Neuroprotection of Ilex latifolia and caffeoylquinic acid derivatives against excitotoxic and hypoxic damage of cultured rat cortical neurons

Quantification of Caffeoylquinic Acids and Triterpenes as Targeted Bioactive Compounds of Centella asiatica in Extracts and Formulations by Liquid Chromatography Mass Spectrometry

Centella asiatica (CA) is a culinary vegetable and well-known functional food that is widely used as a medicinal herb and dietary supplement. CA is rich in pentacyclic triterpenes (TTs), including asiaticoside (AS), madecassoside (MS) and the related aglycones asiatic acid (AA), madecassic acid (MA). Traditionally, TTs have been associated with the bioactivity and health promoting effect of CA. Recently, mono-caffeoylquinic acids (MonoCQAs) and di-caffeoylquinic acids (DiCQAs) have been found to contribute to the bioactivity of CA as well. This work reports an analytical strategy based on liquid chromatography coupled to multiple reaction monitoring mass spectrometry (LC-MRM-MS) for the simultaneous rapid and accurate quantification of 12 bioactive compounds in CA, namely AS, MS, AA, MA, 5-CQA, 4-CQA, 3-CQA, 1,3-DiCQA, 3,4-DiCQA, 1,5-DiCQA, 3,5-DiCQA, 4,5-DiCQA. Method selectivity, accuracy, precision, repeatability, robustness, linearity range, limit of detection (LOD), and limit of quantitation (LOQ) were validated. The validated LC-MRM-MS method has been successfully applied to quantify the 12 bioactive compounds in CA aqueous extracts and two related formulations: a standardized CA product (CAP) used in a phase I clinical trial and formulated CA rodent diets used in preclinical studies. The validated method allows us to support the standardization of CA products used for clinical trials and conduct routine LC-MRM-MS analyses of formulated preclinical diets to confirm correct levels of CA phytochemical markers.

Multispectroscopic and Computational Investigations on the Binding Mechanism of Dicaffeoylquinic Acids with Ovalbumin

Recently, studies on the interactions between ovalbumin (OVA) and polyphenols have received a great deal of interest. This study explored the conformational changes and the interaction mechanism of the binding between OVA and chlorogenic acid (CGA) isomers such as 3,4-dicaffeoylquinic acids (3,4-diCQA), 4,5-dicaffeoylquinic acids (4,5-diCQA), and 3,5-dicaffeoylquinic acids (3,5-diCQA) using multispectroscopic and in silico analyses. The emission spectra show that the diCQAs caused strong quenching of OVA fluorescence under different temperatures through a static quenching mechanism with hydrogen bond (H-bond) and van der Waals (vdW) interactions. The values of binding constants (OVA-3,4-diCQA = 6.123 × 10⁵, OVA-3,5-diCQA = 2.485 × 10⁵, OVA-4,5-diCQA = 4.698 × 10⁵ dm³ mol^-1 at 298 K) suggested that diCQAs had a strong binding affinity toward OVA, among which OVA-3,4-diCQA exhibits higher binding constant. The results of UV-vis absorption and synchronous fluorescence indicated that the binding of all three diCQAs to OVA induced conformational and micro-environmental changes in the protein. The findings of molecular modeling further validate the significant role of vdW force and H-bond interactions in ensuring the stable binding of OVA-diCQA complexes. Temperature-dependent molecular dynamics simulation studies allow estimation of the individual components that contribute to the total bound free energy value, which allows evaluation of the nature of the interactions involved. This research can provide information for future investigations on food proteins' physicochemical stability and CGA bioavailability in vitro or in vivo.

Pharmacokinetics and Pharmacodynamics of Key Components of a Standardized Centella asiatica Product in Cognitively Impaired Older Adults: A Phase 1, Double-Blind, Randomized Clinical Trial

Centella asiatica is reputed in Eastern medicine to improve cognitive function in humans. Preclinical studies have demonstrated that aqueous extracts of C. asiatica improve cognition in mouse models of aging and Alzheimer's disease (AD) through the modulation of mitochondrial biogenesis and nuclear factor-erythroid-2-related factor 2 (Nrf2)-dependent antioxidant response genes. This randomized, double-blind, crossover Phase I trial explored the oral bioavailability and pharmacokinetics of key compounds from two doses (2 g and 4 g) of a standardized C. asiatica aqueous extract product (CAP), over 10 h, in four mildly demented older adults on cholinesterase inhibitor therapy. The analysis focused on triterpenes (TTs) and caffeoylquinic acids (CQAs), which are known to contribute to C. asiatica's neurological activity. The acute safety of CAP and the effects on NRF2 gene expression in peripheral blood mononuclear cells were evaluated. Single administration of 2 g or 4 g of CAP was safe and well-tolerated. The TT aglycones, asiatic acid and madecassic acid, were identified in plasma and urine, while the parent glycosides, asiaticoside and madecassoside, although abundant in CAP, were absent in plasma and had limited renal excretion. Similarly, mono- and di-CQAs showed delayed absorption and limited presence in plasma or urine, while the putative metabolites of these compounds showed detectable plasma pharmacokinetic profiles and urinary excretion. CAP elicited a temporal change in NRF2 gene expression, mirroring the TT aglycone's pharmacokinetic curve in a paradoxical dose-dependent manner. The oral bioavailability of active compounds or their metabolites, NRF2 target engagement, and the acute safety and tolerability of CAP support the validity of using CAP in future clinical studies.

Petasites japonicus leaf extract inhibits Alzheimer's-like pathology through suppression of neuroinflammation

Neuroinflammation is a crucial step involved in development and progression of Alzheimer's disease. The current study found that Petasites japonicus leaf extract inhibits neuroinflammation induced by lipopolysaccharides and amyloid beta oligomers.

The ethnopharmacology, phytochemistry, pharmacology and toxicology of the genus Erycibe (Convolvulaceae)

ETHNOPHARMACOLOGICAL RELEVANCE

The genus Erycibe belongs to the Convolvulaceae family that contains approximately 70 species mainly distributed from tropical and subtropical Asia to north of Australia. Several Erycibe species are traditionally used in folk medicine for the treatment of various ailments, including rheumatic arthralgia, primary glaucoma, hepatopathies, and infectious and malignant diseases.

AIM OF THE REVIEW

This review aims to summarize comprehensive and updated information on traditional medicinal uses, phytochemistry, pharmacology, and toxicology of Erycibe species to provide a reference for the further research and application of the Erycibe genus.

MATERIALS AND METHODS

The scientific and extensive literatures between 1975 and 2020 were systematically gathered from scientific databases such as SciFinder Scholar, Science Direct, Web of Science, PubMed, Google Scholar, Scopus, Springer Link and China National Knowledge Infrastructure (CNKI), as well as Chinese herbal classic books, PhD and MSc theses, and several official websites.

RESULTS

Erycibe species have been used for the treatment of various rheumatoid diseases, glaucoma, a variety of hepatic diseases, infectious diseases and various malignancies in the traditional and local medicine. Since the 1970s, 153 compounds, including coumarins, quinic acid derivatives, flavonoids, alkaloids, lignans, and others have been isolated from five species of the Erycibe genus. Pharmacological studies have shown that these extracts and compounds from the Erycibe genus have extensive activities consistent with the traditional and local applications, such as anti-glaucoma, anti-arthritic, hepatoprotective and anti-cancer activities, as well as anti-inflammatory, anti-respiratory syncytial virus (RSV), and neuroprotective properties.

CONCLUSIONS

Although there are extensive data on the genus Erycibe, certain specific gaps still exist. For herbal preparations containing Erycibe species, clinical toxicological investigation is required for the safety of these herbal preparation therapies, as well as further investigations on pharmacokinetics and bioavailability for guideline for clinical application. Furthermore, more detailed pharmacological, toxicological and clinical researches are needed to assess the alternatives to Erycibe species. Systematic and comprehensive pre-clinical studies are similarly required to estimate the possibility of extracts and compounds from the genus Erycibe with bioactivity developing into new drugs.

Caffeoylquinic acids: chemistry, biosynthesis, occurrence, analytical challenges, and bioactivity

Caffeoylquinic acids (CQAs) are specialized plant metabolites we encounter in our daily life. Humans consume CQAs in mg-to-gram quantities through dietary consumption of plant products. CQAs are considered beneficial for human health, mainly due to their anti-inflammatory and antioxidant properties. Recently, new biosynthetic pathways via a peroxidase-type p-coumaric acid 3-hydroxylase enzyme were discovered. More recently, a new GDSL lipase-like enzyme able to transform monoCQAs into diCQA was identified in Ipomoea batatas. CQAs were recently linked to memory improvement; they seem to be strong indirect antioxidants via Nrf2 activation. However, there is a prevalent confusion in the designation and nomenclature of different CQA isomers. Such inconsistencies are critical and complicate bioactivity assessment since different isomers differ in bioactivity and potency. A detailed explanation regarding the origin of such confusion is provided, and a recommendation to unify nomenclature is suggested. Furthermore, for studies on CQA bioactivity, plant-based laboratory animal diets contain CQAs, which makes it difficult to include proper control groups for comparison. Therefore, a synthetic diet free of CQAs is advised to avoid interferences since some CQAs may produce bioactivity even at nanomolar levels. Biotransformation of CQAs by gut microbiota, the discovery of new enzymatic biosynthetic and metabolic pathways, dietary assessment, and assessment of biological properties with potential for drug development are areas of active, ongoing research. This review is focused on the chemistry, biosynthesis, occurrence, analytical challenges, and bioactivity recently reported for mono-, di-, tri-, and tetraCQAs.

Ilex kudingcha C.J. Tseng Mitigates Phenotypic Characteristics of Human Autism Spectrum Disorders in a Drosophila Melanogaster Rugose Mutant

Autism spectrum disorders (ASD) have heterogeneous etiologies involving dysfunction of central nervous systems, for which no effective pan-specific treatments are available. Ilex kudingcha (IK) C.J. Tseng is a nootropic botanical used in Asia for neuroprotection and improvement of cognition. This study establishes that a chemically characterized extract from IK (IKE) mitigates behavioral traits in the Drosophila melanogaster rugose mutant, whose traits resemble human ASD, and examines possible mechanisms. IKE treatment significantly ameliorated deficits in social interaction, short-term memory, and locomotor activity in Drosophila rugose, and significantly increased synaptic bouton number of size more than 2 μm² in the neuromuscular junctions (NMJs) of Drosophila rugose. To clarify mechanism(s) of IKE action, methylphenidate (MPH), a dopamine transporter inhibitor, was included as a reference drug in the behavioral assays: MPH significantly improved social interaction and short-term memory deficit in Drosophila rugose; administration of the dopamine D1 receptor antagonist SCH23390 and dopamine D2 receptor antagonist sulpiride reversed the ameliorative effects of both MPH and IKE on the social interaction deficits of Drosophila rugose. To extend analysis of IKE treatment to the vertebrate central nervous system, ASD-associated gene expression in mouse hippocampus was studied by RNA-seq: IKE treatment altered the expression of genes coding phosphoinositide 3-kinases/protein kinase B (PI3K-Akt), proteins in glutamatergic, dopaminergic, serotonergic, and GABAergic synapses, cAMP response element-binding protein (CREB), and RNA transporter proteins. These results provide a foundation for further analysis of IKE as a candidate for treatment of some forms of ASD.

In vitro cultivation of tansy (Tanacetum vulgare L.): a tool for the production of potent pharmaceutical agents

In this study, tansy (Tanacetum vulgare L.) in vitro culture was established from seeds collected from natural populations. The multiplication of plantlets was conducted through shoot tips that exhibited potent apical growth and regeneration capacities on basal medium (BM), without the addition of any plant growth regulators (PGRs). PGRs were also omitted for the establishment and cultivation of tansy root cultures. Both abaxial and adaxial leaf surfaces of in vitro micropropagated plantlets were covered with glandular biseriate trichomes. Histochemical staining showed that glandular secretions were rich in lipid and terpene compounds, confirmed by GC-MS analysis of essential oil (EO). In the total EO, similar portions of oxygenated monoterpenes (38.5% m/m) and oxygenated sesquiterpenes (22.6% m/m) were detected. Chemical profiles of methanol extracts of in vitro cultured tansy shoots and roots varied in quantity and quality from those obtained from wild-growingtansy. HPLC analysis indicated that the methanol extracts of in vitro cultured roots were the richest in 3,5-O-dicaffeoylquinic acid (3,5-O-DCQA), in which the concentration was 6 times higher (10.220 mg/g DW) than that in the extract obtained from roots of wild-growing tansy (1.684 mg/g DW). This result is noticeable in the manner of industrial production of biologically active 3,5-O-DCQA that has been shown to have antioxidant, hepatoprotective, antiviral, antimutagenic, and immunomodulatory activity. Biotechnological interventions on secondary metabolite production taking place in trichomes could further enhance the production of some important tansy metabolites and further investigation will be directed toward the elucidation of the pharmaceutical potential of tansy in vitro obtained metabolites, as mixtures or single moieties.

Chemical Structure and Biological Activities of Secondary Metabolites from Salicornia europaea L

Salicornia europaea L. is a halophyte that grows in salt marshes and muddy seashores, which is widely used both as traditional medicine and as an edible vegetable. This salt-tolerant plant is a source of diverse secondary metabolites with several therapeutic properties, including antioxidant, antidiabetic, cytotoxic, anti-inflammatory, and anti-obesity effects. Therefore, this review summarizes the chemical structure and biological activities of secondary metabolites isolated from Salicornia europaea L.

A GDSL lipase-like from Ipomoea batatas catalyzes efficient production of 3,5-diCQA when expressed in Pichia pastoris

The synthesis of 3,5-dicaffeoylquinic acid (3,5-DiCQA) has attracted the interest of many researchers for more than 30 years. Recently, enzymes belonging to the BAHD acyltransferase family were shown to mediate its synthesis, albeit with notably low efficiency. In this study, a new enzyme belonging to the GDSL lipase-like family was identified and proven to be able to transform chlorogenic acid (5-O-caffeoylquinic acid, 5-CQA, CGA) in 3,5-DiCQA with a conversion rate of more than 60%. The enzyme has been produced in different expression systems but has only been shown to be active when transiently synthesized in Nicotiana benthamiana or stably expressed in Pichia pastoris. The synthesis of the molecule could be performed in vitro but also by a bioconversion approach beginning from pure 5-CQA or from green coffee bean extract, thereby paving the road for producing it on an industrial scale.

Miguel et al. identify a new enzyme belonging to the GDSL lipase-like family that is involved in the final stage of transformation of 5-CQA into 3,5-diCQA. This enzyme is able to realize an efficient transformation by over 60%, making the transformation process a valuable technological tool that can be easily transferred on an industrial scale.

Current Advances in Naturally Occurring Caffeoylquinic Acids: Structure, Bioactivity, and Synthesis

Caffeoylquinic acids (CQAs) are a broad class of secondary metabolites that have been found in edible and medicinal plants from various families. It has been 100 years since the discovery of chlorogenic acid in 1920. In recent years, a number of naturally derived CQAs have been isolated and structurally elucidated. Accumulated evidence demonstrate that CQAs have a wide range of biological activities, such as antioxidation, antibacterial, antiparasitic, neuroprotective, anti-inflammatory, anticancer, antiviral, and antidiabetic effects. Up to date, some meaningful progresses on the biosynthesis and total synthesis of CQAs have also been made. Therefore, it is necessary to comprehensively summarize the structure, biological activity, biosynthesis, and chemical synthesis of CQAs. This review provides extensive coverage of naturally occurring CQAs discovered from 1990 until 2020. Modern isolation techniques, chemical data (including structure, biosynthesis, and total synthesis), and bioactivity are summarized. This would be helpful for further research of CQAs as potential pharmaceutical agents.

Chemical Composition, Bioactivity and Safety Aspects of Kuding Tea-From Beverage to Herbal Extract

Kuding tea (KT) is a bitter-tasting herbal tea that has been commonly used in traditional Chinese medicine (TCM). The large-leaved Ku-Ding-Cha (Aquifoliaceae) is composed of its representative species Ilex latifolia Thunb and Ilex kudingcha C.J. Tseng. Because of its potential lipid-lowering, body weight-reducing and blood-glucose-lowering properties, KT has increasingly been recognised for its importance over the past several decades. KT is no longer used only as a beverage, and various extraction methods have been applied to obtain aqueous and ethanolic KT extracts (KTE) or their fractions, which could potentially be used as dietary supplements. The major bioactive components of KT are triterpene saponins and polyphenols, but the composition of KT differs substantially between and among the different KT species. This in turn might affect the physiological effects of KT. KT exhibits antiobesity properties, possibly partly by affecting the intestinal microbiota. In addition, KT may mediate putative antioxidative, anti-inflammatory and anticancer activities. However, there is evidence that high KTE supplementation can adversely affect liver metabolism. The physiological relevance of KT in humans remains rather unclear since the potential health benefits of KT and its constituents reviewed here are mainly derived on the basis of in vitro and animal studies.

Neuroprotective Effects of Medicinal Plants in Cerebral Hypoxia and Anoxia: A Systematic Review

Background:

Hypoxia and anoxia are dangerous and sometimes irreversible complications in the central nervous system (CNS), which in some cases lead to death.

Objective:

The aim of this review was to investigate the neuroprotective effects of medicinal plants in cerebral hypoxia and anoxia.

Methods:

The word hypox*, in combination with some herbal terms such as medicinal plant, phyto* and herb*, was used to search for relevant publications indexed in the Institute for Scientific Information (ISI) and PubMed from 2000-2019.

Results:

Certain medicinal plants and herbal derivatives can exert their protective effects in several ways. The most important mechanisms are the inhibition of inducible nitric oxide synthase (iNOS), production of NO, inhibition of both hypoxia-inducible factor 1α and tumor necrosis factor-alpha activation, and reduction of extracellular glutamate, N-Methyl-D-aspartic and intracellular Ca (2+). In addition, they have an antioxidant activity and can adjust the expression of genes related to oxidant generation or antioxidant capacity. These plants can also inhibit lipid peroxidation, up-regulate superoxide dismutase activity and inhibit the content of malondialdehyde and lactate dehydrogenase. Moreover, they also have protective effects against cytotoxicity through down-regulation of the proteins that causes apoptosis, anti-excitatory activity, inhibition of apoptosis signaling pathway, reduction of pro-apoptotic proteins, and endoplasmic reticulum stress that causes apoptosis during hypoxia, increasing anti-apoptotic protein, inhibition of protein tyrosine kinase activation, decreasing proteases activity and DNA fragmentation, and upregulation of mitochondrial cytochrome oxidase.

Conclusion:

The results indicated that medicinal plants and their compounds mainly exert their neuroprotective effects in hypoxia via regulating proteins that are related to antioxidant, anti-apoptosis and anti-inflammatory activities.

Isochlorogenic Acid A Attenuates the Progression of Liver Fibrosis Through Regulating HMGB1/TLR4/NF-κB Signaling Pathway

Liver fibrosis, a chronic damage process related to further progression of hepatic cirrhosis, has yet no truly effective treatment. Isochlorogenic acid A (ICQA), isolated from a traditional Chinese herbal medicine named Laggera alata (DC.) Sch.Bip. ex Oliv. (Asteraceae), is proved to exhibit anti-inflammatory, hepatoprotective and antiviral properties. However, the actions of ICQA on liver fibrosis are poorly understood. The purpose of this study was to evaluate the actions of ICQA on liver fibrosis and clarify the underlying mechanism. It was found that ICQA had significant protective actions on liver injury, inflammation as we as fibrosis in rats. Meanwhile, ICQA prevented hepatic stellate cells (HSC) activation, indicated by its inhibitory effect on the overexpression of α-smooth muscle actin (α-SMA). In addition, the reduced fibrosis was found to be associated with the decreased protein expression of high-mobility group box 1 (HMGB1) as well as toll like receptor (TLR) 4. Simultaneously, ICQA can suppress the cytoplasmic translocation of HMGB1 in rat liver. Further investigations indicated that ICQA treatment dramatically attenuated the nuclear translocation of the nuclear factor-kB (NF-κB) p65 and suppressed the hepatic expression of p−IκBα in rats with liver fibrosis. Taken together, our study indicated that ICQA could protect against CCl₄-induced liver fibrosis probably through suppressing the HMGB1/TLR4/NF-κB signaling pathways.

Beneficial Effects of Sideritis scardica and Cichorium spinosum against Amyloidogenic Pathway and Tau Misprocessing in Alzheimer's Disease Neuronal Cell Culture Models

BACKGROUND

Natural products are a significantly underutilized source of potential treatments against human disease. Alzheimer's disease (AD) is a prime example of conditions that could be amenable to such treatments as suggested by recent findings.

OBJECTIVE

Aiming to identify novel potentially therapeutic approaches against AD, we assessed the effects of Cichorium spinosum and Sideritis scardica extracts, both distinct components of the Mediterranean diet.

METHODS/RESULTS

After the detailed characterization of the extracts' composition using LC-HRMS methods, they were evaluated on two AD neuronal cell culture models, namely the AβPP overexpressing SH-SY5Y-AβPP and the hyperphosphorylated tau expressing PC12-htau. Initially their effect on cell viability of SH-SY5Y and PC12 cells was examined, and subsequently their downstream effects on AβPP and tau processing pathways were investigated in the SH-SY5Y-AβPP and PC12-htau cells. We found that the S. scardica and C. spinosum extracts have similar effects on tau, as they both significantly decrease total tau, the activation of the GSK3β, ERK1 and/or ERK2 kinases of tau, as well as tau hyperphosphorylation. Furthermore, both extracts appear to promote AβPP processing through the alpha, non-amyloidogenic pathway, albeit through partly different mechanisms.

CONCLUSIONS

These findings suggest that C. spinosum and S. scardica could have a notable potential in the prevention and/or treatment of AD, and merit further investigations at the in vivo level.

Chronic Alcohol Exposure Induced Neuroapoptosis: Diminishing Effect of Ethyl Acetate Fraction from Aralia elata

An ethyl acetate fraction from Aralia elata (AEEF) was investigated to confirm its neuronal cell protective effect on ethanol-induced cytotoxicity in MC-IXC cells and its ameliorating effect on neurodegeneration in chronic alcohol-induced mice. The neuroprotective effect was examined by methylthiazolyldiphenyl-tetrazolium bromide (MTT) and 2',7'-dichlorodihydrofluorescein diacetate (DCF-DA) assays. As a result, AEEF reduced alcohol-induced cytotoxicity and oxidative stress. To evaluate the improvement of learning, memory ability, and spatial cognition, Y-maze, passive avoidance, and Morris water maze tests were conducted. The AEEF groups showed an alleviation of the decrease in cognitive function in alcohol-treated mice. Then, malondialdehyde (MDA) levels and the superoxide dismutase (SOD) content were measured to evaluate the antioxidant effect of AEEF in the brain tissue. Treatment with AEEF showed a considerable ameliorating effect on biomarkers such as SOD and MDA content in alcohol-induced mice. To assess the cerebral cholinergic system involved in neuronal signaling, acetylcholinesterase (AChE) activity and acetylcholine (ACh) content were measured. The AEEF groups showed increased ACh levels and decreased AChE activities. In addition, AEEF prevented alcohol-induced neuronal apoptosis via improvement of mitochondrial activity, including reactive oxygen species levels, mitochondrial membrane potential, and adenosine triphosphate content. AEEF inhibited apoptotic signals by regulating phosphorylated c-Jun N-terminal kinases (p-JNK), phosphorylated protein kinase B (p-Akt), Bcl-2-associated X protein (BAX), and phosphorylated Tau (p-Tau). Finally, the bioactive compounds of AEEF were identified as caffeoylquinic acid (CQA), 3,5-dicaffeoylquinic acid (3,5-diCQA), and chikusetsusaponin IVa using the UPLC-Q-TOF-MS system.

Health Benefits of Bioactive Compounds from the Genus Ilex, a Source of Traditional Caffeinated Beverages

Tea and coffee are caffeinated beverages commonly consumed around the world in daily life. Tea from Camellia sinensis is widely available and is a good source of caffeine and other bioactive compounds (e.g., polyphenols and carotenoids). Other tea-like beverages, such as those from the genus Ilex, the large-leaved Kudingcha (Ilex latifolia Thunb and Ilex kudingcha C.J. Tseng), Yerba Mate (Ilex paraguariensis A. St.-Hil), Yaupon Holly (Ilex vomitoria), and Guayusa (Ilex guayusa Loes) are also traditional drinks, with lesser overall usage, but have attracted much recent attention and have been subjected to further study. This review summarizes the distribution, composition, and health benefits of caffeinated beverages from the genus Ilex. Plants of this genus mainly contain polyphenols and alkaloids, and show diverse health benefits, which, as well as supporting their further popularization as beverages, may also lead to potential applications in the pharmaceutical or nutraceutical industries.

Butterbur Leaves Attenuate Memory Impairment and Neuronal Cell Damage in Amyloid Beta-Induced Alzheimer's Disease Models

Alzheimer’s disease (AD) is the most prevalent neurodegenerative disease, and is characterized by the accumulation of amyloid beta (Aβ) as a pathological hallmark. Aβ plays a central role in neuronal degeneration and synaptic dysfunction through the generation of excessive oxidative stress. In the present study, we explored whether leaves of Petasites japonicus (Siebold & Zucc.) Maxim. (PL), called butterbur and traditionally used in folk medicine, show neuroprotective action against Aβ_25–35 plaque neurotoxicity in vitro and in vivo. We found that PL protected Aβ_25–35 plaque-induced neuronal cell death and intracellular reactive oxygen species generation in HT22 cells by elevating expression levels of phosphorylated cyclic AMP response element-binding protein, heme oxygenase-1, and NAD(P)H quinine dehydrogenase 1. These neuroprotective effects of PL were also observed in Aβ_25–35 plaque-injected AD mouse models. Moreover, administration of PL diminished Aβ_25–35 plaque-induced synaptic dysfunction and memory impairment in mice. These findings lead us to suggest that PL can protect neurons against Aβ_25–35 plaque-induced neurotoxicity and thus may be a potential candidate to regulate the progression of AD.

Development and Validation of a HPLC Method for Determination of Isochlorogenic Acid A in Rat Plasma and Application to Pharmacokinetic Study

A simple, optimized and sensitive high-performance liquid chromatograph method with ultraviolet (UV) detection (HPLC/UV) was developed and validated for determination of isochlorogenic acid A in rat plasma. The analytes were successfully separated on a Shodex C18 column (5 μm particle size, 250 mm × 4.6 mm, i.d.), the mobile phase contained 0.1% phosphoric acid aqueous solution (solvent A) and methanol (solvent B) (50:50, v/v) at a flow rate of 1.0 mL/min. The wavelength for UV detection was set at 300 nm and the column temperature was maintained in 30°C. Calibration curve for isochlorogenic acid A was found to be good linear over the range of 0.04-40 μg/mL (r = 0.9998). The intra- and inter-day precisions (relative standard deviation) were within 7.63% and the assay accuracy (RE) ranged from -1.41 to 3.25%. The limit of detection and the lower limit of quantification were 0.012 and 0.04 μg/mL, respectively. The validated method was successfully applied to pharmacokinetic study of isochlorogenic acid A in rats for the first time. The pharmacokinetic parameters were evaluated after the rats were administered intravenously and intragastrically isochlorogenic acid A at the single dose of 18 mg/kg, respectively. The absolute bioavailability was calculated to be 22.6%.

Bioactivity-guided isolation of neuritogenic triterpenoids from the leaves of Ilex latifolia Thunb

Ilex latifolia Thunb is a traditional Chinese tea and herbal medicine. In this study, one new triterpene saponin (1) and six known triterpenoids (2-7) were isolated from the methanol extract of I. latifolia using a PC12 cell bioassay system. The structures and stereochemistry of these compounds were elucidated using spectroscopic methods and chemical derivatization. This new triterpene saponin (1) was characterized as an ursolic type acid with a 19α-hydroxyl and a trisaccharide moiety at C-3. Compound 1 significantly promoted the neurite outgrowth in PC12 cells by 52% at 10 μM, whereas compounds 2-7 showed less neuritogenic activity. Structure activity relationship studies indicated that introducing a trisaccharide moiety at C-3 is important for the neuritogenic activity, but the sugar group at C-28 decreased this activity. In addition, compound 1 increased the neurite outgrowth length in primary cortical neuron cells of mice and also exhibited a neuronal protection effect on H₂O₂-damaged PC12 cells at optimum concentrations.

Centella asiatica - Phytochemistry and mechanisms of neuroprotection and cognitive enhancement

This review describes in detail the phytochemistry and neurological effects of the medicinal herb Centella asiatica (L.) Urban. C. asiatica is a small perennial plant that grows in moist, tropical and sub-tropical regions throughout the world. Phytochemicals identified from C. asiatica to date include isoprenoids (sesquiterpenes, plant sterols, pentacyclic triterpenoids and saponins) and phenylpropanoid derivatives (eugenol derivatives, caffeoylquinic acids, and flavonoids). Contemporary methods for fingerprinting and characterization of compounds in C. asiatica extracts include liquid chromatography and/or ion mobility spectrometry in conjunction with high-resolution mass spectrometry. Multiple studies in rodent models, and a limited number of human studies support C. asiatica's traditional reputation as a cognitive enhancer, as well as its anxiolytic and anticonvulsant effects. Neuroprotective effects of C.asiatica are seen in several in vitro models, for example against beta amyloid toxicity, and appear to be associated with increased mitochondrial activity, improved antioxidant status, and/or inhibition of the pro-inflammatory enzyme, phospholipase A2. Neurotropic effects of C. asiatica include increased dendritic arborization and synaptogenesis, and may be due to modulations of signal transduction pathways such as ERK1/2 and Akt. Many of these neurotropic and neuroprotective properties of C.asiatica have been associated with the triterpene compounds asiatic acid, asiaticoside and madecassoside. More recently, caffeoylquinic acids are emerging as a second important group of active compounds in C. asiatica, with the potential of enhancing the Nrf2-antioxidant response pathway. The absorption, distribution, metabolism and excretion of the triterpenes, caffeoylquinic acids and flavonoids found in C. asiatica have been studied in humans and animal models, and the compounds or their metabolites found in the brain. This review highlights the remarkable potential for C. asiatica extracts and derivatives to be used in the treatment of neurological conditions, and considers the further research needed to actualize this possibility.

Ilex latifolia Prevents Amyloid β Protein (25-35)-Induced Memory Impairment by Inhibiting Apoptosis and Tau Phosphorylation in Mice

Ilex latifolia Thunb. (Aquifoliaceae), a Chinese bitter tea called "kudingcha," has been widely consumed as a health beverage and found to possess antioxidant, antidiabetic, antihypertensive, anti-inflammatory, and anti-ischemic activities. The aim of the present study was to investigate the neuroprotective effects of an ethanol extract of I. latifolia against amyloid β protein (Aβ)-induced memory impairment in mice and neurotoxicity in cultured rat cortical neurons. Memory impairment in mice was induced by intracerebroventricular injection of 15 nmol Aβ (25-35) and measured by the passive avoidance test and Morris water maze test. Chronic administration of I. latifolia (25-100 mg/kg, p.o.) significantly prevented Aβ (25-35)-induced memory loss. I. latifolia also prevented the decrease of glutathione concentrations, increased lipid peroxidation, expression of phosphorylated tau (p-tau), and changes in apoptosis-associated proteins in the memory-impaired mouse brain. Exposure of cultured cortical neurons to 10 μM Aβ (25-35) for 36 h induced neuronal apoptotic death. The neuronal cell death, elevation of intracellular Ca(2+) concentration, generation of reactive oxygen species, and expression of proapoptotic proteins caused by Aβ (25-35) in the cultured neurons were inhibited by treatment with I. latifolia (1-50 μg/mL). These results suggest that I. latifolia may have a possible therapeutic role in managing cognitive impairment associated with Alzheimer's disease. The underlying mechanism might involve the antiapoptotic effects mediated by antioxidant activity and inhibition of p-tau formation.

Caffeoylquinic acids in Centella asiatica protect against amyloid-β toxicity

The accumulation of amyloid-β (Aβ) is a hallmark of Alzheimer's disease and is known to result in neurotoxicity both in vivo and in vitro. We previously demonstrated that treatment with the water extract of Centella asiatica (CAW) improves learning and memory deficits in Tg2576 mice, an animal model of Aβ accumulation. However the active compounds in CAW remain unknown. Here we used two in vitro models of Aβ toxicity to confirm this neuroprotective effect and identify several active constituents of the CAW extract. CAW reduced Aβ-induced cell death and attenuated Aβ-induced changes in tau expression and phosphorylation in both the MC65 and SH-SY5Y neuroblastoma cell lines. We confirmed and quantified the presence of several mono- and dicaffeoylquinic acids (CQAs) in CAW using chromatographic separation coupled to mass spectrometry and ultraviolet spectroscopy. Multiple dicaffeoylquinic acids showed efficacy in protecting MC65 cells against Aβ-induced cytotoxicity. Isochlorogenic acid A and 1,5-dicaffeoylquinic acid were found to be the most abundant CQAs in CAW, and the most active in protecting MC65 cells from Aβ-induced cell death. Both compounds showed neuroprotective activity in MC65 and SH-SY5Y cells at concentrations comparable to their levels in CAW. Each compound not only mitigated Aβ-induced cell death, but was able to attenuate Aβ-induced alterations in tau expression and phosphorylation in both cell lines, as seen with CAW. These data suggest that CQAs are active neuroprotective components in CAW, and therefore are important markers for future studies on CAW standardization, bioavailability, and dosing.

Role of histidine/histamine in carnosine-induced neuroprotection during ischemic brain damage

Urgent need exists for new therapeutic options in ischemic stroke. We recently demonstrated that carnosine, an endogenous dipeptide consisting of alanine and histidine, is robustly neuroprotective in ischemic brain injury and has a wide clinically relevant therapeutic time window. The precise mechanistic pathways that mediate this neuroprotective effect are not known. Following in vivo administration, carnosine is hydrolyzed into histidine, a precursor of histamine. It has been hypothesized that carnosine may exert its neuroprotective activities through the histidine/histamine pathway. Herein, we investigated whether the neuroprotective effect of carnosine is mediated by the histidine/histamine pathway using in vitro primary astrocytes and cortical neurons, and an in vivo rat model of ischemic stroke. In primary astrocytes, carnosine significantly reduced ischemic cell death after oxygen-glucose deprivation, and this effect was abolished by histamine receptor type I antagonist. However, histidine or histamine did not exhibit a protective effect on ischemic astrocytic cell death. In primary neuronal cultures, carnosine was found to be neuroprotective but histamine receptor antagonists had no effect on the extent of neuroprotection. The in vivo effect of histidine and carnosine was compared using a rat model of ischemic stroke; only carnosine exhibited neuroprotection. Taken together, our data demonstrate that although the protective effects of carnosine may be partially mediated by activity at the histamine type 1 receptor on astrocytes, the histidine/histamine pathway does not appear to play a critical role in carnosine induced neuroprotection.

Neuroprotective evaluation of Tilia americana and Annona diversifolia in the neuronal damage induced by intestinal ischemia

Tilia americana and Annona diversifolia are plants widely distributed in Mexico and sold in markets for their medicinal properties on the central nervous system (CNS) including possible neuroprotection. Pharmacological studies have corroborated CNS activities due to flavonoid constituents, but evidence of their neuroprotector effects are lacking. This study was conducted to test aqueous and organic extracts of these two plants for neuroprotective effects in a novel experimental model of intestinal ischemia in situ. T. americana and A. diversifolia aqueous and organic extracts were administrated to guinea pigs at an oral dose of 100 and 300 mg/kg for 15 days. Twenty four hours after the last administration, the animals were anesthetized and intestinal ischemia in situ was induced by clamping for 80 min selected branches of the superior mesenteric artery. Ischemic segments placed in an in vitro organ bath were stimulated electrically (0.3 Hz frequency, 3.0 ms duration, 14 V intensity) and chemically (ACh; 1 × 10(-9) to 1×10(-5) M). Neuroprotection was considered present when the depressed contractile response of the ischemic tissue to electrical stimulation was normalized in the treated animals. Results showed that pretreatment with the T. americana hexane and aqueous extracts, but not with those from A. diversifolia, significantly improved responses of the ischemic tissue. These results suggest that T. americana possesses neuroprotective effects against neuronal damage induced by ischemia, and that flavonoids as well as non-polar constituents are involved. Our study supports the use of this plant in folk medicine and suggests its possible effectiveness for stroke prevention.

The large-leaved Kudingcha (Ilex latifolia Thunb and Ilex kudingcha C.J. Tseng): a traditional Chinese tea with plentiful secondary metabolites and potential biological activities

In China, Kudingcha has been used for almost 2,000 years as a tea to quench thirst, remove phlegm, refresh the mind, and improve eyesight. The group of large-leaved Kudingcha is coveted for its potential effects on lipid metabolism, which are attributed to the presence of characteristic ingredients. This contribution reviews studies from the past few decades regarding the plant characteristics, ethnobotanical usages, chemical constituents, and related biological activities of the large-leaved Kudingcha (Ilex latifolia Thunb and Ilex kudingcha C.J. Tseng). Triterpenoids, phenolic acids, flavonoids, and essential oils are the main metabolites in the large-leaved Kudingcha, and these ingredients protect the vascular system, regulate lipid metabolism, and have antioxidant, hypoglycemic, and anti-tumor effects. Moreover, large-leaved Kudingcha shares several properties with the popular green tea and the Yerba maté from South America.