Isolation and characterisation of sesquiterpene lactones from Schkuhria pinnata and their antibacterial and anti-inflammatory activities

Abstract

Schkuhria pinnata (Lam.) Kuntze ex Thell is used traditionally to treat a number of diseases linked with bacterial infections and inflammation such as eye infections, diarrhoea, diabetes and stomach problems. Despite these uses, there is still insufficient information on the isolation and evaluation of active compounds from this plant. Thus, the study was aimed at identification and characterisation of the antibacterial and anti-inflammatory active extracts of Schkuhria pinnata. Antibacterial activity was evaluated by the micro-broth dilution method. Bioassay-guided fractionation aided the isolation of four compounds from the dichloromethane extracts. The structures of the isolated compounds were elucidated using NMR data. The compounds were further tested for antibacterial, cytotoxic and anti-inflammatory activity using serial dilutions. Four sesquiterpene lactones were identified, 6α-[4′,5′-dihydroxytigloyloxy]-inuviscolide 1 and, 3-desacetyl-3-isovaleroyleucannabinolide 2, eucannabinolide 3 and 6α-[4′,5′-dihydroxytigloyloxy]-isoinuviscolide 4. These compounds exhibited less antibacterial activity as compared to the crude extracts and fractions. Anti-inflammatory and cytotoxic activities were also demonstrated. The activities reported for the extracts support the traditional uses of this plant for treatment of infections linked with microorganisms and inflammatory related disorders.