ascorbic-acid and epicatechin-gallate

In the United States, nearly 44,000 people are diagnosed with oral or pharyngeal cancer annually. The life expectancy for those who are diagnosed have a survival rate of 57% after five years. Among them, oral cancer can be classified as benign or malignant tumors and is diagnosed at several stages in the development: premalignant conditions, premalignant lesions, and malignant cancer. The early signs of oral cancer often go unnoticed by the individual and are often discovered during routine dental examinations. Early detection and treatment may help to increase patient survival rates. The most widely used treatments for oral cancer include surgery, radiation, and chemotherapy-alone or in combination. Preclinical and clinical evidence for the use of green tea, raspberry, asparagus, and cannabis extracts is discussed in this review. Diet changes, supplementation with antioxidants, high-dose vitamin C therapy, and cannabinoid use have been suggested to decrease cancer cell replication and increase chance of remission. Early detection and lifestyle changes, including the use of dietary supplements in at-risk populations, are critical steps in preventing and successfully treating oral cancer. The main evidence for supplement use is currently in cancer prevention rather than treatment. Further research, determination, and mechanism of action for bioactive compounds such as epigallocatechin, epicatechin-3-gallate, and Bowman-Birk inhibitor concentrate, through in vitro, in vivo, and clinical trials need to be completed to support the use of natural products and their effectiveness in preventative care and supporting therapeutic approaches.

Topics: Anthocyanins; Antioxidants; Ascorbic Acid; Asparagus Plant; Cannabinoids; Carotenoids; Catechin; Complementary Therapies; Dietary Supplements; Dose-Response Relationship, Drug; Glycine max; Humans; Lycopene; Mouth Neoplasms; Phytotherapy; Tea

The effect of green tea formulated with vitamin C and xylitol on intestinal cell transport of gallated and nongallated catechin was studied. The transport of catechins from both apical to basolateral and basolateral to apical directions was measured. The effect of vitamin C (4, 10, 20 ppm), xylitol (11, 27.5, 55 ppm), and combinations of both on the intestinal transport rate of catechins was examined. The efflux value (Pb→a/Pa→b) of (-)-epigallocatechin (EGC), (-)-epigallocatechin gallate (EGCG), (-)-epicatechin (EC), and (-)-epicatechin gallate (ECG) was 0.26, 0.22, 1.22, and 0.17, respectively, indicating that EC appeared to be less absorbed compared with other catechins. The addition of xylitol (11, 27.5, 55 ppm) and vitamin C (4, 10, 20 ppm) and in combination enhanced transport rate of nongallated catechins such as EC and EGC. For EC, vitamin C was revealed to be the most effective on intestinal transport, implying the inhibition of the efflux transport mechanism of EC. Intestinal transport of gallated catechins significantly increased from catechins formulated with vitamin C and xylitol in a dose-dependent manner compared to the catechin-only formulation. Results provide a potential strategy to enhance the delivery and bioavailability of catechins in humans by modulating green tea formulation with vitamin C and xylitol.

Topics: Antioxidants; Ascorbic Acid; Biological Availability; Caco-2 Cells; Catechin; Chemistry, Pharmaceutical; Chromatography, High Pressure Liquid; Humans; Intestinal Absorption; Intestinal Mucosa; Intestines; Mass Spectrometry; Plant Extracts; Tea; Xylitol

The synergistic antioxidant effect of polyphenols extracted from green tea, i.e. (-)-epicatechin (EC), (-)-epigallocatechin (EGC), (-)-epicatechin gallate (ECG), (-)-epigallocatechin gallate (EGCG) and gallic acid (GA), with alpha-tocopherol (vitamin E) and L-ascorbic acid (vitamin C) against the peroxidation of linoleic acid has been studied in sodium dodecyl sulfate (SDS) micelles. The peroxidation was initiated thermally by a water-soluble azo initiator 2,2'-azobis(2-amidinopropane) hydrochloride (AAPH), and the reaction kinetics were studied by monitoring the formation of linoleic acid hydroperoxides and consumption of the antioxidants. It was found that the mixture of the green tea polyphenol, vitamin E and vitamin C could act synergistically to protect lipid peroxidation. Kinetic and mechanistic studies on the antioxidation process revealed that this antioxidant synergism was due to the regeneration of vitamin E by the green tea polyphenol and the regeneration of the latter by vitamin C.

Topics: alpha-Tocopherol; Antioxidants; Ascorbic Acid; Catechin; Complex Mixtures; Flavonoids; Free Radicals; Half-Life; Kinetics; Linoleic Acid; Lipid Peroxidation; Micelles; Phenols; Polyphenols; Sodium Dodecyl Sulfate; Tea

The effect of photosensitized oxidation of conjugated linoleic acid in an oil-in-water (o/w) emulsion system was studied. Water-soluble natural antioxidants, including apple polyphenols from apple extract, green tea extract, 4-hydroxy-2(or 5)-ethyl-5(or2)-methyl-3(2H)-furanone(HEMF), 4-hydroxy-2,5-dimethyl-3(2H)-furanone (HDMF), and ascorbic acid, were tested for antioxidant activity in this system. The green tea extract showed the highest antioxidant activity followed by ascorbic acid. Apple polyphenols did not give significant antioxidant activity. HEMF and HDMF exhibited a prooxidant effect. The antioxidant activity of tea catechins was also investigated. Of them, EGCG and ECG exhibited antioxidant activity at 50 ppm, but the antioxidant activity between them was not significantly different (P < 0.05). Comparatively, EC, EGC, and GCG showed no significant antioxidative effect at 50 ppm. When the concentration increased to 100 ppm, the antioxidant activity of ECG and EGCG significantly increased compared with that at 50 ppm, and EGCG had higher antioxidant activity than ECG. GCG also showed significant antioxidant activity at 100 ppm. EGCG exhibited the highest antioxidant activity among the tea catechins in the emulsion system at 100 ppm.

Topics: Antioxidants; Ascorbic Acid; Catechin; Emulsions; Flavonoids; Fruit; Furans; Light; Linoleic Acids, Conjugated; Oxidation-Reduction; Phenols; Polyphenols; Singlet Oxygen; Solubility; Vitis; Water

Kinetic study of the aroxyl radical-scavenging action of catechins (epicatechin (EC), epicatechin gallate (ECG), epigallocatechin (EGC), and epigallocatechin gallate (EGCG)) and related compounds (methyl gallate (MG), 4-methylcatechol (MC), and 5-methoxyresorcinol (MR)) has been performed. The second-order rate constant ( k s) for the reaction of these antioxidants with aroxyl radical has been measured in ethanol and aqueous Triton X-100 micellar solution (5.0 wt %). The k s values decreased in the order of EGCG > EGC > MC > ECG > EC > MG >> MR in ethanol, indicating that the reactivity of the OH groups in catechins decreased in the order of pyrogallol B-ring > catechol B-ring > gallate G-ring > resorcinol A-ring. The structure-activity relationship in the free radical-scavenging reaction by catechins has been clarified by the detailed analyses of the pH dependence of k s values. From the results, the p K a values have been determined for catechins. The monoanion form at catechol B- and resorcinol A-rings and dianion form at pyrogallol B- and gallate G-rings show the highest activity for free radical scavenging. It was found that the free radical-scavenging activities of catechins are 3.2-13 times larger than that of vitamin C at pH 7.0.

Topics: Ascorbic Acid; Catechin; Ethanol; Free Radical Scavengers; Hydrogen-Ion Concentration; Kinetics; Micelles; Reactive Oxygen Species; Solutions

Blood plasma was incubated with 50 mM AAPH [2, 2'-azobis-(2-amidinopropane) hydrochloride] in the absence or presence of catechins (5-100 microM). Lipid oxidation was evaluated by measuring the formation of 2-thiobarbituric acid reactive substances (TBARS). The concentration of alpha-tocopherol (AT), beta-carotene (BC), ascorbic acid (AA), and catechins was determined by reverse phase high performance liquid chromatography (HPLC) with electrochemical detection. All the assayed catechins inhibited plasma TBARS formation. Based on the calculated IC50, the order of effectiveness was: epicatechin gallate (ECG) > epigallocatechin gallate (EGCG) > epigallocatechin (EGC) > epicatechin (EC) > catechin (C). Catechins protected plasma AT and BC from AAPH-mediated oxidation. The order of effectiveness for AT protection was ECG > EGCG > EC = C > EGC; and for BC protection, the order was EGCG > ECG > EGC > > EC > C. The addition of catechins modified the kinetics of TBARS formation and AT depletion, but the rate of AA depletion was not affected. Catechin oxidation did not start until the complete depletion of AA, and it preceded AT depletion. These results indicate that catechins are effective antioxidants in human blood plasma, delaying the lipid oxidation and depletion of endogenous lipid-soluble antioxidants (AT and BC).

Topics: Ascorbic Acid; beta Carotene; Catechin; Chromatography, High Pressure Liquid; Dose-Response Relationship, Drug; Flavonoids; Humans; Kinetics; Lipid Peroxidation; Thiobarbituric Acid Reactive Substances; Vitamin E