Flavaglines with anti-neuroinflammatory activity from Aglaia edulis (Roxb.) Wall. and structure revision of related flavaglines

Eight cyclopenta[b]benzofurans (1, 2, 4, and 5-9) and eight cyclopenta[bc]benzopyrans (3, 10–16), including a revised (4) and three undescribed compounds (1–3), were isolated from the twigs and leaves of Aglaia edulis (Roxb.) Wall. Their structures were determined by a combination of spectral analysis in conjunction with NMR and ECD calculations. Moreover, based on the findings from ¹³C NMR calculations and DP4+ statistical analysis, an empirical guideline was established to differentiate the structures of cyclopenta[bc]benzopyrans and cyclopenta[b]benzofurans by aggregating chemical shift data from known compounds. This guideline facilitated the proposal of structural revisions for three previously reported analogs (R-1, R-2, R-3). Biological assay indicated that cyclopenta[b]benzofuran flavalines (2, and 4–8) could significantly inhibit NO production in LPS-induced BV-2 cells with IC₅₀ values from 0.002 to 0.05 μM.