New Oleanane-Type Triterpene Saponins, Goyasaponins I, II, and III, from the Fresh Fruit of Japanese Momordica charantia L

(Japanese name “Tsurureishi”) is cultivated as a vegetable in Asian countries. In Chinese, Indian Ayurvedic, and Indonesian Jamu traditional medicines, the fruit of this plant has been used as a bitter stomachic, a laxative, an antidiabetic, and an anthelmintic for children. Recently, the alcoholic extract from the fruit of M. charantia originated in Sri Lanka was reported to inhibit the increase of serum glucose in glucose-loaded rats. As chemical constituents of the fruit, many cucurbitane-type triterpene glycosides were reported, but the constituents responsible for the inhibition of glucose absorption have not been identified. In the course of our studies on the bioactive constituents of medicinal foodstuffs, we have also characterized many triterpene glycosides from the fruit of M. charantia originated in Japan, Thailand, Indonesia, India, and Sri Lanka. In this paper, we present the isolation and structure elucidation of goyaglycosides-a (1), -b (2), -c (3), -d (4), -e (5), -f (6), -g (7), and -h (8) and goyasaponins I (9), II (10), and III (11) from the fresh fruit of Japanese M. charantia, which is commonly called “nigauri” or “goya”. The cucurbitaneand oleanene-type triterpene glycosides of the fresh fruit of Japanese M. charantia were separated by the procedures shown in Chart 1. The methanolic extract obtained from the fresh fruit of M. charantia was partitioned into an ethyl acetate and a water mixture to give an ethyl acetate extract and an aqueous phase. The aqueous phase was extracted with 1-butanol to furnish a 1-butanol extract and an aqueous extract. The 1-butanol extract was subjected to normaland reversed-phase silica gel column chromatography and finally HPLC to give goyaglycosides-a (1), -b (2), -c (3), -d (4), -e (5), -f (6), -g (7), and -h (8), goyasaponins I (9), II (10), and III (11), and momordicosides A (12), C (13), F1 3c) (14), I (15), and K (16). Structures of Cucurbitane-Type Triterpene Glycosides (1—8) Goyaglycoside-a (1) was obtained as a white pow-