Natural nitric oxide (NO) inhibitors from Aristolochia mollissima

Abstract

Six new sesquiterpenoids, aristomollins A–F (1–6), and 24 known analogues (7–30) were isolated from the leaves and stems of Aristolochia mollissima. Their structures were elucidated by spectroscopic analysis, and the absolute configurations of compounds 2–5 were determined by the chemical correlations and quantum chemical ECD calculations. Compound 1 represented an unprecedented 5,6-seco-4,5-cyclohumulane skeleton. All the compounds were examined for their inhibitory effects on the nitric oxide (NO) production induced by lipopolysaccharide (LPS) in BV-2 microglial cells, and compounds 4, 9, 28, and 30 exhibited pronounced inhibition of NO production with IC₅₀ values in the range of 5.7–9.9 μM, being more active than the positive control, quercetin (IC₅₀ = 15.7 μM).