to map tea-mediated mechanisms of antidepressant activity onto an integrated framework of depression pathology. The major nodes within the network framework of depression included hypothalamic-pituitary-adrenal (HPA) axis hyperactivity, inflammation, weakened monoaminergic systems, reduced neurogenesis/neuroplasticity, and poor microbiome diversity affecting the gut-brain axis. We detailed how each node has subsystems within them, including signaling pathways, specific target proteins, or transporters that interface with compounds in tea, mediating their antidepressant effects. A major pathway was found to be the ERK/CREB/BDNF signaling pathway, up-regulated by a number of compounds in tea including teasaponin, L-theanine, EGCG and combinations of tea catechins and their metabolites. Black tea theaflavins and EGCG are potent anti-inflammatory agents via down-regulation of NF-κB signaling. Multiple compounds in tea are effective modulators of dopaminergic activity and the gut-brain axis. Taken together, our findings show that constituents found in all major tea types, predominantly L-theanine, polyphenols and polyphenol metabolites, are capable of functioning through multiple pathways simultaneously to collectively reduce the risk of depression.

Natural Compounds for Alzheimer's Disease Therapy: A Systematic Review of Preclinical and Clinical Studies

Alzheimer's Disease (AD) is a neurodegenerative disorder related with the increase of age and it is the main cause of dementia in the world. AD affects cognitive functions, such as memory, with an intensity that leads to several functional losses. The continuous increase of AD incidence demands for an urgent development of effective therapeutic strategies. Despite the extensive research on this disease, only a few drugs able to delay the progression of the disease are currently available. In the last years, several compounds with pharmacological activities isolated from plants, animals and microorganisms, revealed to have beneficial effects for the treatment of AD, targeting different pathological mechanisms. Thus, a wide range of natural compounds may play a relevant role in the prevention of AD and have proven to be efficient in different preclinical and clinical studies. This work aims to review the natural compounds that until this date were described as having significant benefits for this neurological disease, focusing on studies that present clinical trials.

Dual-drug loaded nanoparticles of Epigallocatechin-3-gallate (EGCG)/Ascorbic acid enhance therapeutic efficacy of EGCG in a APPswe/PS1dE9 Alzheimer's disease mice model

Epigallocatechin-3-gallate (EGCG) is a candidate for treatment of Alzheimer's disease (AD) but its inherent instability limits bioavailability and effectiveness. We found that EGCG displayed increased stability when formulated as dual-drug loaded PEGylated PLGA nanoparticles (EGCG/AA NPs). Oral administration of EGCG/AA NPs in mice resulted in EGCG accumulation in all major organs, including the brain. Pharmacokinetic comparison of plasma and brain accumulation following oral administration of free or EGCG/AA NPs showed that, whilst in both cases initial EGCG concentrations were similar, long-term (5–25 h) concentrations were ca. 5 fold higher with EGCG/AA NPs. No evidence was found that EGCG/AA NPs utilised a specific pathway across the blood-brain barrier (BBB). However, EGCG, empty NPs and EGCG/AA NPs all induced tight junction disruption and opened the BBB in vitro and ex vivo. Oral treatment of APPswe/PS1dE9 (APP/PS1) mice, a familial model of AD, with EGCG/AA NPs resulted in a marked increase in synapses, as judged by synaptophysin (SYP) expression, and reduction of neuroinflammation as well as amyloid β (Aβ) plaque burden and cortical levels of soluble and insoluble Aβ_(1-42) peptide. These morphological changes were accompanied by significantly enhanced spatial learning and memory. Mechanistically, we propose that stabilisation of EGCG in NPs complexes and a destabilized BBB led to higher therapeutic EGCG concentrations in the brain. Thus EGCG/AA NPs have the potential to be developed as a safe and strategy for the treatment of AD.

A Review of the Role of Green Tea (Camellia sinensis) in Antiphotoaging, Stress Resistance, Neuroprotection, and Autophagy

Tea is one of the most widely consumed beverages worldwide, and is available in various forms. Green tea is richer in antioxidants compared to other forms of tea. Tea is composed of polyphenols, caffeine, minerals, and trace amounts of vitamins, amino acids, and carbohydrates. The composition of the tea varies depending on the fermentation process employed to produce it. The phytochemicals present in green tea are known to stimulate the central nervous system and maintain overall health in humans. Skin aging is a complex process mediated by intrinsic factors such as senescence, along with extrinsic damage induced by external factors such as chronic exposure to ultraviolet (UV) irradiation—A process known as photoaging—Which can lead to erythema, edema, sunburn, hyperplasia, premature aging, and the development of non-melanoma and melanoma skin cancers. UV can cause skin damage either directly, through absorption of energy by biomolecules, or indirectly, by increased production of reactive oxygen species (ROS) and reactive nitrogen species (RNS). Green tea phytochemicals are a potent source of exogenous antioxidant candidates that could nullify excess endogenous ROS and RNS inside the body, and thereby diminish the impact of photoaging. Several in vivo and in vitro studies suggest that green tea supplementation increases the collagen and elastin fiber content, and suppresses collagen degrading enzyme MMP-3 production in the skin, conferring an anti-wrinkle effect. The precise mechanism behind the anti-photoaging effect of green tea has not been explored yet. Studies using the worm model have suggested that green tea mediated lifespan extension depends on the DAF-16 pathway. Apart from this, green tea has been reported to have stress resistance and neuroprotective properties. Its ROS scavenging activity makes it a potent stress mediator, as it can also regulate the stress induced by metal ions. It is known that tea polyphenols can induce the expression of different antioxidant enzymes and hinder the DNA oxidative damage. Growing evidence suggests that green tea can also be used as a potential agent to mediate neurodegenerative diseases, including Alzheimer’s disease. EGCG, an abundant catechin in tea, was found to suppress the neurotoxicity induced by Aβ as it activates glycogen synthase kinase-3β (GSK-3β), along with inhibiting c-Abl/FE65—the cytoplasmic nonreceptor tyrosine kinase which is involved in the development of the nervous system and in nuclear translocation. Additionally, green tea polyphenols induce autophagy, thereby revitalizing the overall health of the organism consuming it. Green tea was able to activate autophagy in HL-60 xenographs by increasing the activity of PI3 kinase and BECLIN-1. This manuscript describes the reported anti-photoaging, stress resistance, and neuroprotective and autophagy properties of one of the most widely known functional foods—green tea.

The in Vivo Antioxidant Effects of (-)-Epigallocatechin-3-Gallate Consumption in Healthy Postmenopausal Women Measured by Urinary Excretion of Secondary Lipid Peroxidation Products

The present study was carried out to determine whether the consumption of epigallocatechin (EGCG), the major bioactive green tea catechin, exerts a positive effect on lowering in vivo lipid peroxidation, a measure of oxidative stress, in healthy postmenopausal women. Urinary excretion of secondary lipid peroxidation products, a measure of in vivo lipid peroxidation, was determined in 40 participants randomly assigned to consume a green tea catechin extract (843.0 ± 44.0 mg EGCG/d) or placebo capsules for 12 months. Urine samples were analyzed for individual polar and nonpolar lipophilic aldehydes and related carbonyl compounds by high-performance liquid chromatography (HPLC) at the beginning and at the end of the 12-month intervention period. Results show that two nonpolar aldehydes, nonanal and decatrienal, were both 48% lower (p < 0.005) following consumption of EGCG. These results indicate that a modest degree of in vivo antioxidant activity exists with long-term EGCG consumption, which could slightly limit oxidative damage associated with lipid peroxidation and the onset and progression of chronic diseases.