Isolation and characterization of flavanols from Anthocephalus cadamba and evaluation of their antioxidant, antigenotoxic, cytotoxic and COX-2 inhibitory activities

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Abstract

ABSTRACT In search of lead molecules for use in disease prevention and as food additive from natural sources, two flavanols were isolated from leaves of Anthocephalus cadamba (Roxb.) Miq., Rubiaceae. Their structures were established as 6-hydroxycoumarin-(4"→8)-(-)-epicatechin and 6-hydroxycoumarin-(4"→8)-(-)-epicatechin-(4→6‴)-(-)-epicatechin on the basis of spectroscopic data. Both the compounds exhibited potent antioxidant and antigenotoxic activity. 6-Hydroxycoumarin-(4"→8)-(-)-epicatechin scavenged DPPH, ABTS+.and superoxide anion radicals with IC50 values of 6.09 µg/ml, 5.95 µg/ml and 42.70 µg/ml respectively whereas the IC50 values for 6-hydroxycoumarin-(4"→8)-(-)-epicatechin-(4→6‴)-(-)-epicatechin were 6.62 µg/ml for DPPH free radicals, 6.93 µg/ml for ABTS radical cations and 49.08 µg/ml for superoxide anion radicals. Both the compounds also exhibited potent reducing potential in reducing power assay and protected the plasmid DNA (pBR322) against the attack of hydroxyl radicals generated by Fenton's reagent in DNA protection assay. In SOS chromotest, 6-hydroxycoumarin-(4"→8)-(-)-epicatechin decreased the induction factor induced by 4NQO (20 µg/ml) and aflatoxin B1 (20 µg/ml) by 31.78% and 65.04% respectively at a concentration of 1000 µg/ml. On the other hand, 6-hydroxycoumarin-(4"→8)-(-)-epicatechin-(4→6‴)-(-)-epicatechin decreased the genotoxicity of these mutagens by 37.11% and 47.05% respectively. It also showed cytotoxicity in COLO-205 cancer cell line with GI50 of 435.71 µg/ml. Both the compounds showed moderate cyclooxygenase-2 inhibitory activity.

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Flavonoids as antioxidants.

Pier-Giorgio Pietta (2000)

Flavonoids are phenolic substances isolated from a wide range of vascular plants, with over 8000 individual compounds known. They act in plants as antioxidants, antimicrobials, photoreceptors, visual attractors, feeding repellants, and for light screening. Many studies have suggested that flavonoids exhibit biological activities, including antiallergenic, antiviral, antiinflammatory, and vasodilating actions. However, most interest has been devoted to the antioxidant activity of flavonoids, which is due to their ability to reduce free radical formation and to scavenge free radicals. The capacity of flavonoids to act as antioxidants in vitro has been the subject of several studies in the past years, and important structure-activity relationships of the antioxidant activity have been established. The antioxidant efficacy of flavonoids in vivo is less documented, presumably because of the limited knowledge on their uptake in humans. Most ingested flavonoids are extensively degraded to various phenolic acids, some of which still possess a radical-scavenging ability. Both the absorbed flavonoids and their metabolites may display an in vivo antioxidant activity, which is evidenced experimentally by the increase of the plasma antioxidant status, the sparing effect on vitamin E of erythrocyte membranes and low-density lipoproteins, and the preservation of erythrocyte membrane polyunsaturated fatty acids. This review presents the current knowledge on structural aspects and in vitro antioxidant capacity of most common flavonoids as well as in vivo antioxidant activity and effects on endogenous antioxidants.

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Revised methods for the Salmonella mutagenicity test

Dorothy M. Maron, Bruce Ames (1983)

The methods for detecting carcinogens and mutagens with the Salmonella mutagenicity test were described previously (Ames et al., 1975b). The present paper is a revision of the methods. Two new tester strains, a frameshift strain (TA97) and a strain carrying an ochre mutation on a multicopy plasmid (TA102), are added to the standard tester set. TA97 replaces TA1537. TA1535 and TA1538 are removed from the recommended set but can be retained at the option of the investigator. TA98 and TA100 are retained. We discuss other special purpose strains and present some minor changes in procedure, principally in the growth, storage, and preservation of the tester strains. Two substitutions are made in diagnostic mutagens to eliminate MNNG and 9-aminoacridine. Some test modifications are discussed.