Helichrysums: antibacterial and monoamine oxidase inhibitory activity of South African summer-rainfall species

A large number of Helichrysum spp. (Asteraceae) is used traditionally in southern Africa to treat a variety of ailments. It is a popular ingredient in wound dressings [1] and is an important plant culturally as it is burned at almost all traditional gatherings. Several species have been shown to have a sedative effect [2] and antibacterial activity both against Gram-positive and Gram-negative bacteria [3]. Antibacterial activity was detected using MIC values of crude extracts ranging from 6.25 to 0.049mg/mL. Of the 9 Helichrysum species assayed for activity against Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, and Bacillus subtilis, 2 species, H. ruderale and H. argyolepis showed broad spectrum activity. Besides H. hesbaceum and H. adenocarpum that did not display antibacterial activity, the rest were active either against one or two bacteria. MAO-B inhibitors are known to increase the basal dopamine levels in the nigrostriatal dopaminergic input pathway, a fact that is utilised in the symptomatic therapy for Parkinson's disease [4].Seven species were assayed for MAO-B inhibitory activity using a peroxidase-linked photometric assay. H. agyrolepis (IC₅₀=0.1µg/mL), H. umbraculigerum (IC₅₀=4.3µg/mL) and H. ruderale (IC₅₀=3.3µg/mL) were the most active species, although all species tested exhibited some MAO-B inhibition activity.

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