In vitro biological activity and essential oil composition of four indigenous South African Helichrysum species

Abstract

Helichrysum species are used widely to treat various medical conditions. In this study, the anti-microbial, anti-oxidant (DPPH assay) and anti-inflammatory activity (5-lipoxygenase assay) of Helichrysum dasyanthum, Helichrysum felinum, Helichrysum excisum and Helichrysum petiolare were investigated. The essential oil compositions of these species were determined. The acetone and methanol extracts as well as the essential oils exhibited activity against Gram-positive bacteria, while both the methanol and acetone extracts of all four species were active in the anti-oxidant assay. The essential oils, on the other hand, displayed activity in the 5-lipoxygenase assay, which was used as an indication of anti-inflammatory activity. Two extracts exhibited promising activity in the anti-microbial assay, the acetone extract of Helichrysum dasyanthum with a MIC value of 15.63 μg/ml and the methanol extract of Helichrysum excisum with a MIC value of 62.5 μg/ml. The acetone extract of Helichrysum dasyanthum was the most active free radical scavenger in the DPPH assay (IC 50 of 9.53 μg/ml) while values for the anti-inflammatory activity of the essential oils ranged between 25 and 32 μg/ml. The essential oil compositions of three species ( Helichrysum dasyanthum, Helichrysum excisum and Helichrysum petiolare) were dominated by the presence of monoterpenes such as α-pinene, 1,8-cineole and p-cymene. In the oil of Helichrysum felinum, monoterpenes were largely absent. Its profile consisted of a variety of sesquiterpenes in low concentrations with β-caryophyllene dominating.