Ramalin, a novel nontoxic antioxidant compound from the Antarctic lichen Ramalina terebrata

Abstract

Ramalin (-y-glutamyl-N？-(2-hydroxyphenyl)hydrazide), a novel compound, was isolated from the methanol？water extract of the Antarctic lichen Ramalina terebrata by several chromatographic meth- ods. The molecular structure of ramalin was determined by spectroscopic analysis. The experimental data showed that ramalin was ？ve times more potent than commercial butylated hydroxyanisole (BHA) in scavenging 1-diphenyl-2-picryl- hydazil (DPPH) free radicals, 27 times more potent in scavenging 2,2？-azino-bis (3- ethylbenzthiazoline-6-sulfonic acid free radicals (ABTS？+ ) than the vitamin E analogue,trolox, and 2.5 times more potent than BHT in reducing Fe3+ to Fe2+ ions. Similarly, ramalin was 1.2 times more potent than ascorbic acid in scavenging superoxide radicals and 1.25 times more potent than commercial kojic acid in inhibiting tyrosinase enzyme activity, which ultimately leads to whiten- ing of skin cells. Ramalin showed no or very little cytotoxicity in human keratinocyte and ？broblast cells at its antioxidant concentration. Furthermore, ramalin was assessed to determine its antioxidant activity in vivo. One microgram per milliliter ramalin signi？cantly reduced the released nitric oxide (NO) and 0.125 fLg/ml ramalin reduced the produced hydrogen peroxide (H2 O2 ) in LPS (lipopolysaccharide)- stimulated murine macrophaure of ramalin was determined by spectroscopic analysis. The experimental data showed that ramalin was ？ve times more potent than commercial butylated hydroxyanisole (BHA) in scavenging 1-diphenyl-2-picryl- hydazil (DPPH) free radicals, 27 times more potent in scavenging 2,2？-azino-bis (3- ethylbenzthiazoline-6-sulfonic acid free radicals (ABTS？+ ) than the vitamin E analogue,trolox, and 2.5 times more potent than BHT in reducing Fe3+ to Fe2+ ions. Similarly, ramalin was 1.2 times more potent than ascorbic acid