Antioxidant, Free Radical Scavenging and Anti-Inflammatory Effects of Aloesin Derivatives in Aloe vera

Abstract

Antioxidant components in Aloe vera were examined for lipid peroxidation using rat liver microsomal and mitochondrial enzymes. Among the aloesin derivatives examined, isorabaichromone showed a potent antioxidative activity. The DPPH radical and superoxide anion scavenging activities were determined. As one of the most potent components, isorabaichromone together with feruloylaloesin and p-coumaroylaloesin showed potent DPPH radical and superoxide anion scavenging activities. Electron spin resonance (ESR) using the spin trapping method suggested that the potent superoxide anion scavenging activity of isorabaichromone may have been due to its caffeoyl group. As A. vera has long been used to promote wound healing, the inhibitory effects of aloesin derivatives for cyclooxygenase (Cox)-2 and thromboxane (Tx) A₂ synthase were examined and the participation of p-coumaroyl and feruloyl ester groups in the aloesin skeleton was demonstrated. These findings may explain, at least in part, the wound healing effects of A.vera.

Abbreviations

ADP:adenosine diphosphate

ASA:ascorbic acid

BHT:butylated hydroxytoluene

BSA:bovine serum albumin

DMPO:5,5-dimethyl-1-pyrroline N-oxide

DPPH:1,1-diphenyl-2-picrylhydrazyl

EDTA:edetic acid

HEPES:N-(2-hydroxyethyl)-piperazine-N-2′-ethane-sulfonic acid

NADH:reduced nicotinamide adenine dinucleotide

NADPH:reduced nicotinamide adenine dinucleotide phosphate

NBT:nitroblue tetrazolium

Pg:prostaglandin

SOD:superoxide dismutase

TBA:thiobarbituric acid

TCA:trichloroacetic acid

XOD:xanthine oxidase

Key words

Aloe vera - Asphodelaceae - isorabaichromone - antioxidants - free radical - ESR - anti-inflammatory

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