Chemical composition and biological activity of the essential oil obtained from Bupleurum marginatum (Apiaceae)

Bupleurum marginatum is a herb indigenous to the southern and southwestern part of China. It is widely used in many Chinese prescriptions. We aimed to investigate the chemical composition, antioxidant, anti-inflammatory, antimicrobial and in-vitro cytotoxic activity of the hydrodistilled and extracted essential oil from B. marginatum to validate some of its ethnopharmacologial uses.

The essential oil of the aerial parts of B. marginatum was analysed by capillary gas chromatography (GLC/FID) and gas chromatography-mass spectrometry (GLC/MS). The ability of the oil to reduce diphenylpicrylhydrazine (DPPH(.)) and to prevent the degradation of deoxyribose were used to evaluate the antioxidant activity. Inhibition of both prostaglandin E(2) production and lipoxygenase were used to assess the anti-inflammatory activity. Antimicrobial activity was studied in vitro against a range of bacteria and fungi. The in-vitro cytotoxicity of the essential oil on six human cancer cell lines (HepG2, Caco-2, CCRF-CEM, HeLa, MiaPaCa-2 and MCF-7) was examined using the MTT assay.

Seventy-two components, comprising almost 94.29% of the total peak area, were identified in the analysis. The main components were tridecane (13.18%), undecane (10.42%), pentadecane (8.71%), beta-caryophyllene (5.53%) and beta-caryophyllene oxide (5.29%). The ability of the oil to reduce diphenylpicrylhydrazine (DPPH(.)) and to prevent the degradation of deoxyribose were used to evaluate the antioxidant activity and the corresponding IC50 values (drug concentration which resulted in a 50% reduction in inhibition of the activity) were found to be 3.66 mg/ml and 17.4 microg/ml, respectively. Inhibition of both prostaglandin E(2) production and lipoxygenase were used to assess the anti-inflammatory activity (IC50 of 63.64 microg/ml for lipoxygenase, 26.04% inhibition of prostaglandin E(2) at 25 microg/ml dose). The oil also showed a significant in-vitro antimicrobial activity against Gram positive pathogens (Streptococcus pyogenes and Streptococcus agalactiae) with minimum inhibitory concentration (MIC) values ranging from 0.125 up to 4.00 mg/ml. The in-vitro cytotoxicity of the essential oil on six human cancer cell lines (HepG2, Caco-2, CCRF-CEM, HeLa, MiaPaCa-2 and MCF-7) examined using the MTT assay revealed the highest activity to be in the CCRF-CEM cell line with an IC50 (concentration which resulted in a 50% reduction in cell viability) of 46.01 microg/ml after 24 h treatment.

The essential oil of B. marginatum exhibited a promising anti-inflammatory activity along with strong cytotoxicity against many cancer cells (CCRF-CEM and HepG2) mediated through induction of apoptosis, and this in-vitro activity make its local traditional uses rational. However, its limited antimicrobial activity indicates that a combination with other drugs is essential for effective use. Further selectivity testing is required to evaluate the effect of the oil against normal cells.