Anti-inflammatory abietane-type diterpenoids from the roots of Salvia przewalskii

Fourteen diterpenes were isolated and purified from the roots of Salvia przewalskii, including eight previously unreported abietane analogues (compounds 1-4, 9, 10a, 11a, and 11b), five known ones (5-8 and 10b), and one icetexane analogue (12). The structures were determined through spectroscopic data interpretation, optical rotations, calculated NMR-DP4⁺ analysis, and ECD. Compounds 1-8 belong to a class of abietane derivatives containing a [5, 5]-oxospirolactone moiety. The research explored the mechanism behind the prevalence of 16β-type [5, 5]-oxospirolactone as the major component in the inseparable mixtures, shedding light on the proposed biosynthetic pathway of these compounds. Consistent with experimental findings, it was revealed that the 16β-type [5, 5]-oxospirolactone was shown to exhibit significantly lower free energy of formation compared to the 16α-product. Additionally, all compounds were evaluated for their ability to inhibit NO production in LPS-induced RAW 264.7 macrophages. Compounds 1, 2, and 11a demonstrated promising bioactive properties in terms of inhibiting NO release.