Bioactive Saponins and Glycosides. IV. Four Methyl-Migrated 16,17-seco-Dammarane Triterpene Glycosides from Chinese Natural Medicine, Hoveniae Semen Seu Fructus, the Seeds and Fruit of Hovenia dulcis THUNB.: Absolute Stereostructures and Inhibitory Activity on Histamine Release of Hovenidulciosides A1, A2, B1, and B2.

Four bioactive methyl-migrated 16,17-seco-dammarane type triterpene glycosides called hovenidulciosides A1, A2, B1, and B2 were isolated from a Chinese natural medicine, Hoveniae Semen Seu Fructus, the seeds and fruit of Hovenia dulcis THUNB. (Rhamnaceae) together with hoduloside III and (+)-gallocatechin. The absolute stereostructures of hovenidulciosides A1, A2, B1, and B2 have been elucidated by chemical and physicochemical evidence. All were found to inhibit the histamine release from rat peritoneal exudate cells induced by compound 48/80 and calcium ionophore A-23187.