Two novel resveratrol dimers from Vatica albiramis: structural elucidation and UV-induced formation.

Two novel resveratrol dimers, vaticanols O (1) and P (2), were isolated from the bark and stem wood of Vatica albiramis (Dipterocarpaceae), a genus rich in highly oligomerized stilbenoids. Along with seven known constituents, their structures were elucidated by comprehensive spectroscopic analyses, including 1D and 2D NMR, HR-ESI-MS, and ECD measurements. Compound 1 possesses a rare fused ring skeleton comprising a 1,2-dihydrobenzo[1, 2-b:4,3-b'] difuran unit, while 2 features a 6,10b-dihydro-1H-anthra[1, 9-bc] furan skeleton with an additional C₁ unit. Absolute configurations were assigned from NOESY correlations and electronic circular dichroism (ECD) data, supported by molecular modeling. Importantly, both dimers can be generated from ( -)-(E)-ε-viniferin under UV irradiation, as verified by LC-ESI-QTOF-MS, providing experimental support for plausible non-enzymatic biosynthetic pathways. These UV-induced transformations, monitored by LC-ESI-QTOF-MS, represent the first report of photo-triggered structural diversification of ( -)-(E)-ε-viniferin.