Anti-neuroinflammatory diterpenoids from the endangered conifer Podocarpus imbricatus

Ten diterpenoids including three new abietanes (1–3) were isolated from the twigs and needles of Podocarpus imbricatus, an endangered conifer growing in a Cantonese garden. The new structures were established by means of spectroscopic methods. Among the isolates, 3β-hydroxy-abieta-8,11,13-trien-7-one (5), decandrin G (6), and 7,15-pimaradien-18-oic acid (8) showed significant anti-neuroinflammatory activities by inhibiting the overproduction of nitric oxide (NO) in lipopolysaccharide (LPS)-stimulated murine BV-2 microglial cells, with IC₅₀ values of 3.7, 11.1, and 4.5 μM, respectively.