Anti-HIV-1 integrase diterpenoids from Dichrocephala benthamii

Five new clerodane diterpenoid dichrocephnoids A-E (1,2, 6-8) together with three known analogues were isolated from the whole herb of Dichrocephala benthamii C.B. Clarke. Their structures were elucidated on the basis of spectroscopic analyses (UV, IR, MS, 1D and 2D NMR). The relative configurations of the new compounds were established by NOESY correlations, and the absolute configuration of 1 was determined on the basis of CD methods. Dichrocephnoid A (1) possesses a very rare pentacyclic ring system with highly oxygenated functionalities. All of the isolated compounds exhibited inhibitory activity against HIV-1 integrase, however, dichrocephnoid C (6) showed the most promising inhibition of the enzyme with IC50 value of 12.35 +/- 1.27 mu M. (C) 2015 Phytochemical Society of Europe. Published by Elsevier B.V. All rights reserved.