Structurally diverse abietane diterpenoids from the whole plants of Salvia przewalskii Maxim. With anti-inflammatory activity.

Using bioactivity guidance, eight previously undescribed abietane diterpenoids (1-8), were isolated from the whole plants of Salvia przewalskii Maxim. along with seven known analogues (9-15). Their structures were elucidated by extensive spectroscopic analyses, quantum chemical calculations, and single crystal X-ray diffraction. Among them, compound 1, an abietane diterpenoid bearing unique C-20 m-cymen-8-ol monoterpenoid moiety, was the first example of the adduct between a monocyclic monoterpenoid and an abietane diterpenoid connected by ester bond within the Salvia genus. The plausible biosynthetic pathways of 1-8 were proposed. All isolates were tested for their inhibitory activity towards the LPS-induced NO production in RAW 264.7 cells. Compounds 3, 5, 6 and 9 significantly inhibited nitric oxide (NO) production in RAW264.7 cells, which also could suppress the release of pro-inflammatory factors (TNF-α, IL-1β and IL-6). The key structure-activity relationships of these abietane-type diterpenes for anti-inflammatory effects have been summarized.