New oxygenated sesquiterpenes from Bontia daphnoides L. leaves and in vitro evaluation of its antiviral and anti-inflammatory activity

Bontia is a monotypic genus containing Bontia daphnoides which is known as olive bush. It was used traditionally for the treatment of herpes, cough, colds, inflammation, ulcers and wounds. Therefore, in this study the anti-inflammatory and antiviral activities of the leaves extract and fractions were measured in vitro. Also phytochemical investigation of the non-polar fractions was done to identify the compounds responsible for activity. The anti-inflammatory activity was assessed by measuring the inhibition of superoxide anion generation and elastase release in fMLF/CB-induced human neutrophils. The antiviral activity was measured against Herpes simplex virus type 1 (HSV-1) and Hepatitis A virus (HAVH10). The dichloromethane fraction showed the most potent anti-inflammatory activity by inhibiting superoxide anion generation and elastase release with IC₅₀ 5.21and 6.72 μg/mL, respectively. It showed antiviral activity with EC₅₀ of 332 and 290 μg/mL for HSV-1 and HAVH10, respectively. The total extract showed a promising antiviral activity with EC₅₀ of 214 and 190 μg/mL against HSV-1 and HAVH10, respectively. Phytochemical investigation of the n-hexane fraction of B. daphnoides resulted in the isolation of three oxygenated sesquiterpenes; dehydroepingaione (1), 10,11-dehydromyoporone (2) and the newly isolated compound; 1,2,15 trihydro-1,15-dimethoxy-2, 3-dihydroxy-dehydrongaione (3). Phytochemical investigation of dichloromethane fraction resulted in the isolation of new epimeric isomers 1R/1S-1-methoxy-1-hydro-15-oxodehydrongaione (4) and (5). From the results, it was concluded that nonpolar fractions of B. daphnoides could exhibit anti-inflammatory and antiviral activities, probably owing to the major oxygenated sesquiterpenes.