Norquandrangularic acid D, a new trinorcycloartane isolated from the leaves of Combretum quadrangulare

Phytochemical investigation on the leaves of Combretum quadrangulare growing in Vietnam afforded a new trinorcycloartane triterpenoid, norquandrangularic acid D (1), along with three known compounds, betulinic acid (2), luteolin (3), and apigenin (4). Their structures were elucidated using spectroscopic methods and comparison was made with reports in the literature. Compounds 1 and 3 were evaluated for α-glucosidase inhibition. Compound 3 showed significant activity, with an IC₅₀ value of 11.39 µM, (acarbose, used as a positive control, had an IC₅₀ of 367 µM).