New Cleistanthane Diterpenoids from Vellozia pyrantha A.A.Conc and Their Cytotoxic Activity.

Abstract

Four new cytotoxic cleistanthane diterpenoids, named pyranthanols A<b>-</b>B (<b>1-2</b>) and pyranthanones A (<b>3-4</b>), were isolated from Vellozia pyrantha A.A.Conc resin, along with four known compounds (<b>5-8</b>). 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 ¹H and ¹³C NMR, HMBC, HMQC, and COSY and NOESY 1D data and comparison with the literature. Pyranthanol B (<b>2</b>) and pyranthanones A-B (<b>3-4</b>) were active against a lung carcinoma cell line (H-1299) with IC₅₀ values varying from 27.57 ± 6.89 to 99.96 ± 22.64 μM, whereas pyranthanol B (<b>2</b>) and pyranthanone B (<b>4</b>) were active against a human liver carcinoma cell line (HepG2) with IC₅₀ values of 36.21 ± 11.97 and 43.63 ± 25.53 μM, respectively. Pyranthanol B (<b>2</b>) and pyranthanone A (<b>3</b>) were also toxic against a normal lung cell line (MRC-5) with IC₅₀ 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.