AbstractThe alcoholic extract of Gymnosporia trilocularis Hay. (Celastraceae) was found to exhibit antitumor activities against P388 lymphocytic leukemia and KB cell culture systems. From this extract β‐amyrin (1), β‐sitosterol (2) and its monoglucoside (6), stigmasterol (3) and its monoglucoside (7), campesterol (4) and its monoglucoside (8), maniladiol (5), dulcitol (9) and six yet unidentified principles (10–15) were isolated. The stereochemistry of C‐16‐OH of maniladiol (5) was confirmed spectroscopically by 1H nmr to be equatorial. Of all the isolated compounds, the mixture of three steroid monoglucosides (6:7:8=28:1.1:1) exhibited cytotoxicity (ED50=2.6×100 mcg/ml) and 5 showed only marginal effect (ED50=2.1×101 mcg/ml) in KB test system.