Antibacterial activity of south African Helichrysum species

Acetone extracts of Helichrysum callicomum, H. glomeratum, H. hypoleucum, H . odoratissimum, H. piloselium and H. rugulosum were investigated for antib acterial activities against ten bacteria using the agar diffusion method. E picuticular (shaken) ana homogenized extracts of H. hypoleucum, H odoratiss imum and H. rugulosum significantly inhibited the growth of Bacillus cereus , B. pumilus, B. subtilis, Micrococcus kristinae and Staphylococcus aureus (all Gram-positive bacteria) and Enterobacter cloacae (Gram-negative) at a concentration range of 0.01 to 1.0 mg/ml. In addition, the epicuticular ext ract of H. hypoleucum was active against Escherichia coli and Pseudomonas a eruginosa whereas the homogenized extract only had activity against P. aeru ginosa. None of the other six extracts inhibited the growth of E. coli, Kle bsiella pneumoniae, P. aeruginosa and Serratia marcescens, all Gram-negativ e bacteria. The extracts of H. glomeratum and H. pilosellum had no activity against any of the organisms tested. Shaken extracts proved to be more bio active than homogenized extracts.