Popular Dietary Supplement Research Articles

Review on cell models to evaluate the potential antioxidant activity of polysaccharides.

Owing to various health functions, natural polysaccharides are becoming a kind of popular dietary nutritional supplement. At present, the occurrence of many chronic diseases is closely related to excessive reactive oxygen species (ROS). Note that polysaccharides with anti-oxidative activity have been paid significant attention as medicines, cosmetics, and food. Many documents constantly prove the effects of antioxidant polysaccharides against Alzheimer's disease, diabetes, and cardiovascular disease. Moreover, the structural features and functional properties of antioxidant polysaccharides have been extensively studied. Many chemical and biological methods have been used to evaluate the antioxidant activity of polysaccharides. Because of deficiencies in the accuracy and authenticity of the chemiluminescence method, the use of cell models has gradually become the mainstream method based on providing a more real biological environment. For these reasons, this study summarizes an overview of recent advances in cell models to evaluate the potential antioxidant activity of the polysaccharides. This study focuses on the advancements in the types of cell models and evaluation of the indexes of the potential mechanisms and factors that influence the anti-oxidative activity of polysaccharides. The aim is to provide useful background and updated information for further development and application of antioxidant polysaccharides.

Aloe Metabolites Prevent LPS-Induced Sepsis and Inflammatory Response by Inhibiting Mitogen-Activated Protein Kinase Activation.

Aloe, a polyphenolic anthranoid-containing Aloe vera leaves, is a Chinese medicine and a popular dietary supplement worldwide. In in vivo situations, polyphenolic anthranoids are extensively broken down into glucuronides and sulfate metabolites by the gut and the liver. The anti-inflammatory potential of aloe metabolites has not been examined. The aim of this study was to investigate the anti-inflammatory effects of aloe metabolites from in vitro (lipopolysaccharides (LPS)-activated RAW264.7 macrophages) and ex vivo (LPS-activated peritoneal macrophages) to in vivo (LPS-induced septic mice). The production of proinflammatory cytokines (TNF-[Formula: see text] and IL-12) and NO was determined by ELISA and Griess reagents, respectively. The expression levels of iNOS and MAPKs were analyzed by Western blot. Our results showed that aloe metabolites inhibited the expression of iNOS, decreased the production of TNF-[Formula: see text], IL-12, and NO, and suppressed the phosphorylation of MAPKs by LPS-activated RAW264.7 macrophages. In addition, aloe metabolites reduced the production of NO, TNF-[Formula: see text] and IL-12 by murine peritoneal macrophages. Furthermore, aloe administration significantly reduced the NO level and exhibited protective effects against sepsis-related death in LPS-induced septic mice. These results suggest that aloe metabolites exerted anti-inflammatory effects in vivo, and that these effects were associated with the inhibition of inflammatory mediators. Therefore, aloe could be considered an effective therapeutic agent for the treatment of sepsis.

Chemical properties and biotoxicity of several chromium picolinate derivatives

As a man-made additive, chromium picolinate Cr(pic)3 has become a popular dietary supplement worldwide. In this paper Cr(pic)3 and its new derivatives Cr(6-CH3-pic)3 (1), [Cr(6-NH2-pic)2(H2O)2]NO3 (2) and Cr(3-NH2-pic)3 (3) were synthesized, and complexes 1 and 2 were characterized by X-ray crystal structure (where pic=2-carboxypyridine). The relationship between the chemical properties and biotoxicity of these complexes was fully discussed: (1) The dynamics stability of chromium picolinate complexes mainly depends on the CrN bonds length. (2) There is a positive correlation between the dynamics stability, electrochemical potentials and generation of reactive oxygen species through Fenton-like reaction. (3) However, no biological toxicity was observed through MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) and sub-chronic oral toxicity study for these chromium picolinate compounds. Together, our findings establish a framework for understanding the structure-property-toxicity relationships of the chromium picolinate complexes.

210Pb in magnesium dietary supplements

ABSTRACTThe idea behind this study was to investigate the most popular magnesium dietary supplements as a potential additional source of 210Pb in the human diet. The paper presents the results of 210Pb activities determined in different magnesium supplements, as well as an estimation of the annual effective radiation doses from 210Pb decay. The results showed that the highest value of 210Pb activity was found in a magnesium supplement of natural origin (dolomite) with a value of 2.97 ± 0.18 mBq g–1. The highest annual radiation dose from 210Pb obtained from the magnesium daily recommended value (0.4 g of pure Mg) was calculated for dolomite tablets as 3.71 ± 0.02 µSv·year–1.

Vitamin-Mineral Supplement Use Patterns in Elderly Koreans: Data from the 2007-2008 Korean National Health and Nutrition Examination Survey.

BackgroundVitamin-mineral supplements are the most popular dietary supplements in Korea. However, few studies have assessed the relationship between vitamin-mineral supplementation and associated factors among the Korean elderly. The purpose of this study was to assess the use of vitamin-mineral supplements among elderly in Korea as well as its association with sociodemographic factors, health-related behaviors, medical conditions, and nutrient intake.MethodsThis study was based on data from the Korean National Health and Nutrition Examination Survey, conducted by the Korean Ministry of Health and Welfare from 2008 to 2009. Data from 3,294 elderly men and women (65 years of age and older) were analyzed. Multivariable-weighted logistic regression model analysis was used to evaluate the association between vitamin-mineral supplement use and sociodemographic factors, health-related habits, and medical conditions.ResultsVitamin-mineral supplementation was reported by 16.3% of the participants. The most common reason for using dietary supplements was recommendations from friends and acquaintances. Highly educated person, female participants had a greater likelihood of taking vitamin-mineral supplements. In addition, analysis of nutrient intake from food sources alone revealed a lower proportion of vitamin-mineral supplement users with nutrient intakes below the estimated average requirements for vitamin A, vitamin C, thiamine, riboflavin, niacin, calcium, iron, and phosphorus, compared to nonusers. However, vitamin-mineral supplementation was not associated with health-related behaviors or medical conditions.ConclusionHighly educated person, elderly Korean women had a greater likelihood of using vitamin-mineral supplements. In addition, nutrient intakes from food sources alone were significantly higher among vitamin-mineral supplement users. Finally, vitamin-mineral supplementation may be an indicator of healthier diet in elderly Koreans.

Caffeine and Creatine Content of Dietary Supplements Consumed by Brazilian Soccer Players.

Caffeine and creatine are ingredients in the most popular dietary supplements consumed by soccer players. However, some products may not contain the disclosed amounts of the ingredients listed on the label, compromising the safe usage and the effectiveness of these supplements. Therefore, the aim of this study was to evaluate the content of caffeine and creatine in dietary supplements consumed by Brazilian soccer players. The results obtained were compared with the caffeine content listed on the product label. Two batches of the supplement brands consumed by ≥ 50% of the players were considered for analysis. The quantification of caffeine and creatine in the supplements was determined by a high-performance liquid chromatography system with UV detector. Nine supplements of caffeine and 7 supplements of creatine met the inclusion criteria for analysis. Eight brands of caffeine and five brands of creatine showed significantly different values (p < .05) as compared with the values stated on the label. There were no significant differences between the two batches of supplements analyzed, except for one caffeine supplement. It can be concluded that caffeine and creatine dietary supplements consumed by Brazilian soccer players present inaccurate values listed on the label, although most presented no difference among batches. To ensure consumer safety and product efficacy, accurate information on caffeine and creatine content should be provided on all dietary supplement labels.

Arginine behaviour after arginine or citrulline administration in older subjects.

Arginine (ARG) and its precursor citrulline (CIT) are popular dietary supplements, especially for the elderly. However, age-related reductions in lean body mass and alterations in organ functions could change their bioavailability. Pharmacokinetics and tolerance to amino acid (AA) loads are poorly documented in elderly subjects. The objective here was to characterise the plasma kinetics of CIT and ARG in a single-dosing study design. Eight fasting elderly men underwent two separate isomolar oral loading tests (10 g of CIT or 9·94 g of ARG). Blood was withdrawn over an 8-h period to measure plasma AA concentrations. Only CIT, ornithine and ARG plasma concentrations were changed. Volume of distribution was not dependent on AA administered. Conversely, parameters related to ARG kinetics were strongly dependent on AA administered: after ARG load, elimination was higher (ARG>CIT; P=0·041) and admission period+time at peak concentration was lower (ARG<CIT; P=0·033), and the combination of both phenomena results in a marked increase in ARG availability when CIT was administered (ARG<CIT; P=0·033) compared with ARG administration itself. In conclusion, a single CIT administration in the elderly is safe and well tolerated, and CIT proves to be a better in vivo ARG precursor than ARG itself in healthy elderly subjects.

Effects of acute ingestion of a multi-ingredient pre-workout supplement on lower body power and anaerobic sprint performance

Background Multi-ingredient pre-workout supplements (MIPS) are becoming popular dietary supplements among strength and power athletes. These products frequently include caffeine, creatine, beta-alanine, and branched-chain amino acids as the primary ingredients. When studied on an individual basis, several of these ingredients have been shown to increase muscular power following acute ingestion; however, little is known in regard to a synergistic effect when said ingredients are combined. The purpose of this study was to determine if short-term, MIPS ingestion influences muscular power and anaerobic sprint performance.

Weighing the Benefits of Fish Oil for Patients With Prostate Cancer: A Subcohort Review From the SELECT Trial.

© 2015 Harborside Press® Many individuals, both men and women, seek dietary supplements with the belief that they will protect them from developing certain chronic diseases and possibly even decrease their risk of developing cancer (National Cancer Institute, 2015). Fish oil is of the most popular dietary supplements, containing two of the most important omega-3 acids: eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Humans cannot produce their own omega-3 fatty acids or make them from omega-6 fatty acids. Therefore, external intake of these acids is important to one’s health. Two external means of obtaining omega-3 fatty acids in diet are eating cold water fish such as salmon, sardines, herring, mackerel, tuna, or anchovy or taking fish oil supplements. Sometimes, oral fish oil supplements contain tiny amounts of vitamin E to prevent spoilage and other minerals such as calcium and iron, or they are orally mixed with vitamins A, B1, B2, B3, C, or D. It is necessary for patients and advanced practitioners to read supplement labels. Also, preparation of fish (broil or baked, not fried) is important to obtain the maximal benefit of the omega-3 fatty acids. Fish oil has long been taken for various conditions. Scientific evidence suggests that omega-3 fatty acids can reduce pain, swelling, and inflammation (Goldberg & Katz, 2007; Maroon & Bost, 2006). Strong evidence supports the idea that fish oil helps to lower high-density proteins and the risk of heart disease and stroke (Natural Medicines Comprehensive Database, 2015). There is ongoing research on the use of fish oil for other purposes.

Ventricular Tachycardia Precipitated by the Use of the Diet Supplement Hydroxycut Gummies.

Dietary supplements have a long history of causing adverse effects. Ventricular arrhythmias have not been described with Hydroxycut Gummies. To report a case of ventricular arrhythmia after prolonged use of a popular dietary supplement, Hydroxycut Gummies. An 18-year-old female with no significant past medical history presented with life-threatening ventricular arrhythmia following about 10 days of use of Hydroxycut Gummies, a legal dietary supplement previously unreported to cause this complication. The patient received external cardioversion due to progressive decline in mental status and persistent hypotension and was initiated on intravenous procainamide at an outside hospital. Left ventricular ejection fraction was 45% to 50%, and cardiac MRI showed no definite finding of infarct, myocarditis, or fibrosis. Beta-blocker therapy was initiated, and there was a progressive reduction in ventricular arrhythmia burden with an improvement of symptoms over the next few days. Two and a half months after the initial hospitalization, follow-up Holter monitor revealed occasional accelerated idioventricular rhythm events and a significant reduction in, but still occasional, long monomorphic ventricular tachycardia events. None of the ingredients listed in this product have been associated with cardiac dysrhythmias in the literature. One phytochemical potentially in the product is alpha-quinidine, which could be the cause of the adverse event. However, there was no other identifiable etiology for the ventricular tachycardia, which resolved after the discontinuation of supplement and the addition of beta-blocker therapy. Hydroxycut Gummies should be considered a probable cause of this patient's arrhythmia given the lack of another etiology and a Naranjo Scale score of 6.

A validated method for determination of cannabinoid content in dietary supplements by UPLC-MS

Natural products containing cannabinoids derived from Cannabis sativa (L.), a medicinal plant with a long history of ethnobotanical uses, are now emerging as popular dietary supplements in the consumer marketplace. In spite of the ambiguous interpretation of the federal legal status, cannabinoid products are now readily available from online outlets and are increasingly being marketed by mainstream retailers. Many states have enacted legislation conferring various levels of legal status to Cannabis, and in recent months thirteen states have passed so called "low-THC" or "CBD-only" laws to allow widespread access to certain natural products that are less contentious in terms of the current Schedule I classification by the federal Controlled Substances Act. Although techniques exist for quantification of cannabinoids in crude plant materials as well as in blood and urine, dietary supplements present analytical challenges due to complex matrices and the inherent variability of bioactive forms with oral delivery. Reported here is a validated method for rapid determination of cannabidiol (CBD), cannabidiolic acid (CBD-A), Δ9-tetrahydrocannabinol (THC), Δ9-tetrahydrocannabinolic acid (THC-A) and cannabigerol using UPLC with detection by photo-diode array and single quadrupole mass spectrometry.

Growth-suppressive effect of berberine on endometrial carcinoma cells: Role of mitochondrial and PI3K/Akt pathway

Berberine is an isoquinoline alkaloid and a popular dietary supplement in the US market for lowering blood glucose and managing a healthy lipid profile. The anti-tumour activity of berberine is also known. Endometrial cancer is a gynecological malignancy tumour. Our study demonstrated for the first time that berberine could be used to inhibit endometrial carcinoma cell proliferation in vitro and unveiled the relevant mechanisms. By flow cytometry, we found that berberine affected cell cycle distribution in endometrial cancer cells. Additionally, berberine could induce cell apoptosis through activation of the mitochondrial/caspase pathway. We further investigated berberine-mediated signal transduction in endometrial cancer cells and found that berberine engaged in the PI3K/Akt pathway, a cell proliferation- and cell cycle progression-related signalling pathway. Our results suggest that berberine could be used as a potential dietary supplement or functional food ingredient to prevent endometrial cancer.

Rapid and sensitive analysis of reduced and oxidized coenzyme Q10 in human plasma by ultra performance liquid chromatography-tandem mass spectrometry and application to studies in healthy human subjects

Coenzyme Q10 is an endogenous antioxidant as well as a popular dietary supplement. In blood circulation, coenzyme Q10 exists predominantly as its reduced ubiquinol-10 form, which readily oxidizes to ubiquinone-10 ex vivo. Plasma concentrations of coenzyme Q10 reflect net overall metabolic demand, and the ratio of ubiquinol-10:ubiquinone-10 has been established as an important biomarker for oxidative stress. However, the lability of ubiquinol-10 makes accurate determination of both forms of coenzyme Q10 difficult. Ex vivo oxidation of ubiquinol-10 to ubiquinone-10 during sample collection, processing and analysis may obfuscate the invivo ratio. We developed a rapid and sensitive method for the determination of ubiquinol-10 and ubiquinone-10 in human plasma, using coenzyme Q9 analogues as internal standards. Single-step protein precipitation in 1-propanol, a lipophilic and water-soluble alcohol, allowed for rapid extraction. Analysis by ultra performance liquid chromatography-tandem mass spectrometry provided rapid run-time and high sensitivity, with lower limits of quantitation for ubiquinol-10 and ubiquinone-10 of 5 μg/L and 10 μg/L, respectively. This method is suitable for clinical studies with coenzyme Q10 supplementation in various disease states where this lipid-antioxidant may be beneficial. We have applied this method to >300 plasma samples from coenzyme Q10 research studies in chronic haemodialysis patients and postsurgical patients.

Studies on Pharmacokinetic Drug Interaction Potential of Vinpocetine.

BackgroundVinpocetine, a semi-synthetic derivative of vincamine, is a popular dietary supplement used for the treatment of several central nervous system related disorders. Despite its wide use, no pharmacokinetic drug interaction studies are reported in the literature. Due to increasing use of dietary supplements in combination with conventional drugs, the risk of adverse effects is on the rise. As a preliminary step to predict a possibility of drug interaction during concomitant use of vinpocetine and conventional drugs, this study was carried out to evaluate the effects of vinpocetine on three main regulators of pharmacokinetic drug interactions namely, cytochromes P450 (CYPs), P-glycoprotein (P-gp), and Pregnane X receptor (PXR).MethodsInhibition of CYPs was evaluated by employing recombinant enzymes. The inhibition of P-gp was determined by calcein-AM uptake method in transfected and wild type MDCKII cells. Modulation of PXR activity was monitored through a reporter gene assay in HepG2 cells.ResultsVinpocetine showed a strong inhibition of P-gp (EC50 8 μM) and a moderate inhibition of recombinant CYP3A4 and CYP2D6 (IC50 2.8 and 6.5 μM) with no activity towards CYP2C9, CYP2C19 and CYP1A2 enzymes. In HLM, competitive inhibition of CYP3A4 (IC50 54 and Ki 19 μM) and non-competitive inhibition of CYP2D6 (IC50 19 and Ki 26 μM) was observed. Activation of PXR was observed only at the highest tested concentration of vinpocetine (30 μM) while lower doses were ineffective.ConclusionStrong inhibition of P-gp by vinpocetine is indicative of a possibility of drug interactions by altering the pharmacokinetics of drugs, which are the substrates of P-gp. However, the effects on CYPs and PXR indicate that vinpocetine may not affect CYP-mediated metabolism of drugs, as the inhibitory concentrations are much greater than the expected plasma concentrations in humans.

Safety of Popular Herbal Supplements in Lactating Women.

The increasing popularity and use of dietary supplements has required health care professionals to become more knowledgeable of their properties, interactions, and adverse effects. The objectives of this review were to evaluate the safety of popular dietary supplements in breastfeeding mothers and the effects on the infants. Nine of the most popular herbal dietary supplements were identified based on the 2011 US market report of the top 10 selling botanicals and the most frequently received inquiries by the Ruth A. Lawrence Lactation Study Center at the University of Rochester Medical Center. Relevant publications were identified through June 2014 using PubMed and EMBASE; tertiary references, including the Drugs and Lactation Database and Natural Medicine Comprehensive Database, were also reviewed. These herbals include black cohosh, cranberry, echinacea, evening primrose, garlic, ginseng, melatonin, milk thistle, and St John's wort. Studies varied greatly with regard to study design, herbal intervention, and outcome measures. Findings suggested that dietary/herbal supplements have not been evaluated in high-quality clinical trials, and there is limited evidence supporting safety of use, particularly among lactating women. Therefore, it is essential for physicians to provide counseling for nursing mothers seeking information on dietary supplements, highlighting reliable safety profiles, inquiring about the potential benefits the patient is seeking, and assessing the patient's perception of this supplement during breastfeeding. More research and clinical trials are required in this area to guide the recommendations and expand our current knowledge of these products.

A molecular docking study of phytochemical estrogen mimics from dietary herbal supplements.

PurposeThe purpose of this study is to use a molecular docking approach to identify potential estrogen mimics or anti-estrogens in phytochemicals found in popular dietary herbal supplements.MethodsIn this study, 568 phytochemicals found in 17 of the most popular herbal supplements sold in the United States were built and docked with two isoforms of the estrogen receptor, ERα and ERβ (a total of 27 different protein crystal structures).ResultsThe docking results revealed six strongly docking compounds in Echinacea, three from milk thistle (Silybum marianum), three from Gingko biloba, one from Sambucus nigra, none from maca (Lepidium meyenii), five from chaste tree (Vitex agnus-castus), two from fenugreek (Trigonella foenum-graecum), and two from Rhodiola rosea. Notably, of the most popular herbal supplements for women, there were numerous compounds that docked strongly with the estrogen receptor: Licorice (Glycyrrhiza glabra) had a total of 26 compounds strongly docking to the estrogen receptor, 15 with wild yam (Dioscorea villosa), 11 from black cohosh (Actaea racemosa), eight from muira puama (Ptychopetalum olacoides or P. uncinatum), eight from red clover (Trifolium pratense), three from damiana (Turnera aphrodisiaca or T. diffusa), and three from dong quai (Angelica sinensis). Of possible concern were the compounds from men’s herbal supplements that exhibited strong docking to the estrogen receptor: Gingko biloba had three compounds, gotu kola (Centella asiatica) had two, muira puama (Ptychopetalum olacoides or P. uncinatum) had eight, and Tribulus terrestris had six compounds.ConclusionsThis molecular docking study has revealed that almost all popular herbal supplements contain phytochemical components that may bind to the human estrogen receptor and exhibit selective estrogen receptor modulation. As such, these herbal supplements may cause unwanted side effects related to estrogenic activity.

D-Ribose Supplementation in the Equine: Lack of Effect on Glycated Plasma Proteins Suggesting Safety in Humans

Background: d-Ribose is a popular dietary supplement for humans and the equine because of its crucial role in cellular bioenergetics. However, as a reducing sugar, it has been suggested that ingestion of d-ribose might promote the formation of glycated proteins in vivo with potential adverse consequences.Objective: The aim of this study was to examine if d-Ribose would promote the formation of glycated proteins in vivo following exercise in training thoroughbred racehorses.Methods: Two groups of horses received the supplement (30 and 50 g d-Ribose daily) for 17 weeks, during which period the horses were subjected to low-intensity exercises followed by high-intensity exercises. Blood samples were analyzed for glycated plasma proteins at baseline and following the 2 exercise regimens.Results: This study shows that long-term ingestion of d-Ribose at 30-50 g a day does not promote the formation of glycated plasma proteins in thoroughbred racehorses. Ribose supplementation also protected the horses from cramping while enhancing muscle recovery at the same time. No adverse effects were reported.Conclusion: Ribose supplementation is safe and does not cause glycation in vivo. This investigation also establishes safety of d-Ribose in thoroughbred racehorses, suggesting similar implications in humans as well.

Pro-inflammatory properties of shark cartilage supplement

The erosion and breakdown of cartilage is generally recognized to be an integral manifestation of arthritic disease, which is often accompanied by the development and progression of inflammation associated with it. Commercial shark cartilage (SC) is a popular dietary supplement taken for the prevention and/or control of chronic disease, including arthritis. The efficacy of SC in maintaining joint health remains questionable; there is a lack of sufficient reliable information on its effect on immunocompetent cells, and the potential health risks involved have not been adequately assessed. Our earlier in vitro studies showed that SC extracts induce a Th1-type inflammatory cytokine response in human leucocytes, and collagen type II alpha 1 protein was shown to be an active cytokine-inducing component in SC. In this study, we further define the cellular response to SC stimulation by classifying leucocytes into primary and secondary responders employing enriched leucocyte subpopulations. Inhibitors of specific signaling pathways were used to verify the functional effect of SC on specific pathway(s) utilized. Results indicate the monocyte/macrophage as the initially responding cell, followed by lymphocytes and the production of interferon-γ. Chemokines, MCP-1 and RANTES, were produced at significant levels in stimulated leucocyte cultures. Initial cellular activation is likely followed by activation of Jun Kinase and p38 mitogen-activated protein kinase signal transduction pathways. This study presents evidence of significant immunological reactivity of components of commercial SC supplement, which could pose a potential health risk for consumers, particularly those with underlying inflammatory disease such as irritable bowel syndrome and arthritis.

Nitrogen-Containing Constituents of Black Cohosh: Chemistry, Structure Elucidation, and Biological Activities.

The roots/rhizomes of black cohosh (Actaea racemosa L. syn. Cimicifuga racemosa [L]. Nutt., Ranunculaceae) have been used traditionally by Native Americans to treat colds, rheumatism, and a variety of conditions related to women's health. In recent years black cohosh preparations have become popular dietary supplements among women seeking alternative treatments for menopausal complaints. The popularity of the plant has led to extensive phytochemical and biological investigations, including several clinical trials. Most of the phytochemical and biological research has focused on two abundant classes of compounds: the triterpene glycosides and phenolic acids. A third group of phytoconstituents that has received far less attention consists of the alkaloids and related compounds that contain nitrogen. This chapter summarizes the current state of knowledge of the chemistry and biological activities associated with this group of constituents and provides some perspective on their significance for future research on this interesting plant.

Monoamine oxidase inhibitory constituents of propolis: kinetics and mechanism of inhibition of recombinant human MAO-A and MAO-B.

Propolis is the resinous material that bees gather from leaf buds, flowers and vegetables. Propolis extracts contain constituents with a broad spectra of pharmacological properties and are important ingredients of popular dietary supplements. Propolis extracts were evaluated in vitro for inhibition of recombinant human monoamine oxidase (MAO)-A and MAO-B. The dichloromethane extract of propolis showed potent inhibition of human MAO-A and MAO-B. Further fractionation identified the most active fractions as rich in flavonoids. Galangin and apigenin were identified as the principal MAO-inhibitory constituents. Inhibition of MAO-A by galangin was about 36 times more selective than MAO-B, while apigenin selectivity for MAO-A vs. MAO-B was about 1.7 fold. Apigenin inhibited MAO-B significantly more potently than galangin. Galangin and apigenin were further evaluated for kinetic characteristics and the mechanism for the enzymes’ inhibition. Binding of galangin and apigenin with MAO-A and -B was not time-dependent and was reversible, as suggested by enzyme-inhibitor binding and dissociation-dialysis assay. The inhibition kinetics studies suggested that galangin and apigenin inhibited MAO-A and -B by a competitive mechanism. Presence of prominent MAO inhibitory constituents in propolis products suggests their potential for eliciting pharmacological effects that might be useful in depression or other neurological disorders. The results may also have important implications in drug-dietary supplement interactions.