Stilbenes from the tubers of Bletilla striata with potential anti-neuroinflammatory activity.

Neuroinflammation are involved in the pathogenesis of many neurodegenerative disorders. In our screening of natural effective neuroinflammatory inhibitors from natural products, stilbenes, such as resveratrol and its analogues, have received considerable attention over the last several decades as anti-neuroinflammatory agents. Then, Bletilla striata attracted our attention due to its abundant stilbenes portion, PE fraction. So, three new stilbenes: dusuanlansin E1 (23a), dusuanlansin E2 (23b), 3-hydroxy-5-methoxybibenzyl-3'-O-β-d-glucopyranoside (27), and 30 known stilbene compounds were isolated from B. striata. These structures of the compounds were established on the basis of extensive spectroscopic analysis including 1D and 2D NMR and circular dichroism (CD) data. Furthermore, all the isolated components were tested in vitro for their inhibitory effects on the nitric oxide generation in LPS-stimulated BV2 cells. As a result, compounds 2, 5, 6, 16, 17 can greatly inhibit the NO production without cytotoxicity. In addition, SARs between stilbenes and anti-neuroinflammation effects were discussed briefly. In conclusion, stilbenes were characteristic constituents of the tubers of B. striata with potential anti- neuroinflammatory effects.