Iridoid glycosides from Gmelina philippensis.

Six new iridoids, 6-O-alpha-L-(2"-O-, 3"-O-, 4"-O-tribenzoyl)rhamnopyranosylcatalpol, 6-O-alpha-L-(2"-O-, 3"-O-dibenzoyl, 4"-O-cis-p-coumaroyl)rhamnopyranosylcatalpol, 6-O-alpha-L-(2"-O-, 3"-O-dibenzoyl, 4"-O-trans-p-coumaroyl)rhamnopyranosylcatalpol, 6-O-alpha-L-(2"-O-benzoyl, 3"-O-trans-p-coumaroyl)rhamnopyranosylcatalpol, 6-O-alpha-L-(2"-O-, 3"-O-dibenzoyl)rhamnopyranosylcatalpol, and gmephiloside as well as five known monoacyl and diacyl rhamnopyranosylcatalpol derivatives were isolated from the aerial parts of Gmelina philippensis. Their structures were established by spectroscopic means. Additionally, the known iridoids catalpol, geniposidic acid, gardoside, and 8-epi-loganic acid were identified and quantified by GC and GC-MS. The taxonomic significance of rhamnopyranosylcatalpol derivatives and iridoid acids as chemical characters is discussed.