| Garcinia xanthochymus is a traditional Dai medicine native to the south and southwest of Yunnan Province, P. R. China which can grow up to 10-20 m. It is widely used as a traditional medicine for dispelling worms, clearing away fire and removing food toxin. Previous phytochemical studies of the leaves, seeds, fruits, twig bark, and wood have demonstrated the presence of benzophenones, flavonoids, triterpenes, and xanthones. Since most xanthones have phenolic functional groups on a linear tricyclic ring, they often exhibit a wide range of biological and pharmacological activities, such as antioxidative, antileukaemic, antitumour, antiulcer, antimicrobial, antihepatotoxic, and CNS depressant activities.In the course of our ongoing research project on bioactive natural products from G. xanthochymus, an EtOAc-soluble partition of the EtOH extract of the bark of G. xanthochymus was found to have significant antioxidant activity (IC50, 4.6μg/mL) by DPPH scavenging bioassay in our preliminary test. This prompted us to perform a detailed bioassay-guided isolation on this palnt, which led to the isolation of 13 new xanthones, including 28 known compounds. Thirteen new compounds were named as Garcinenone H (12), Garcinenone I (13), Garcinenone J (14), Garcinenone K (22), Garcinenone A (25), Garcinenone B (31), Garcinenone C (32), Garcinenone E (33), Garcinenone G (34), Garcinenone D (35), bigarcinenone A (38), bigarcinenone B (39), Garcinenone F (40). Other twenty-eight compounds were identified as: 1, 7-dihydroxy -xanthone (1), 1,4,5-trihydroxyxanthone (2), 1,3,6,7-tetrahydroxyxanthone (3), 1, 3,7- trihydroxyxanthone (4), 2,5-dihydroxy-1-methoxyxanthone (5), 1,5-dihydroxy-3- methoxyxanthone (6), 1,2-dihydroxy-5-methoxyxanthone (7), 1,3-dimethoxy-5-hydroxy xanthone (8), 1,2-dimethoxy-5-hydroxyxanthone (9), 1,3,5,7-tetrahydroxyxanhone (10), 1,5,7-trihydroxy-3-methoxyxanthone (11), 3,6,-dihydroxy-1,8-dimethoxyxanthone (15), 1,2-dihydroxy-6,8-dimethoxyxanthone (16), 2,6-dihydroxy-1,5-dimethoxyxanthone (17), 1,2-dihydroxy-5,6-dimethoxyxanthone (18), 6-dihydroxy-1,2,5-trimethoxyxanthone (19), 1,4,6-trihydroxy-5-methoxy-7-(3-methyl-4-buten1)xanthone (20), symphoxanthone (21), 12b-hydroxy-des-D-garcigerrin A (23), jacareubin (24), subeliptenone B (26), Toxyloxanthone-D (27), 1,4,5,6-tetrahydroxy-7,8-di(3-methylbut-2-enyl)xanthone (28), 7-Prenyljacareubin (29), 1,5,6-trihydroxy-6′,6′-dimethyl-2H-pyrano(2′,3′:3,4)-2-(3- methylbut-2-enyl)xanthone (30), 1,3,5,6-tetrahydroxy-4,7,8-tri(3-methyl-2-butenyl) xanthone (36), garciniaxanthone E (37), apigenin (41). Compounds 2~6, 8~11, 15~21, 23, 24, 26~30, 36, 37, and 41 were isolated from this plant for the first time.8 extracts of Garcinia xanthochymus were screened for their photoactivated antimicrobial activities against 4 bacterial strains by paper disc diffusion method. It was found that the extracts of root showed stronger antibacterial activities than that of bark, but had lower light-mediated activities than that of bark. EtOAc extracts of Garcinia xanthochymus displayed moderate photoactivated antimicrobial activities on two bacterial strains.The antioxidant activities of 4 extracts and 22 compounds from the bark of Garcinia xanthochymus was determined by using DPPH free radical scavenging method. The experimental results indicated that EtOAc extract of the bark had the strongest antioxidant activities, and compounds 2,18,20,21,23～26,31,33～37 showed stronger antioxidant activities than that of the well-known synthetic antioxidant butylated hydroxytoluene (BHT, IC50 = 20.0μM).
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