Cytotoxic 24-nor-ursane-type triterpenoids from the twigs of Mostuea hirsuta

Abstract

Abstract Two new 24-nor-ursane-type triterpenoids, 2α,3β,19α-trihydroxy-24-norurs-4(23),12-dien-28-oic acid (1) and 3β-acetoxy-2α,19α-dihydroxy-24-norurs-4(23),12-dien-28-oic acid (2), along with 15 known compounds were isolated from the methanol extract of the twigs of Mostuea hirsuta. While 2-hydroxymethylbenzamide (13) was isolated for the first time from the natural source, compounds 3–12 are reported here for the first time from the genus Mostuea. Their structures were elucidated by means of spectroscopic analyses including 1D- and 2D-NMR spectroscopy, high-resolution mass spectrometric data as well as comparison with data from the literature. Compounds 1, 2, 4–9 and 13 were tested against bacteria, fungi and plant pathogen oomycetes by the paper disk agar diffusion assay resulting in missing to low activities corresponding with minimum inhibitory concentrations (MICs) > 1 mg mL–1. However, the respective compounds 1, 2, 8, 9 and 13 exhibited moderate cytotoxic activity against the human Caucasian prostate adenocarcinoma cell line PC-3, with IC50 10.6–16.5 μm compared to the standard doxorubicin with IC50 0.9 μm.