Further terpenoids from Vitex negundo L. growing in Vietnam

A new labdane-type diterpenoid, 9-epi-vitexnegundin (1), was isolated from the leaves of Vitex negundo L. together with seven known compounds: 8,13-diepi-manoyl oxide (2), 8-epi-sclareol (3), sclareol (4), 9,13-epoxy-labd-14-ene (5), vitedoin B (6), argyol (7), and predicularis-lactone (8). The chemical structures were elucidated by analysis of spectroscopic data and comparison with published NMR data. The DP4 + probability method was used to determine the relative stereochemistry of 9-epi-vitexnegundin. Complete NMR assignments of compound 2 were determined, revising the previously-reported NMR data for this compound. The stereochemistry of 9,13-epoxy-labd-14-ene (5) was elucidated for the first time, based on NOESY correlations. All isolated compounds 1-8 were evaluated for cytotoxicity against the K562 cell line, as were vitexnegundin (9), vitexilactone (10), vitetrifolin D (11), 13-hydroxy-5(10), 14-halimadien-6-one (12), artemetin (13), vitexicarpin (14), penduletin (15). Compounds 10-15 exhibited moderate cytotoxicity, with IC50 values in the range 15.7-79.8 04. (C) 2021 The Author(s). Published by Elsevier B.V. on behalf of King Saud University.