Antioxidant and Antibacterial Capacities of Fukugetin and Xanthones from Fukugi (Garcinia subelliptica)

Abstract

　We examined the antioxidant and antibacterial capacities of fukugetin and five flavonoids from Fukugi (Garcinia subelliptica). Their capacities were compared with those of known structural analogs. Antioxidant capacities of the compounds were determined using different assays: radical scavenging capacity [2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2-azinobis (3-ethyl-benzothiazoline-6-sulfonic acid) (ABTS)] ; oxygen radical absorbance capacity (ORAC) ; and superoxide scavenging activity. All the compounds showed strong antioxidant capacity in all methods. In particular, fukugetin, a biflavonoid composed of the monomers naringenin and luteolin, showed highest antioxidant capacity among the compounds tested. The values were comparable to those of known antioxidants. In the DPPH and ABTS assays, the luteolin structure of fukugetin appeared to contribute to its antioxidant capacity. In the ORAC assay, the high antioxidant capacity of fukugetin resulted from the additive effect of naringenin and luteolin structures. Fukugetin also showed antibacterial capacity against some gram-positive bacteria. The minimum inhibitory concentration estimated by disk diffusion method was 0.125－1mg/mℓ, which is equivalent to known flavonoids such as kaempferol or quercetin. Our results showed the potential of fukugetin not only as an antioxidant but also as an antibacterial agent.