Oroxindols A and B, two novel secoabietane diterpenoids from Oroxylum indicum

Abstract Two novel secoabietane diterpenoids, oroxindols A (1) and B (2), along with two known flavones oroxylin A (3) and hispidulin (4) were isolated from the stem bark of Oroxylum indicum. Their structures were elucidated by extensive analysis of the 1D and 2D NMR as well as HR-ESI-QTOF mass spectra. Noteworthily, the isolation of compounds 1 and 2 represents the first case of 11β,13;12,13-diepoxy-12,13-secoabietane-type diterpene obtaining reported to date. In addition, compound 3 exhibited significant inhibitory effects on nitric oxide (NO) production in LPS-stimulated BV2 microglial cell line, with an IC50 value of 21.5 ± 1.1 μM.