Anti‐Neuroinflammatory Labdane Diterpenoids From the Rhizomes of <i>Alpinia zerumbet</i>

Alpinia zerumbet, commonly known as shell ginger, is a plant of significant ornamental and medicinal value. In the present study, nine labdane-type diterpenoids, including four novel (1-4) and five known (5-9), were isolated and identified from the rhizomes of A. zerumbet. Anti-neuroinflammatory activities of the isolated labdane-type diterpenoids were evaluated in lipopolysaccharide (LPS)-stimulated microglia BV2 cells. Compounds 3, 5, 6, and 8 could significantly inhibit the production of nitric oxide (NO) in LPS-stimulated BV2 cells. Among them, the IC₅₀ values of compounds 5 and 8 were 26.14 ± 1.62 and 17.29 ± 6.28 µM, which were lower than that of the positive control, minocycline (IC₅₀ = 30.26 ± 1.99 µM).