RXRα Transcriptional Inhibitory Constituents From The Stems Of Calophyllum Membranaceum

In this paper,under the guidance of the RXRa transcription assay,32 compounds were obtained from the 60%ethanol extract of the stems of Calophyllum membranaceum Gardn.et Champ.through various chromatographic techniques,such as Diaion HP20 macroporous adsorption resin column chromatography(CC),silica gel CC,Sephadex LH-20 CC,ODS CC and PHPLC.On the basis of extensive analyses of physico-chemical properties and spectroscopic evidences,their structures were identified as calopolyanic acid methyl ester(1),isopinetoric acid methyl ester(2),membranacic acid(3),apetalic acid(4),pinetoric acid III(5),isopinetoric acid Ⅲ(6),calophylixanthone A(7),calophylixanthone B(8),4-hydroxyxanthone(9),2,7-dihydroxyxanthone(10),2,5-dihydroxyxanthone(11),7-hydroxy-1-methoxyxanthone(12),2-hydroxy-1-methoxyxanthone(13),1,3,5-trihydroxyxanthone(14),1,2-methoxyxanthone(15),2-hydroxy-1,8-dimethoxyxanthone(16),7-hydroxy-1,2-dimethoxyxanthone(17),1,2,8-trimethoxyxanthone(18),1,7-dihydroxy-3,4,8-trimethoxyxanthone(19),catechin(20),epicatechin(21),7,4’-dihydroxyisoflavone(22),puerarin(23),nyasol(24),3"-hydroxy-4"-methoxy-4"-dehydroxynyasol(25),broussonin B(26),phillygenin(27),6’-O-vanilloyltachioside(28),4-hydroxy-2-methoxyphenyl-6-O-syringoyl-β-D-glucopyranoside(29),calophymembranside C(30),ent-4(15)-eudesmene-1β,6α-diol(31)and protocatechuic methyl ester(32).Among them,6 compounds(1-3,7,8,30)are new compounds,and 6 compounds(24-26,28-29,31)are reported from the Calophyllum genus for the first time.25 compounds(1-6,9-13,15-16,18-22,24-27,30-32)were evaluated for their effects on RXRa transcriptional activity using a reporter gene assay.The results showed that 8 compounds(11,13,18-20,24,2 7,30)possessed the transcriptional inhibitory activity of RXRα,which was concentration-dependent.C-glycoside showed its RXRa transcriptional inhibitory activity for the first time.Molecular docking modeling was carried out using the CDOCKER method to dock active compounds(11,13,18-20,24,27,30)into the ligand-binding pocket of RXRa to further verify the RXRa transcriptional inhibitory activity.Compounds 11,13,18-20 and 30 could form Pi-Pi interactions with Phe313,and both compounds 24 and 27 could form Pi-Pi interactions with Leu309 and Ala272.Compound 11 could form hydrophobic interactions with eight residues,compounds 13 and 19 could form hydrophobic interactions with four residues,compounds 18 and 30 could form hydrophobic interactions with nine residues,compound 20 could form hydrophobic interactions with seven residues,and compounds 24 and 27 could form hydrophobic interactions with six residues.