Hopeachinols E-K, novel oligostilbenoids from the stem bark of Hopea chinensis

Five new stilbenolignans, hopeachinols E-I (1-5), and two new stilbenoids, hopeachinols J and K (6 and 7), together with the known resveratrol trimer, vaticanol A (8), were isolated from the stem bark of Hopea chinensis. The structures and relative configurations of these natural products were elucidated by using spectroscopic and spectrometric methods. The (8R) absolute configuration of 1 was assigned by using the modified Mosher ester method. Hopeachinols E-I (1-5) possess unprecedented stilbenolignan skeletons, in which a stilbene trimer is linked with a phenylpropanoid unit through a pyran bridge. Hopeachinols J and K (6 and 7) have new skeletons in which a stilbene trimer is connected by an additional two-carbon unit through a furan moiety. An evaluation of the cytotoxicities against HCT116, MDA-MB-231, SMMC-7721, and HepG2 cell lines of the new hopeachinols showed that 1, 2, 4, and 6 have moderate activities with IC₅₀ values in the 10.39-18.72 μM range.