Triplinones A-H: Anti-Inflammatory Arylalkenyl α,β-Unsaturated-δ-Lactones Isolated from the Leaves of Australian Rainforest Plant Cryptocarya triplinervis (Lauraceae)

Our ongoing exploration of Australian rainforest plants for the biodiscovery of anti-inflammatory agents led to the isolation and structural elucidation of eight new arylalkenyl α,β-unsaturated-δ-lactones, triplinones A-H (1-8), from the leaves of the Australian rainforest plant Cryptocarya triplinervis B. Hyland (Lauraceae). The chemical structures of these compounds were established by NMR spectroscopic data analysis, while their relative and absolute configurations were established using a combination of Mosher ester analysis utilizing both Riguera’s and Kishi’s methods, ECD experiments, and X-ray crystallography analysis. Compounds 1-8 exhibited good inhibitory activities toward nitric oxide (NO) production in lipopolysaccharide (LPS) and interferon (IFN)-γ induced RAW 264.7 macrophages, in particular compounds 1-3 and 5, with IC₅₀ values of 7.3 ± 0.5, 6.0 ± 0.3, 5.6 ± 0.3, and 5.4 ± 2.5 μM, respectively.