| In our investigation on the chemical constituents of Cratoxylum. formosum ssp. pruniflorum,47 compounds were obtained from the 60% ethanol extract of the stems of this plant through various chromatographic techniques. On the basis of physico-chemical properties and intensive spectroscopic analyses, their structures were elucidated as 1,7-dihydroxyxanthone (1), 1,5-dihydroxy-6-methoxyxanthone (2), 1,7-dihydroxy-8-methoxyxanthone (3), 1,6-dihydroxy-7,8-dimethoxyxanthone (4), 1,3,7-trihydroxyxanthone (5), 1,3,6-trihydroxy-5-methoxyxanthone (6), 1,3,6-trihydroxy-7-methoxyxanthone (7),1,4,7-trihydroxyxanthone (8), 1,4,8-trihydroxyxanthone (9)*, 1,4,7-trihydroxy-8-methoxy-xanthone (10), 1,7-dihydroxy-4-methoxyxanthone (11), 1,6-dihydroxy-4,7-dimethoxyxanthone (12)*, 1,2-dimethoxy-3,7,8-trihydroxyxanthone (13)*, 1,3,7-trihydroxy-2-(3-methylbut-2-enyl)xanthone (14), 1,3,7-trihydroxy-2,4-bis(3-methylbut-2-enyl) xanthone (15), cudratricusxanthone E (16), y-mangostin (17), dulcisxanthone B (18), a-mangostin (19),β-mangostin (20), 1,6,7-trihydroxy-2-(3-methylbut-2-enyl)-3-methoxy-8-(3-hydroxy-3-methylbutyl)-xanthone (21)*,1,3,5-trihydroxy-4-(3,7-dimethylocta-2,6-dienyl)xanthone (22), 1,3,7-trihydroxy-2-(3-methylbut-2-enyl)-4-(3,7-dimethylocta-2,6-dienyl)xanthone (23),1,3,6,7-tetrahydroxy-2-(3-methyl-2-butenyl)-4-(3,7-dimethylcota-2,6-dienyl)-xanthone (24)*, cochinchinone B (25), 1,3,7-trihydroxy-2-(3-methyl-2-butenyl)-8-(3,7-dimethylcota-2,6-dienyl)xanthone (26)*, isocudraniaxanthone A(27), isocudraniaxanthone B (28),5-O-methyl-2-deprenylrheediaxanthone B (29), 1,5-dihydroxy-4’,4’-dimethyl-6’-hydroxy-4,5-dihydropyrano(2’,3’:3,4)xanthone (30), xanthone V1 (31), garcinone B (32), cratoxylumxanthone A (33), cochinchinone J (34), cochinchinone G (35), 1,7-dihydroxy-2-(3-methylbut-2-enyl)-3-O-(3,7-dimethylocta-2,6-dienyl)xanthone (36)*,2-hydroxy-1,4-dimethoxy-7-O-β-D-glucopyranosylxanthone (37)*,7-hydroxy-1,4-dimethoxy-2-O-β-D-glucopyranosyl xanthone (38)*,4-O-β-D-gluco-pyranosyl-2’,3,6’-trihydroxybenzophone (39)*, (+)-isolariciresinol-9-O-β-D-glucopyranoside (40), (+)-5-methoxyisolariciresinol- 9-O-β-D-glucopyranoside (41), (+)-lyoniresinol-9-O-β-D-glucopyranoside (42), (+)-catechin (43), (-)-epicatechin (44), procyanidin B2 (45), luteolin (46), isoquertin (47), respectively. Among them, ten compounds (9,12,13,21,24,26,36-39) were new compounds,11 compounds (1,4,7,14,16,27-29,31,32,47) were isolated for the first time from the genus Cratoxylum.Fourty two compounds were evaluated for their effects on RXRa transcriptional activity using a reporter gene assay. The results showed that 15 compounds (3,7,10, 11,16,18,21,24,25,27-31,39) possessed the transcriptional inhibitory activities of RXRa in various degrees.Preparatory structure-activity relationship of bioactive xanthones showed that the xanthone with a penta-or hexa-oxygen heterocycles attached to C-3 and C-4 positions in its structure possessed more potent RXRa transcriptional inhibitory activity than the others. In order to prove this hypothesis, ten xanthone derivatives were synthesized, and then evaluated for their RXRa transcriptional inhibitory activities. Some of them showed potent activities, which possessed a penta-or a hexa-oxygen heterocycles at C-3 and C-4 positions in their stucture.Nevertheless,32 compounds were tested for their regulation of TR3 mRNA expression. As showed in the results, 11 compounds (2～3,5～6,8,16～17,21,26,28, 29) induced expression of TR3 mRNA in H460 lung cancer cells at 1μmol/L concentration.According to the results, several xanthones could not only induce the expression of TR3 mRNA, but also inhibit the RXRa transcriptional activity. However, more experiments are needed to ascertain whether these xanthones exert their apoptosis-inducing effects by regulating RXR/TR3 heterodimer. |
PDF Full Text Request