Abstract
Four new cytotoxic cleistanthane diterpenoids, named pyranthanols A-B (1-2) and pyranthanones A (3-4), were isolated from Vellozia pyrantha A.A.Conc resin, along with four known compounds (5-8). These compounds show varying degrees of oxidation with hydroxyl and carbonyl groups at different positions of the cleistanthane core skeleton. Their structures were proposed after careful analysis of (1)H and (13)C NMR, HMBC, HMQC, and COSY and NOESY 1D data and comparison with the literature. Pyranthanol B (2) and pyranthanones A-B (3-4) were active against a lung carcinoma cell line (H-1299) with IC(50) values varying from 27.57 ± 6.89 to 99.96 ± 22.64 μM, whereas pyranthanol B (2) and pyranthanone B (4) were active against a human liver carcinoma cell line (HepG2) with IC(50) values of 36.21 ± 11.97 and 43.63 ± 25.53 μM, respectively. Pyranthanol B (2) and pyranthanone A (3) were also toxic against a normal lung cell line (MRC-5) with IC(50) values of 49.99 ± 19.98 and 43.63 ± 43.63 ± 20.25 μM, respectively. The moderate activity observed may suggest these compounds as potential candidates for drug development against carcinoma cell lines.