Structures and biological activities of the triterpenoids and sesquiterpenoids from Alisma orientale

Abstract

Sixteen triterpenoids and nine sesquiterpenoids were isolated from the rhizome of Alisma orientale. Structures of 16-oxo-11-anhydroalisol A 24-acetate, 13β,17β-epoxy-24,25,26,27-tetranor-alisol A 23-oic acid, 1αH,5αH-guaia-6-ene-4β,10β-diol, and alisguaiaone were elucidated by comprehensive spectroscopic data analysis. The cytotoxic, antibacterial, antifungal, anti-inflammatory, and α-glucosidase inhibitory activities of isolated terpenoids were evaluated. Triterpenoids alisol A, alisol A 24-acetate, 25-O-ethylalisol A, 11-deoxyalisol A, alisol E 24-acetate, alisol G, alisol B 23-acetate and sesquiterpenoids 1αH,5αH-guaia-6-ene-4β,10β-diol, 10-hydroxy-7,10-epoxysalvialane exhibited cytotoxicities against the three tested human cancer cell lines with IC₅₀ values ranging from 11.5 ± 1.7 μM to 76.7 ± 1.4 μM. Triterpenoids alisol A, 25-O-ethylalisol A, 11-deoxyalisol A, alisol E 24-acetate, alisol G, and 25-anhydroalisol F showed antibacterial activities against the Gram-positive strains Bacillus subtilis and Staphylococcus aureus with MIC values of 12.5-100 μg/mL. Sesquiterpenoid 4β,10β-dihydroxy-1αH,5βH-guaia-6-ene exhibited antibacterial activity against B. subtilis with an MIC value of 50 μg/mL, and 10-hydroxy-7,10-epoxysalvialane exhibited activity against S. aureus with an MIC value of 100 μg/mL. Compounds 16-oxo-11-anhydroalisol A 24-acetate, alisol F, 25-anhydroalisol F, and alisguaiaone exhibited inhibitory effects on lipopolysaccharide-induced NO production in RAW 264.7 macrophage cells. None of the compounds showed obvious inhibitory activity against α-glucosidase.

Keywords: Alisma orientale; Alismataceae; Anti-inflammatory activity; Antibacterial activity; Cytotoxicity; Sesquiterpenoid; Triterpenoid.