Five undescribed aryltetralin lignans with cytotoxic activities from the fruits of Cleistanthus eberhardtii.

Five undescribed lignans, cleiseberharnins A-D (1-4), cleiseberharside A (5) were isolated from the fruits of Cleistanthus eberhartii (Phyllanthaceae), together with six known aryltetralin lignans, cleistantoxin (6), picroburseranin (7), neocleistantoxin (8), 7-hydroxypicropolygamain (9), cleisindoside D (10), and cleisindoside A (11). Their structures and relative configurations were established by analysis of HRESIMS and NMR data, and quantum chemical calculations of J coupling constants. The absolute configurations of 1-5 were determined by analysis of their experimental CD spectra and comparison with calculated electronic circular dichroism (ECD) spectra. All compounds (1-11) were evaluated for their cytotoxicity against KB, MCF-7, HepG-2, and Lu-1 human cancer cell lines. Among the tested compounds, compounds 6 and 7 showed strong activity against KB, MCF7, HepG2 and Lu-1 cell lines with IC values in the range of 0.02-0.62 μM. Compound 1 showed activity against three cancer cell lines KB, HepG2, and Lu-1 with IC values of 6.98, 7.61 and 11.75 μM, respectively. Compound 2 exhibited a selective inhibition with moderate cytotoxicity against Lu-1 with IC value of 15.30 μM. Compounds 4, 5 and 9 showed moderate activity against the three cancer cell lines with IC values in the range of 8.73-19.70 μM.