In vitro antimicrobial activity of some Libyan medicinal plant extracts

In vitro antimicrobial activity of 32 extracts (ethanol, hexane, chloroform, and methanol) from eight different Libyan medicinal plants, namely Artemisia herba-alba Asso (Compositae), Globularia alypum L. (Globulariaceae), Helichrysum stoechas, DC. (Compositae), Peganum harmala L. (Zygophyllaceae), Polygonum equisetiforme Sibth. & Sm. (Polygonaceae), Pulicaria crispa (Forssk.) Oliv. (Compositae), Rosmarinus officinalis L. (Labiatae), and Thymus capitatus Hoffmanns & Link. (Labiatae), was determined against seven bacteria and one yeast strain using the broth microdilution method. The results show that all plants tested possessed antimicrobial activity against at least one of the examined strains at a concentration <= 8 mg/ml. The extracts from H. stoechas, P. equisetiforme, P. crispa, R. officinalis, and T. capitatus exhibited strongest activity against Gram-positive bacteria with minimum inhibitory concentrations (MICs) ranging from 0.5 to 8mg/ml. Only a few extracts showed inhibitory activity against Gram-negative strains in this test, whereas those of the H. stoechas and P. harmala were among the strongest ones (MICs range 4-8mg/ml). High anticandidal activity was observed for P. harmala, P. crispa, and T. capitatus, with MICs ranging from 0.25 to 1 mg/ml.