Scavenging effect of extracts of green tea and natural antioxidants on active oxygen radicals

Synthetic and Natural Bioactive Molecules in Balancing the Crosstalk among Common Signaling Pathways in Alzheimer's Disease: Understanding the Neurotoxic Mechanisms for Therapeutic Intervention

The structure and function of the brain greatly rely on different signaling pathways. The wide variety of biological processes, including neurogenesis, axonal remodeling, the development and maintenance of pre- and postsynaptic terminals, and excitatory synaptic transmission, depends on combined actions of these molecular pathways. From that point of view, it is important to investigate signaling pathways and their crosstalk in order to better understand the formation of toxic proteins during neurodegeneration. With recent discoveries, it is established that the modulation of several pathological events in Alzheimer's disease (AD) due to the mammalian target of rapamycin (mTOR), Wnt signaling, 5'-adenosine monophosphate activated protein kinase (AMPK), peroxisome proliferator-activated receptor gamma coactivator 1α (PGC-1α), and sirtuin 1 (Sirt1, silent mating-type information regulator 2 homologue 1) are central to the key findings. These include decreased amyloid formation and inflammation, mitochondrial dynamics control, and enhanced neural stability. This review intends to emphasize the importance of these signaling pathways, which collectively determine the fate of neurons in AD in several ways. This review will also focus on the role of novel synthetic and natural bioactive molecules in balancing the intricate crosstalk among different pathways in order to prolong the longevity of AD patients.

Improving the Extraction of Catechins of Green Tea (Camellia sinensis) by Subcritical Water Extraction (SWE) Combined with Pulsed Electric Field (PEF) or Intense Pulsed Light (IPL) Pretreatment

The aim of this study was to find the optimum condition of pulsed electric field (PEF) and intense pulsed light (IPL) for the enhancement of subcritical water extraction (SWE), which is an eco-friendly extraction method, for extracting tea catechins from green tea leaves (Camellia sinensis). The leaves were treated with PEF under conditions of electric field strength (1, 2 and 3 kV/cm) during 60 s. Moreover, IPL was applied at various voltages (800, 1000, and 1200 V) for 60 s. The SWE was performed for 5 min at varying temperatures (110, 130, 150, 170, and 190 °C). The maximum yield of total catechin was 44.35 ± 2.00 mg/g dry green tea leaves at PEF treatment conditions of 2 kV/cm during 60 s, as well as the SWE temperature of 130 °C. In the case of IPL treatment, the largest amount of total catechin was 48.06 ± 5.03 mg/g dry green tea leaves at 800 V during 60 s when the extraction temperature was 130 °C. The total catechin content was increased by 15.43% for PEF and 25.09% for IPL compared to the value of untreated leaves. This study verified that PEF and IPL had a positive effect on the enhancement of tea catechins extraction from green tea leaves using SWE.

Curcumin Reduced H2O2- and G2385R-LRRK2-Induced Neurodegeneration

Mutations in leucine-rich repeat kinase 2 gene (LRRK2) are the most frequent genetic factors contributing to Parkinson's disease (PD). G2385R-LRRK2 increases the risk for PD susceptibility in the Chinese population. However, the pathological role of G2385R-LRRK2 is not clear. In this study, we investigate the roles of G2385R-LRRK2 in neurodegeneration underlying PD pathogenesis using cell biology and pharmacology approaches. We demonstrated that expression of G2385R-LRRK2-induced neurotoxicity in human neuroblastoma SH-SY5Y and mouse primary neurons. G2385R-LRRK2 increased mitochondrial ROS, activates caspase-3/7, and increased PARP cleavage, resulting in neurotoxicity. Treatment with curcumin (an antioxidant) significantly protected against G2385R-LRRK2-induced neurodegeneration by reducing mitochondrial ROS, caspase-3/7 activation, and PARP cleavage. We also found that the cellular environmental stressor, H₂O₂ significantly promotes both WT-LRRK2- and G2385R-LRRK2-induced neurotoxicity by increasing mitochondrial ROS, caspase-3/7 activation, and PARP cleavage, while curcumin attenuated this combined neurotoxicity. These findings not only provide a novel understanding of G2385R roles in neurodegeneration and environment interaction but also provide a pharmacological approach for intervention for G2385R-LRRK2-linked PD.

The pros and cons of drinking tea

Tea is the most frequently consumed beverage worldwide besides water. Generally, there are five most popular types of tea: green, white, black, Pu’er, and oolong. Tea possesses significant antioxidant, anti-inflammatory, antimicrobial, anticarcinogenic, antihypertensive, neuroprotective, and cholesterol-lowering properties. Several research investigations, epidemiological studies, and meta-analyses suggest that tea and its bioactive polyphenolic constituents have numerous beneficial effects on health, including the prevention of many diseases, such as cancer, diabetes, arthritis, cardiovascular disease, stroke, and obesity. Recently, there are many reports about the resistance of tea to COVID-19 virus on the Internet, which has attracted a lot of attention to tea drinking and the discussion about the pros and cons of tea drinking. Based on our research results and relevant reports form literatures, this review is intended to highlight the beneficial effects and possible side-effects associated with tea consumption, answer 10 questions and point out a few matters for attention.

Removal of polyethylene glycols from wastewater: A comparison of different approaches

Physicochemical methods such as adsorption on activated carbon, oxidation with either ozone or Fenton reagent, and chemical precipitation (coagulation), were assessed for the removal of polyethylene glycol (PEG) from wastewater. This contaminant is rarely investigated due to its low toxicity, although its presence limits the use of large water resources. The experimental tests showed that adsorption on activated carbon is well approximated by a Langmuir isotherm, and influenced by contact time, PEG molecular weight, pH, temperature, and initial PEG concentration. Ozonation allowed fragmenting the polymeric chains but was unable to remove completely the PEG, while about 85% of the total organic carbon (TOC) was removed by Fenton oxidation reaction by using a ratio between H₂O₂ and Fe^II close to 4. Coagulation did not produce results worthy of note, most likely because the uncharged PEG molecule does not interact with the iron hydroxide flocs. However, when performed after the Fenton oxidation (i.e., by simply raising the pH to values > 8), it allowed a further reduction of the residual TOC, up to 96% of the total, in the best case. Based on the resources used by each process studied and in consideration of the effectiveness of each of them, a semi-quantitative comparison on the sustainability of the different approaches is proposed.

Current Quest in Natural Bioactive Compounds for Alzheimer's Disease: Multi-Targeted-Designed-Ligand Based Approach with Preclinical and Clinical Based Evidence

Alzheimer's disease is a common and most chronic neurological disorder (NDs) associated with cognitive dysfunction. Pathologically, Alzheimer's disease (AD) is characterized by the presence of β-amyloid (Aβ) plaques, hyper-phosphorylated tau proteins, and neurofibrillary tangles, however, persistence oxidative-nitrative stress, endoplasmic reticulum stress, mitochondrial dysfunction, inflammatory cytokines, pro-apoptotic proteins along with altered neurotransmitters level are common etiological attributes in its pathogenesis. Rivastigmine, memantine, galantamine, and donepezil are FDA approved drugs for symptomatic management of AD, whereas tacrine has been withdrawn because of hepatotoxic profile. These approved drugs only exert symptomatic relief and exhibit poor patient compliance. In the current scenario, the number of published evidence shows the neuroprotective potential of naturally occurring bioactive molecules via their antioxidant, anti-inflammatory, antiapoptotic and neurotransmitter modulatory properties. Despite their potent therapeutic implications, concerns have arisen in context to their efficacy and probable clinical outcome. Thus, to overcome these glitches, many heterocyclic and cyclic hydrocarbon compounds inspired by natural sources have been synthesized and showed improved therapeutic activity. Computational studies (molecular docking) have been used to predict the binding affinity of these natural bioactive as well as synthetic compounds derived from natural sources for the acetylcholine esterase, α/β secretase Nuclear Factor kappa- light-chain-enhancer of activated B cells (NF-kB), Nuclear factor erythroid 2-related factor 2(Nrf2) and other neurological targets. Thus, in this review, we have discussed the molecular etiology of AD, focused on the pharmacotherapeutics of natural products, chemical and pharmacological aspects and multi-targeted designed ligands (MTDLs) of synthetic and semisynthetic molecules derived from the natural sources along with some important on-going clinical trials.

Neuroprotective Effect of Spice Oleoresins on Memory and Cognitive Impairment Associated with Scopolamine-Induced Alzheimer's Disease in Rats

Oleoresins are a mixture of volatile and nonvolatile components of concentrated forms of wholesome products. Even though there are several reports on the effect of spice or spice components on Alzheimer's disease, there are no studies on the effect of spice oleoresins. Hence, this study investigates the effect of pepper, chili, and turmeric oleoresins in Alzheimer's type of cognitive impairment in the rat model. The animals were grouped into six groups with six animals in each. They were (i) normal, (ii) scopolamine, (iii) scopolamine + pepper oleoresin, (iv) scopolamine + turmeric oleoresin, (v) scopolamine + chili oleoresin and (vi) scopolamine + donepezil for 13 days. Learning memory and acquisition memory were evaluated by a Morris water maze, and the locomotor activity was assessed by an actophotometer. Biochemical parameters such as AChE, malondialdehyde, reduced glutathione, glutathione peroxidase, superoxide dismutase, and catalase were studied. The brain histology was also studied. The scopolamine treatment significantly (P < 0.05) elevated the locomotor activity and escape latency time and reduced the time spent in the target quadrant, which was reversed in the case of the oleoresin treatment. Scopolamine-mediated changes in AChE, malondialdehyde, reduced glutathione, glutathione peroxidase, superoxide dismutase, and catalase were improved after the treatment with oleoresins. Among the three oleoresins, chili oleoresin were the most effective in behavioral activity, brain biomarkers, and recovery of antioxidant capacities when compared to the drug treatment. Chili and pepper oleoresins improved the protection against hippocampal damage. These oleoresins can be potent preventive/therapeutic agents against Alzheimer's disease. This study confirms the effect of spice oleoresins in Alzheimer's disease condition.

Anti-Oxidant in China: A Thirty-Year Journey

Anti-oxidant refers to such a kind of endogenous or exogenous compound that is able to retard or even prohibit in vivo or in vitro oxidation with only small amount being used. The study of anti-oxidants starts nearly 30 years ago, and the research on this topic in China almost begins simultaneously with that in the world. Gratifyingly, contributions on anti-oxidants from China researchers have rapidly increased in the recent decade as anti-oxidants have become a hot topic in biochemistry, pharmacology, food science, chemistry as well as other related disciplines. Anti-oxidants provide a specific viewpoint for clarifying pharmacological effects of Chinese medicinal herbs. For example, as a traditional Chinese medicinal herb, Panax ginseng C. A. Meyer is found to be a natural anti-oxidant resource. Meanwhile, some signaling pathways such as nuclear factor-[Formula: see text]B (NF-[Formula: see text]B), nuclear factor erythroid 2 related factor 2 (Nrf2), and Kelch-like ECH associated protein 1 (Keap1) are regarded to play an important role in anti-oxidant responses. These findings provide a substantial basis for understanding the pharmacological behaviors of Chinese medicinal herbs in view of regulating the aforementioned signaling pathways. Moreover, inhibition of reactive oxygen species (ROS) by supplementation of anti-oxidant becomes a popularly accepted idea in keeping health and treating diseases. Isolations of antio-xidative ingredients from medicinal herbs and foods lead to set up a large range of anti-oxidative compound libraries, and intake of anti-oxidants from foods may be the most efficient way for supplementing exogenous anti-oxidants. On the other hand, designing anti-oxidants with novel structures motivates organic and medicinal chemists to explore the structure–activity relationship, and then, to find novel structural features with anti-oxidative properties. Therefore, it is reasonable to believe that China researchers will donate more endeavors to obtain more achievements on anti-oxidants in the future.

Targeting photodynamic and photothermal therapy to the endoplasmic reticulum enhances immunogenic cancer cell death

Immunogenic cell death (ICD)-associated immunogenicity can be evoked through reactive oxygen species (ROS) produced via endoplasmic reticulum (ER) stress. In this study, we generate a double ER-targeting strategy to realize photodynamic therapy (PDT) photothermal therapy (PTT) immunotherapy. This nanosystem consists of ER-targeting pardaxin (FAL) peptides modified-, indocyanine green (ICG) conjugated- hollow gold nanospheres (FAL-ICG-HAuNS), together with an oxygen-delivering hemoglobin (Hb) liposome (FAL-Hb lipo), designed to reverse hypoxia. Compared with non-targeting nanosystems, the ER-targeting naosystem induces robust ER stress and calreticulin (CRT) exposure on the cell surface under near-infrared (NIR) light irradiation. CRT, a marker for ICD, acts as an ‘eat me’ signal to stimulate the antigen presenting function of dendritic cells. As a result, a series of immunological responses are activated, including CD8⁺ T cell proliferation and cytotoxic cytokine secretion. In conclusion, ER-targeting PDT-PTT promoted ICD-associated immunotherapy through direct ROS-based ER stress and exhibited enhanced anti-tumour efficacy.

Reactive oxygen species induced by endoplasmic reitculum stress can be exploited for cancer therapy. Here, nanoparticles are targetted to the endoplasmic reticulum and, when accompanied by PDT, produce stress resulting in calreticulin exposure on the cell surface, which activates dendritic cells.

Targeting Inflammatory Pathways in Alzheimer's Disease: A Focus on Natural Products and Phytomedicines

Studies of the brains of Alzheimer's disease (AD) patients have revealed key neuropathological features, such as the deposition of aggregates of insoluble amyloid-β (Aβ) peptides and neurofibrillary tangles (NFTs). These pathological protein deposits, including Aβ peptides (which form senile plaques) and hyperphosphorylated tau (which aggregates into NFTs), have been assumed to be 'the cause of AD'. Aβ has been extensively targeted to develop an effective disease-modifying therapy, but with limited clinical success. Emerging therapies are also now targeting further pathological processes in AD, including neuroinflammation. This review focuses on the inflammatory and oxidative stress-related changes that occur in AD, and discusses some emerging anti-inflammatory natural products and phytomedicines. Many of the promising compounds are cytokine-suppressive anti-inflammatory drugs (CSAIDs), which target the proinflammatory AP1 and nuclear factor-κB signalling pathways and inhibit the expression of many proinflammatory cytokines, such as interleukin (IL)-1, IL-6, tumour necrosis factor-α, or nitric oxide produced by inducible nitric oxide synthase. However, many of these phytomedicines have not been tested in rigorous clinical trials in AD patients. It is not yet clear if the active compounds reach an effective concentration in the brain (due to limited bioavailability) or if they can slow down AD progression in long-term trials. The authors suggest that it is crucial for both the pharmacological and complementary medicine industries to conduct and fund those studies to significantly advance the field.

Synthesis of Non-Symmetrical Nitrogen-Containing Curcuminoids in the Pursuit of New Anticancer Candidates

Curcumin is known to display pronounced anticancer effects and a variety of other biological activities. However, the low bioavailability and fast metabolism of this molecule present an issue of concern with respect to its medicinal applications. To address this issue, structural modifications of the curcumin scaffold can be envisioned as a strategy to improve both the solubility and stability of this chemical entity, without compromising its biological activities. Previous work in our group targeted the synthesis of symmetrical azaheteroaromatic curcuminoids, which showed better solubility and cytotoxicity profiles compared to curcumin. In continuation of that work, we now focused on the synthesis of non-symmetrical nitrogen-containing curcuminoids bearing both a phenolic and an azaheteroaromatic moiety. In that way, we aimed to combine good solubility, antioxidant potential and cytotoxic properties into one molecule. Some derivatives were selected for further chemical modification of their rather labile β-diketone scaffold to the corresponding pyrazole moiety. In this way, thirteen new non-symmetrical aza-aromatic curcuminoids and four pyrazole-based analogues were successfully synthesized in a yield of 11-69 %. All newly synthesized analogues were evaluated for their antioxidant properties, reactive oxygen species (ROS) production, water solubility and anticancer activities. Several novel derivatives displayed good cytotoxicity profiles compared to curcumin, in combination with an improved water solubility and stability, and were thus identified as potential hit scaffolds for further optimization studies.

Dose-response assessment of chemically modified curcumin in experimental periodontitis

BACKGROUND

CMC2.24, a novel tri-ketonic chemically modified compound based on natural di-ketonic curcumin, has been shown to reduce bone loss and inflammatory mediators in experimental periodontitis, however, a potential dose-response relationship was not determined. The purpose of this study was to assess the effects of different doses of CMC2.24 on inflammation and bone resorption in vivo and also to describe on the effects of CMC2.24 on macrophage response.

METHODS

CMC2.24 was administered daily to animals for 28 days by oral gavage, at the following doses: 0 (control), 1, 3, 10, and 30 mg/kg of body weight. Experimental periodontitis was induced by injections of lipopolysaccharide (LPS) into the gingival tissues. Outcomes assessed were bone resorption, detection of tartrate-resistant acid phosphatase, and determination of gene expression. In vitro, macrophages (RAW264.7) were treated with different concentrations of CMC2.24: 1, 3, 10, and 30 μM and then subjected to different activation stimuli. Gene expression, phagocytic activity, production of reactive oxygen species (ROS) and cytokine production were evaluated.

RESULTS

CMC2.24 inhibited bone resorption, osteoclastogenesis, and tumor necrosis factor (TNF)-α expression in vivo. These beneficial responses reached maximum levels at a dose of 1 mg/kg, i.e. no dose-dependent effect. In vitro, CMC2.24 reduced the production of TNF-α and interleukin-10, inhibited phagocytic activity and stimulated production of ROS. A dose-dependent effect was observed only for ROS production.

CONCLUSION

Low doses of CMC2.24 (1 mg/kg/day) administered orally were sufficient to significantly inhibit alveolar bone resorption associated with the experimental periodontal disease; whereas in vitro macrophage inflammatory gene expression and phagocytosis were reduced, whereas production of ROS was stimulated.

Metabolomics of Green-Tea Catechins on Vascular-Endothelial-Growth-Factor-Stimulated Human-Endothelial-Cell Survival

Neovascularization causes serious oculopathy related to upregulation of vascular-endothelial-growth factor (VEGF) causing new capillary growth via endothelial cells. Green-tea-extract (GTE) constituents possess antiangiogenesis properties. We used VEGF to induce human umbilical-vein endothelial cells (HUVECs) and applied GTE, epigallocatechin gallate (EGCG), and mixtures of different compositions of purified catechins (M1 and M2) to evaluate their efficacies of inhibition and their underlying mechanisms using cell-cycle analysis and untargeted metabolomics techniques. GTE, EGCG, M1, and M2 induced HUVEC apoptosis by 22.1 ± 2, 20.0 ± 0.7, 50.7 ± 8.5, and 69.8 ± 4.1%, respectively. GTE exerted a broad, balanced metabolomics spectrum, involving suppression of the biosynthesis of cellular building blocks and oxidative-phosphorylation metabolites as well as promotion of the biosynthesis of membrane lipids and growth factors. M2 mainly induced mechanisms associated with energy and biosynthesis suppression. Therefore, GTE exerted mechanisms involving both promotion and suppression activities, whereas purified catechins induced extensive apoptosis. GTE could be a more promising antineovascularization remedy for ocular treatment.

Prevention of Lipid Peroxidation-derived Cyclic DNA Adduct and Mutation in High-Fat Diet-induced Hepatocarcinogenesis by Theaphenon E

Obesity is associated with cancer risk and its link with liver cancer is particularly strong. Obesity causes non-alcoholic fatty liver disease (NAFLD) that could progress to hepatocellular carcinoma (HCC). Chronic inflammation likely plays a key role. We carried out a bioassay in the high-fat diet (HFD)-fed C57BL/6J mice to provide insight into the mechanisms of obesity-related HCC by studying γ-OHPdG, a mutagenic DNA adduct derived from lipid peroxidation. In an 80-week bioassay, mice received a low-fat diet (LFD), high-fat diet (HFD), and HFD with 2% Theaphenon E (TE) (HFD+TE). HFD mice developed a 42% incidence of HCC and LFD mice a 16%. Remarkably, TE, a standardized green tea extract formulation, completely blocked HCC in HFD mice with a 0% incidence. γ-OHPdG measured in the hepatic DNA of mice fed HFD and HFD+TE showed its levels increased during the early stages of NAFLD in HFD mice and the increases were significantly suppressed by TE, correlating with the tumor data. Whole-exome sequencing showed an increased mutation load in the liver tumors of HFD mice with G>A and G>T as the predominant mutations, consistent with the report that γ-OHPdG induces G>A and G>T. Furthermore, the mutation loads were significantly reduced in HFD+TE mice, particularly G>T, the most common mutation in human HCC. These results demonstrate in a relevant model of obesity-induced HCC that γ-OHPdG formation during fatty liver disease may be an initiating event for accumulated mutations that leads to HCC and this process can be effectively inhibited by TE. Cancer Prev Res; 11(10); 665-76. ©2018 AACR.

Antioxidant Activities of Phenolic Metabolites from Flemingia philippinensis Merr. et Rolfe and Their Application to DNA Damage Protection

F. philippinensis Merr. et Rolfe has been cultivated on a large scale and is widely consumed by local inhabitants as an important nutraceutical, especially against rheumatism which has a deep connection with antioxidants. In this study, a total of 18 different phenolic metabolite compounds in F. philippinensis were isolated and identified, and evaluated for their antioxidant and DNA damage protection potential. The antioxidant activity of the 18 identified compounds was screened using DPPH, ORAC, hydroxyl and superoxide radical scavenging assays. The antioxidant potential of the compounds was found to differ by functionality and skeleton. However, most compounds showed a good antioxidant potential. In particular, seven of the identified compounds, namely, compounds 2, 3, 6, 10, 11, 15 and 16, showed significant protective effects on pBR322 plasmid DNA against the mutagenic and toxic effects of Fenton’s reaction. The most active compound, compound 2, displayed a dose-dependent DNA damage protection potential in the range of 7.5~60.0 μM. The DNA damage protective effect of the identified compounds was significantly correlated with the hydroxyl radical scavenging activity. Compounds that exhibited effective (IC₅₀ = 5.4~12.5 μg/mL) hydroxyl radical scavenging activity were found to be the ones with higher DNA damage protection potential.

Hypersensitivity of BRCA2 deficient cells to rosemary extract explained by weak PARP inhibitory activity

Rosemary extract is used in food additives and traditional medicine and has been observed to contain anti-tumor activity. In this study, rosemary extract is hypothesized to induce synthetic lethality in BRCA2 deficient cells by PARP inhibition. Chinese hamster lung V79 cells and its mutant cell lines, V-C8 (BRCA2 deficient) and V-C8 with BRCA2 gene correction were used. Rosemary extract and its major constituent chemicals were tested for their cytotoxicity by colony formation assay in cells of different BRCA2 status. The latter chemicals were tested for inhibitory effect of poly (ADP-ribose) polymerase (PARP) activity in vitro and in vivo. Rosemary has shown selective cytotoxicity against V-C8 cells (IC50 17 µg/ml) compared to V79 cells (IC50 26 µg/ml). Among tested chemicals, gallic acid and carnosic acid showed selective cytotoxicity to V-C8 cells along with PARP inhibitory effects. Carnosol showed comparative PARP inhibitory effects at 100 µM compared to carnosic acid and gallic acid, but the selective cytotoxicity was not observed. In conclusion, we predict that within rosemary extract two specific constituent components; gallic acid and carnosic acid were the cause for the synthetic lethality.

Protective role of epigallocatechin-3-gallate on arsenic induced testicular toxicity in Swiss albino mice

Arsenic, often referred to as the king of poisons is carcinogenic in humans and animals. It affects multiorgan systems including reproduction. The present study was undertaken to explore the protective role of green tea compound, epigallocatechin-3-gallate (EGCG) on arsenic induced testicular toxicity in Swiss albino mice. Thirty two adult male mice were randomly assigned to four groups (n=8). Group I served as control without test chemical. The group II received arsenic (200ppm) through drinking water, group III received only EGCG (20mg/kgb.wt., intraperitoneally, alternate days) and group IV was administered arsenic+EGCG for 40days. Factorial experimental design was employed to assess the treatment effect. The EGCG restored arsenic induced decrements in epididymal sperm concentration, kinematic attributes (total motility, rapid, progressive motile, fast progressive, VSL, VAP, VCL, BCF, LIN, WOB, STR and Type A), structutal membrane integrity, functional membrane integrity and mitochondrial membrane potential. As evidenced by the histoarchitectural studies, the EGCG reversed the deleterious effects of arsenic on testicular malondialdehyde (p<0.05) levels, reduced glutathione, antioxidative enzymes and spermatogenesis. Overall, the results suggest that EGCG reduces the testicular oxidative stress induced by arsenic poisoning and thereby protect the reproductive system.

Bridging Type 2 Diabetes and Alzheimer's Disease: Assembling the Puzzle Pieces in the Quest for the Molecules With Therapeutic and Preventive Potential

Type 2 diabetes (T2D) and Alzheimer's disease (AD) are two age-related amyloid diseases that affect millions of people worldwide. Broadly supported by epidemiological data, the higher incidence of AD among type 2 diabetic patients led to the recognition of T2D as a tangible risk factor for the development of AD. Indeed, there is now growing evidence on brain structural and functional abnormalities arising from brain insulin resistance and deficiency, ultimately highlighting the need for new approaches capable of preventing the development of AD in type 2 diabetic patients. This review provides an update on overlapping pathophysiological mechanisms and pathways in T2D and AD, such as amyloidogenic events, oxidative stress, endothelial dysfunction, aberrant enzymatic activity, and even shared genetic background. These events will be presented as puzzle pieces put together, thus establishing potential therapeutic targets for drug discovery and development against T2D and diabetes-induced cognitive decline-a heavyweight contributor to the increasing incidence of dementia in developed countries. Hoping to pave the way in this direction, we will present some of the most promising and well-studied drug leads with potential against both pathologies, including their respective bioactivity reports, mechanisms of action, and structure-activity relationships.

Curcumin, A Potential Therapeutic Candidate for Anterior Segment Eye Diseases: A Review

Curcumin, the major curcuminoid of the turmeric, has been extensively used in many countries since ancient time for preventing and/or treating a multitude of diseases. This review is to illustrate the researches on the properties of curcumin and its potential therapeutic efficacy in major anterior segment eye diseases. The bio-medical potential of curcumin is restricted because of its low solubility and digestive bioavailability. This review will discuss promising research in improving curcumin bioavailability through structural modification. In vitro and in vivo research made progress in studying the beneficial effects of curcumin on major anterior segment eye diseases, including anti-angiogenesis effect in corneal diseases; anti-inflammation or anti-allergy effects in dry eye disease, conjunctivitis, anterior uveitis; anti-proliferation and pro-apoptosis effects in pterygium; anti-oxidative stress, anti-osmotic stress, anti-lipid peroxidation, pro-apoptosis, regulating calcium homeostasis, sequestrating free radicals, protein modification and degradation effects in cataracts; neuroprotective effects in glaucoma. Curcumin exhibited to be a potent therapeutic candidate for treating those anterior segment eye diseases.

A gradient based facile HPLC method for simultaneous estimation of antioxidants extracted from tea powder

A new simple, rapid and precise RP-HPLC method was developed for the extraction and quantitative estimation of caffeine (C), (-)-epigallocatechin gallate (EGCG), (+)-catechin(Ct), (-)-epicatechin(EC), and (-)-epicatechin gallate (ECG) (collectively named as Tea Powder Bioactives TPBAs) extracted from tea powder using different ratios of ethanol: water. The simultaneous determination of TPBAs was performed using the UV spectrophotometric method which employs the absorbance at 205 nm (λmax of caffeine and polyphenols). This method is a gradient based HPLC method with a flow rate of 0.8 mL/min using Inertsil ODS 100 × 4.6 mm, 3 μm column with methanol and ammonium dihydrogen phosphate (pH-2.8) as mobile phase. The method was validated in terms of specificity, precision, linearity, accuracy, limit of quantification (LOQ), and limit of detection (LOD). The linearity of the proposed method was investigated for concentration ranging between 0.5-60 μg/mL with regression co-efficient, R(2) = 0.999-1.0. This method estimates all the TPBAs simultaneously with enhanced precision and linearity as per the ICH guidelines. Also, to confirm the individual TPBA, the antioxidant property of the each TPBA was analyzed which was commensurate with that of the previous reports.

Antioxidant Activity/Capacity Measurement. 3. Reactive Oxygen and Nitrogen Species (ROS/RNS) Scavenging Assays, Oxidative Stress Biomarkers, and Chromatographic/Chemometric Assays

There are many studies in which the antioxidant potential of different foods have been analyzed. However, there are still conflicting results and lack of information as a result of unstandardized assay techniques and differences between the principles of the methods applied. The measurement of antioxidant activity, especially in the case of mixtures, multifunctional or complex multiphase systems, cannot be evaluated satisfactorily using a simple antioxidant test due to the many variables influencing the results. In the literature, there are many antioxidant assays that are used to measure the total antioxidant activity/capacity of food materials. In this review, reactive oxygen and nitrogen species (ROS/RNS) scavenging assays are evaluated with respect to their mechanism, advantages, disadvantages, and potential use in food systems. On the other hand, in vivo antioxidant activity (AOA) assays including oxidative stress biomarkers and cellular-based assays are covered within the scope of this review. Finally, chromatographic and chemometric assays are reviewed, focusing on their benefits especially with respect to their time saving, cost-effective, and sensitive nature.

Examining the potential clinical value of curcumin in the prevention and diagnosis of Alzheimer’s disease

Curcumin derived from turmeric is well documented for its anti-carcinogenic, antioxidant and anti-inflammatory properties. Recent studies show that curcumin also possesses neuroprotective and cognitive-enhancing properties that may help delay or prevent neurodegenerative diseases, including Alzheimer’s disease (AD). Currently, clinical diagnosis of AD is onerous, and it is primarily based on the exclusion of other causes of dementia. In addition, phase III clinical trials of potential treatments have mostly failed, leaving disease-modifying interventions elusive. AD can be characterised neuropathologically by the deposition of extracellular β amyloid (Aβ) plaques and intracellular accumulation of tau-containing neurofibrillary tangles. Disruptions in Aβ metabolism/clearance contribute to AD pathogenesis. In vitro studies have shown that Aβ metabolism is altered by curcumin, and animal studies report that curcumin may influence brain function and the development of dementia, because of its antioxidant and anti-inflammatory properties, as well as its ability to influence Aβ metabolism. However, clinical studies of curcumin have revealed limited effects to date, most likely because of curcumin’s relatively low solubility and bioavailability, and because of selection of cohorts with diagnosed AD, in whom there is already major neuropathology. However, the fresh approach of targeting early AD pathology (by treating healthy, pre-clinical and mild cognitive impairment-stage cohorts) combined with new curcumin formulations that increase bioavailability is renewing optimism concerning curcumin-based therapy. The aim of this paper is to review the current evidence supporting an association between curcumin and modulation of AD pathology, including in vitro and in vivo studies. We also review the use of curcumin in emerging retinal imaging technology, as a fluorochrome for AD diagnostics.

Metabogenic and Nutriceutical Approaches to Address Energy Dysregulation and Skeletal Muscle Wasting in Duchenne Muscular Dystrophy

Duchenne Muscular Dystrophy (DMD) is a fatal genetic muscle wasting disease with no current cure. A prominent, yet poorly treated feature of dystrophic muscle is the dysregulation of energy homeostasis which may be associated with intrinsic defects in key energy systems and promote muscle wasting. As such, supplementative nutriceuticals that target and augment the bioenergetical expansion of the metabolic pathways involved in cellular energy production have been widely investigated for their therapeutic efficacy in the treatment of DMD. We describe the metabolic nuances of dystrophin-deficient skeletal muscle and review the potential of various metabogenic and nutriceutical compounds to ameliorate the pathological and clinical progression of the disease.

Role of Green Tea in Reducing Epidermal Thickness upon Ultraviolet Light-B Injury in BALB/c Mice

The main environmental source for skin damage is ultraviolet (UV) radiation. Many adverse effects have been recognized as the result of prolonged cutaneous exposure to solar ultraviolet radiation, such as erythema, edema, apoptosis, hyperplastic responses, photo-aging, and skin cancer development. Green tea provides photo-protection against UV radiation through many mechanisms including anti-inflammatory, immunomodulatory, and antioxidant properties. The aim of this study was to evaluate the effect of green tea in reducing epidermal thickness on mouse’s skin exposed to UVB irradiation. Thirty mice (Mus musculus species, BALB/c strain) underwent this study and were divided into 3 groups: control group (n=10 mice), without UVB exposure and green tea administration; exposure group (n=10 mice), which were exposed to UVB light only; and treatment group (n=10 mice), which were exposed to UVB light and treated with 1 mL of green tea through oral gavage. Mice from both groups (exposure and treatment) were subjected to UVB irradiation 4 days/week (20 minutes/day, 4 weeks). It concluded that oral administration of green tea was provided photo-protection against UVB induced hyperplasia; therefore, it can be regarded as a natural alternative for photo-protection.

Oxidative stress and cancer; the role of hesperidin, a citrus natural bioflavonoid, as a cancer chemoprotective agent

Cancer is the third cause of death worldwide, with complex etiology, and is defined as an uncontrolled growth of cells. A high proportion of cancer incidence and deaths are due to different environmental and genetic factors such as high body mass index, low fruit and vegetable intake, lack of physical activity, tobacco use, alcohol consumption, exposure to radiation, chronic infections, and heredity also. In addition, oxidative stress plays a crucial role in the pathophysiology of different types of cancer. Hence, screening and testing of more effective compounds with minimum side effects for the prevention and treatment of cancers started a few decades ago. Regarding this, much attention has been paid to natural antioxidants as a novel prevention and treatment strategy for cancer. Flavonoids are one of the most important ingredients in vegetables and fruits, especially in the genus Citrus. Hesperidin is a flavonone glycoside, belonging to the flavonoid family, which is widely found in Citrus species and acts as a potent antioxidant and anticancer agent. In the present review, we attempt to provide an overview and summarize the scientific literature about the cancer chemoprotective effects of hesperidin with an emphasis on its relation to the protection roles against oxidative stress.

Synthesis of novel steroidal curcumin derivatives as anti-Alzheimer's disease candidates: Evidences-based on in vivo study

Alzheimer's disease (AD) is a complex disease in which a single monofunctional 'targeted' drug is uneffective for management. Hybrid drugs that impact multiple targets simultaneously are better at controlling such complex disease systems. Hybrid agents were synthesized through the combination of the steroid moiety with curcumin molecule. Also novel curcumin analogues containing promising heterocyclic nucleus fused to the essential pharmacophoric feature of the curcumin moiety, were synthesized. The aim of the present study was extended to elucidate the efficacy of these novel synthesized compounds in the regression of AD induced in adult female albino rats. The results revealed that treatment of AD groups with compounds 3, 5, 8c or rivastigmin experienced significant increase in brain Ach, GSH, paraoxenase and BCL2 levels with respect to untreated group associated with significant decrease in brain AchE activity, urinary 8-OHG level, serum Caspase-3 level and brain P53 level relative to the untreated group. Immunohistochemical investigation revealed that the selected treatments caused marked increase in ChAT positive cells. These findings were documented by the histological investigation of the brain tissue. The activity of tested compounds showed gradual increase from compound b followed by compound 8c then compound 5. The anti-cholinesterase potential, anti-oxidant properties and anti-apoptotic activity are responsible for the anti-Alzheimer's disease potential of these compounds.

Effects of an antioxidant beverage on biomarkers of oxidative stress in Alzheimer's patients

PURPOSE

The purpose of the study was to test whether daily consumption of a beverage with high antioxidant power, combining extracts of green tea and apple over a period of 8 months, would affect blood and urinary concentrations of biomarkers of oxidative stress in Alzheimer's patients.

METHODS

The study included 100 subjects, 48 of them were Alzheimer's patients, aged 76.5 ± 3.5 years, and 52 were control subjects, aged 79 ± 4 years, without dementia. Three blood and urine samples were taken from each participant, the first (T i) before starting the antioxidant or placebo beverage intake, the second (T m) 4 months after the antioxidant or placebo beverage intake and the third (T f) 8 months after the antioxidant or placebo beverage intake, and concentrations of biomarkers of oxidative stress were measured on serum, lysed erythrocytes or urine by UV-Vis spectrophotometry or by competitive in vitro enzyme-linked immunosorbent assay, according to the parameter analyzed.

RESULTS

The administration of the antioxidant beverage to the Alzheimer's patients prevented the decrease in total antioxidant status in the moderate phase of the disease (T i = 1.40 ± 0.10 mmol/L vs T f = 1.20 ± 0.08 mmol/L), increased values of glutathione peroxidase and superoxide dismutase in initial (165 and 24 % respectively) and moderate phase (75 and 85 % respectively), and prevented the increase in protein carbonyls in moderate phase (T i = 0.17 ± 0.07 nmol/mg protein vs T f = 0.21 ± 0.06 nmol/mg protein), with a significant decrease in protein carbonyls since the fourth month of the intake in initial phase (T m = 0.21 ± 0.06 nmol/mg protein vs T f = 0.11 ± 0.05 nmol/mg protein).

CONCLUSION

Our results suggest that antioxidant beverage could be used as a natural complementary therapy for alleviate or decrease the oxidative stress effects in the stages of Alzheimer's disease.

The photochemistry of carbon nanotubes and its impact on the photo-degradation of dye pollutants in aqueous solutions

It is reported that carbon nanotubes (CNTs) could either generate reactive oxygen species (ROS) under light irradiation or serve as high-efficient scavenger for ROS. However, it is unclear which role predominates as CNTs enter into aquatic environment. To answer this question, a systematic study of the photochemistry of a pristine and a surface-functionalized CNTs in aqueous suspensions was investigated with both time-resolved and steady state analytical approaches. The transient absorption spectra demonstrate that CNTs could be photo-ionized and trap hydrated electrons upon high energy irradiation. In steady state UV irradiation, CNTs could promote the generation of ROS, such as (1)O2 and OH. However, in the presence of H2O2, the OH scavenging effect predominated in the aqueous suspensions of CNTs. The presence of CNTs suppressed the photo-degradation of dye pollutants, as an integrated result of inner filter effect, adsorption effect, and ROS generation and scavenging effect. The results provide useful information for the understanding of the environmental implications of CNTs.

Role of dietary and endogenous antioxidants in diabetes

Diabetes affects different people of all ages, race, and sex. This is a condition characterized by a state of chronic hyperglycaemia that leads to an increase of intracellular oxidative stress linked to the overproduction of free radicals. In the present review, we focus our attention on the molecular mechanisms leading to oxidative stress-mediates complications with particular regard to central nervous system (CNS). Furthermore, the present review reports the effects of different kind of antioxidants with enzymatic and nonenzymatic action that may significantly decrease the intracellular free radicals' overproduction and prevents the hyperglycaemia-mediated complications.

Effect of tea polyphenols on lipid peroxidation and antioxidant activity of litchi (Litchi chinensis Sonn.) fruit during cold storage

To understand the potential of application of tea polyphenols to the shelf life extension and quality maintenance of litchi (Litchi chinensis Sonn.) fruit, the fruits were dipped into a solution of 1% tea phenols for 5 min before cold storage at 4 °C. Changes in browning index, contents of anthocyanins and phenolic compounds, superoxide dismutase (SOD) and peroxidase (POD) activities, O₂^.− production rate and H₂O₂ content, levels of relative leakage rate and lipid peroxidation, and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity were measured after 0, 10, 20 and 30 days of cold storage. The results showed that application of tea polyphenols markedly delayed pericarp browning, alleviated the decreases in contents of total soluble solids (TSS) and ascorbic acid, and maintained relatively high levels of total phenolics and anthocyanins of litchi fruit after 30 days of cold storage. Meanwhile, the treatment reduced the increases in relative leakage rate and lipid peroxidation content, delayed the increases in both O₂^.− production rate and H₂O₂ contents, and increased SOD activity but reduced POD activity throughout this storage period. These data indicated that the delayed pericarp browning of litchi fruit by the treatment with tea polyphenols could be due to enhanced antioxidant capability, reduced accumulations of reactive oxygen species and lipid peroxidation, and improved membrane integrity.

High-throughput superoxide anion radical scavenging capacity assay

A high-throughput superoxide anion radical (O2(•-)) scavenging capacity assay based on the xanthine oxidase/xanthine reaction system was developed and validated in the present study. The reaction conditions including detection wavelength, concentrations of reactant components, reaction temperature, reaction time, pH, terminator reagent, and sample dissolving solvents were optimized. The accuracy and reliability of the assay were assessed by evaluation of linearity (r(2) = 0 .9513-0.9957), precision (intraday RSD 1.13-4.05% and interday RSD 2.13-5.62%), accuracy (95.64-97.42% recovery), and stability (RSD 2.62-6.19%), as well as comparison with the conventional colorimetric method. The EC50 values obtained by the current method and the conventional assay were highly correlated (r > 0.99). This high-throughput O2(•-) scavenging assay may be used for screening and estimating potential superoxide anion radical (O2(•-)) scavengers, especially food extracts and natural products with a very small amount of test material.

Cocoa powder triggers neuroprotective and preventive effects in a human Alzheimer's disease model by modulating BDNF signaling pathway

The molecular mechanisms linking Aβ to the onset of neurotoxicity are still largely unknown, but several lines of evidence point to reactive oxygen species, which are produced even under the effect of nanomolar concentrations of soluble Aβ-oligomers. The consequent oxidative stress is considered as the mediator of a cascade of degenerative events in many neurological disorders. Epidemiological studies indicate that dietary habits and antioxidants from diet can influence the incidence of neurodegenerative disorders such as Alzheimer's and Parkinson's diseases. In the recent years, a number of reviews have reported on neuroprotective effects of polyphenols in cell and animal models. However, the majority of these studies have focused only on the anti-oxidant properties of these compounds and less on the mechanism/s of action at cellular level. In this work we investigated the effect of cocoa polyphenolic extract on a human AD in vitro model. The results obtained, other than confirming the anti-oxidant properties of cocoa, demonstrate that cocoa polyphenols triggers neuroprotection by activating BDNF survival pathway, both on Aβ plaque treated cells and on Aβ oligomers treated cells, resulting in the counteraction of neurite dystrophy. On the light of the results obtained the use of cocoa powder as preventive agent for neurodegeneration is further supported.

Healthy aging diets other than the Mediterranean: a focus on the Okinawan diet

The traditional diet in Okinawa is anchored by root vegetables (principally sweet potatoes), green and yellow vegetables, soybean-based foods, and medicinal plants. Marine foods, lean meats, fruit, medicinal garnishes and spices, tea, alcohol are also moderately consumed. Many characteristics of the traditional Okinawan diet are shared with other healthy dietary patterns, including the traditional Mediterranean diet, DASH diet, and Portfolio diet. All these dietary patterns are associated with reduced risk for cardiovascular disease, among other age-associated diseases. Overall, the important shared features of these healthy dietary patterns include: high intake of unrefined carbohydrates, moderate protein intake with emphasis on vegetables/legumes, fish, and lean meats as sources, and a healthy fat profile (higher in mono/polyunsaturated fats, lower in saturated fat; rich in omega-3). The healthy fat intake is likely one mechanism for reducing inflammation, optimizing cholesterol, and other risk factors. Additionally, the lower caloric density of plant-rich diets results in lower caloric intake with concomitant high intake of phytonutrients and antioxidants. Other shared features include low glycemic load, less inflammation and oxidative stress, and potential modulation of aging-related biological pathways. This may reduce risk for chronic age-associated diseases and promote healthy aging and longevity.

Synthesis and characterization of new curcumin derivatives as potential chemotherapeutic and antioxidant agents

The purpose of this work was to synthesize a series of symmetrical analogs (CA2-CA7) of curcumin and determine their efficacy as antioxidant and anticancer agents in vitro. The six analogs were successfully synthesized and characterized, one of which, CA6, had not been previously reported in the literature. With the exception of CA2, the analogs had lower predicted aqueous solubilities and higher partition coefficients than curcumin. Two analogs, CA2 and CA3, had lower potencies as anticancer agents compared with curcumin, while CA6 had a slightly higher IC50 value. Two different trends in the antioxidant capabilities of curcumin and its analogs were determined when assessed in vitro or in cell culture. The in vitro DPPH assay clearly showed curcumin as the strongest antioxidant as compared with the analogs when tested at the same concentration or at their IC50 value. The cell culture-based reactive oxygen species/reactive nitrogen species assay indicated that CA3 and CA6 were equal to curcumin in their free radical scavenging ability at the same concentration, but when curcumin and its analogs were tested at their respective IC50 values, CA4 and CA5 showed excellent antioxidant capacities. These results indicate that in cell culture, the ability of these analogs to produce antioxidant effects may be tied to their downstream effects.

Green tea catechins prevent obesity through modulation of peroxisome proliferator-activated receptors

Epidemiological evidence and experimental studies suggest that drinking green tea is associated with a lower risk of obesity and related diseases. However, the mechanisms of these effects are not clear. In the present study, we investigated the anti-obesity mechanisms of green tea catechins (GTCs) through modulation of peroxisome proliferator activated-receptor (PPAR) pathways in high-fat diet-induced obesity in rats. GTC supplementation significantly attenuated the increased body and liver weights and the elevated serum and liver triglyceride levels. Meanwhile, GTCs increased the PPARγ levels in subcutaneous white adipose tissue (SWAT) and decreased the PPARγ levels in visceral white adipose tissue (VWAT). In addition, GTC treatment up-regulated the levels of PPARδ in SWAT, VWAT, and brown adipose tissue and increased the expression of genes involved in fatty acid oxidation in brown adipose tissue. Our results suggest that GTCs exert their anti-obesity mechanism in part by modulating PPAR signaling pathways.

Effects of turmeric on Alzheimer's disease with behavioral and psychological symptoms of dementia

We describe here three patients with the Alzheimer's Disease (AD) whose behavioral symptoms were improved remarkably as a result of the turmeric treatment, which is the traditional Indian medicine. Their cognitive decline and Behavioral and Psychological Symptoms of Dementia (BPSD) were very severe. All three patients exhibited irritability, agitation, anxiety, and apathy, two patients suffer from urinary incontinence and wonderings. They were prescribed turmeric powder capsules and started recovering from these symptoms without any adverse reaction in the clinical symptom and laboratory data. After 12 weeks of the treatment, total score of the Neuro-Psychiatric Inventory-brief questionnaire decreased significantly in both acuity of symptoms and burden of caregivers. In one case, the Mini-Mental State Examination (MMSE) score was up five points, from 12/30 to 17/30. In the other two cases, no significant change was seen in the MMSE; however, they came to recognize their family within 1 year treatment. All cases have been taking turmeric for more than 1 year, re-exacerbation of BPSD was not seen. The present cases suggest a significant improvement of the behavioral symptoms in the AD with the turmeric treatment, leading to probable benefit of the use of turmeric in individuals with the AD with BPSD.

Curcumin and piperine abrogate lipid and protein oxidation induced by D-galactose in rat brain

Cerebellar atrophy during ageing can produce neurobehavioural changes characterized by cognitive and motor impairment. Chronic exposure to D-galactose, a reducing sugar can accelerate ageing by producing an unprecedented rise in oxidative load. This can enhance neuronal damage by promoting the oxidation of protein and lipids. We perceived that the simultaneous administration of piperine and curcumin, two powerful antioxidants can exert neuroprotective effect by inhibiting damage caused by the chronic exposure to D-galactose. Young Wistar rats treated with D-galactose (150 mg/kg, s.c.) were simultaneously treated with piperine alone, curcumin separately; and in combination for a period of 56 days by the oral route. A vehicle control, D-galactose alone and naturally aged control were also evaluated. Cognitive changes, motor impairment, protein carbonyls, protein thiols, advanced oxidation protein products, 4 hydroxynonenol and nitric oxide levels were determined in the brain homogenate. In order to ascertain the impact of cerebellum on motor performance, histopathological changes in the cerebellum were also established. Results obtained from our studies reflect a marked improvement in memory, sensorimotor performance, reduced oxidative and nitrosative burden on simultaneous treatment with piperine and curcumin. Furthermore, alterations produced in the Purkinje cells were minimized on treatment with the combination. Our studies demonstrated the influence of protein and lipid oxidation products on behavioural changes in D-galactose induced ageing model. Incorporation of these antioxidants might reduce the risk of developing neurodegenerative disorders, an important counterpart of advancing age.

Development of a validated UPLC-qTOF-MS Method for the determination of curcuminoids and their pharmacokinetic study in mice

Background

A specific and sensitive UPLC-qTOF-MS/MS method has been developed for the simultaneous determination of curcuminoids. These Curcuminoids comprises of curcumin, a principal curcuminoid and other two namely, demethoxycurcumin, and bisdemethoxycurcumin obtained from rhizomes of Curcuma longa an ancient Indian curry spice turmeric, family (Zingiberaceae).

Methods

These analytes were separated on a reverse phase C18 column by using a mobile phase of acetonitrile: 5% acetonitrile in water with 0.07% acetic acid (75:25 v/v), flow rate of 100 μL/min was maintained. The qTOF-MS was operated under multiple reaction monitoring (MRM) mode using electro-spray ionization (ESI) technique with positive ion polarity. The major product ions in the positive mode for curcuminoids were at m/z 369.1066, 339.1023 and 309.0214 respectively. The recovery of the analytes from mouse plasma was optimized using solid phase extraction technique.

Results

The total run time was 5 min and the peaks of the compounds, bisdemethoxycurcumin, demethoxycurcumin and curcumin occurred at 2.06, 2.23 and 2.40 min respectively. The calibration curves of bisdemethoxycurcumin, demethoxycurcumin and curcumin were linear over the concentration range of 2–1000 ng/mL (r2, 0.9951), 2–1000 ng/mL (r2, 0.9970) and 2-1000 ng/mL (r2, 0.9906) respectively.

Intra-assay and inter-assay accuracy in terms of % bias for curcumin was in between −7.95to +6.21, and −7.03 to + 6.34; for demethoxycurcumin was −6.72 to +6.34, and −7.86 to +6.74 and for bisdesmetoxycurcumin was −8.23 to +6.37 and −8.47 to +7.81. The lower limit of quantitation for curcumin, demethoxycurcumin and bisdemethoxycurcumin was 2.0 ng/mL. Analytes were stable under various conditions (in autosampler, during freeze-thaw, at room temperature, and under deep-freeze conditions). This validated method was used during pharmacokinetic studies of curcumin in the mouse plasma.

Conclusions

A specific, accurate and precise UPLC-qTOF-MS/MS method for the determination of curcumin, demethoxycurcumin and bisdemethoxycurcumin both individually and simultaneously was optimized.

Antioxidant activity assay based on the inhibition of oxidation and photobleaching of L-cysteine-capped CdTe quantum dots

Quantum dots (QDs) have recently been the focus of attention of many investigators for development of diagnostic tools in many research areas. In this work, we established a new QD-based assay to evaluate the antioxidant/polyphenolic activity. This assay is based on measurement of the inhibitory effect of the antioxidant/polyphenolic compounds on the UV-induced bleaching of CdTe QDs with L-cysteine capping. QDs exhibited excellent photostability without any UV exposure, while they bleached rapidly under UV irradiation. Generation of reactive oxygen species (ROS) under UV irradiation is probably the main cause of the photobleaching of QDs. By comparing the photostability of QDs in buffer solution in the absence and presence of sodium azide, as a known (1)O(2) quencher, the involvement of (1)O(2) in photobleaching of QDs was confirmed. The photobleaching effect induced by ROS could be reduced in the presence of antioxidant/polyphenolic compounds. We tested several antioxidant/polyphenolic compounds as well as known antioxidants such as trolox and 4 different types of tea. The results obtained by the QD-based assay revealed a very good correlation with the data acquired by Folin-Ciocalteu assay. Furthermore, a deeper understanding of the mechanism and the solution for photobleaching of QDs under UV irradiation might be very meaningful in promoting their clinical applications.