Studies On The Antioxidant And Antibacterial Activities Of Three Ethno-medicines

Garcinia xanthochymus, Fissistigma polyanthum and Microcos paniculata L. are traditional Dai medicines which have been used to prepare herbal medicines for a long time. Previous phytochemical investigations revealed the presence of benzophenones, flavones, xanthones, triterpenes and alkaloids in these three plants; and it has been reported that they not only have anti-inflammatory and antiulcer activities, but also exert antitumour, antihepatotoxic and CNS depressant effects. While a limited number of reports concerning the antioxidant and antibacterial activities of them have appeared in the literature. The objective of this study was to elucidate the antioxidant and antibacterial activities of the 36 compounds isolated from Microcos paniculata L.,Fissistigma polyanthum and Garcinia xanthochymus.The antioxidant activities of the tested compounds were evaluated through three in vitro model systems, such as 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2'-azino- bis(3-ethylbenzothiazoline-6-sulfnate) (ABTS) and Co (Ⅱ) EDTA-induced luminol chemiluminescence by flow injection. Among them, the total antioxidant capacities of the antioxidants were assessed by the DPPH and TEAC test, and the scavenging activities of the antiodants towards Hydroxyl radical was measured by Co (Ⅱ) EDTA-induced luminol chemiluminescence by flow injection test. The results showed that Garcinia xanthochymus with strong antioxidant capacity can be expected as a promising natural antioxidant. Compounds 8 (garcinexanthone F) and 21 (garcinexanthone B) exhibited potent antioxidant activities in the DPPH and TEAC test with IC50 value of 7.95μg/mL and 7.35μg/mL, respectively; while Compounds 4(1, 3, 5, 6-tetrahydroxy-8-(3-methylbut-2-enyl)-xanthone; garcinexanthone C) and 20 (2,6-dihydroxy-1,5-dimethoxyxanthone) were the most effective hydroxyl radical scavengers with IC50 value of 0.33μg/mL and 0.10μg/mL in the chemiluminescence by flow injection test. Compared with Garcinia xanthochymus, Fissistigma polyanthum and Microcos paniculata L. showed moderate antioxidant effects, while compound 2 (epicatechin) isolated from Microcos paniculata L. displayed significant antioxidant activity which is similar to that of standard antioxidant ascorbic acid (VC) and therefore may be a promising natural antioxidant. Epicatechin exhibited powerful scavenging activities against DPPH and hydroxyl radicals with IC50 values of 2.83μg /mL and 0.18μg /mL, respectively, and the ABTS scavenging activity of 2 (TEAC = 1.38±0.05) was found to significantly higher than that of Trolox.The antibacterial activities and the MICs (minimal inhibitory concentration) of the tested compounds were determined through broth microdilution method. It was found that Garcinia xanthochymus exhibited strong antibacterial capacity. Compounds 5 (Symphoxanthone) and 14 (1,5,6,5′-tetrahydroxy-7,8–di(3-methyl-2-butenyl)-6′, 6′-di- methylpyrano(2′,3′:3,4) xanthone) showed effective inhibitory activities against three bacteria strains (S. aereus, B. subtilis and B. mucilaginosus). And obviously, the antibacterial activities of the tested compounds were more sensitive to C. tropicalis than C. albicans. The compounds 6 (Garcinenone D), 22 (Garcinexanthone E), 25 (2-methylbutyryl phloroglucinol), 29 (1,4-Dihydroxy-6′,6′-dimethylpyrano (2′,3′:5,6) xanthone), 30 (1-dihydroxy-4,5-methoxyxanthone) showed the strongest activities against C. albicans with MIC value of 31.25μg/mL, and both the MIC value of compounds 14 (1,5,6,5′-tetrahydroxy-7,8–di(3-methyl-2-butenyl)-6′, 6′-dimethylpyra- no(2′,3′:3,4) xanthone) and 18(Subelliptenone H) against C. tropicalis was 3.91μg/mL.