Title: An examination of the Rubiaceae of Rong Kong. VII. The occurrence of triterpenoids, steroids, and triterpenoid saponins
Abstract:Earlier papers of this series have reported the work on eleven species of the Hong Kong Rubiaceae, two of which have been shom1a2 to contain triterpenoids occurring both in the free state and as sapog...Earlier papers of this series have reported the work on eleven species of the Hong Kong Rubiaceae, two of which have been shom1a2 to contain triterpenoids occurring both in the free state and as sapogenins, while another six have been proved to yield free triterpenoids.Either a phytosterol or a phytosterol mixture has been isolated from each of the plants investigated.We report here further work on three more species of the family.Examination of the leaves of Ixora chinensis Lam.revealed the presence of the triterpenoids lupeol and betulin, and the sterols p-sitosterol and stigmasterol.Investigations on two Randia species, R. canthioides Champ.ex Benth.and R. sinensis (Lour.)Schult., led to the isolation of stigmasterol from the stems of the former and ,&sitosterol from the leaves and sten~s of both species.I n the leaves of R. canthioides, cincholic acid has been found to occur both in the free state and as sapogenin, the sugar moiety of which is 6-deoxy-D-glucose.The stems of R. sinensis have been shown to contain a saponin which on hydrolysis yielded mesembryanthemoidigenic acid and D-glucose.The occurrence of cincholic acid in sapogenin mixtures has been reported from three plants of the Rubiaceae family,?-3 but this is the first isolation of it as a free triterpenoid and as a pure sapogenin.The only previous report on mesembryanthemoidigenic acid was made by Tursch et al.4 in 1965.They isolated the new acid as a sapogenin from Rhipsalis mesembryanthemoides Steud., and determined its structure to be 3,B,29-dihydroxyolean-12-en-28-oic acid.The mass spectrum of methyl mesembryanthemoidigenate showed prominent ions a t m/e 486, 7.5% (M+); 455, 13% (M+-CH20H); 427, 2.5% (M+-COOCH,); 426, 4% (Mt-COOCH,-H); 278, 33.6% (retro-Diels-Alder fragment a); 265, 6.5% (b); 247, 100% (a-CH,OH and b-H,O); 219, 14.3% (a-COOCH,); 218, 14.9% (a-COOCH,--H); 207, 24.9% (c); 205, 7.5% (d); 201, 43.5% (a-COOCH, -H20).It is noteworthy that the base peak is the ion mle 247, and not the expected ion m/e 219, which is formed by loss of the angular methoxycarbonyl group at C28Read More