ESTABLISHMENT OF A PROTOCOL FOR TESTING ANTIMICROBIAL ACTIVITY IN SOUTHERN AFRICAN MACROALGAE

Six southern African seaweeds, two Chlorophyta, Phaeophyta and Rhodoph yta, were used to test for antibacterial activity against Bacillus sub tilis, Staphylococcus aureus, Acinetobacter Iwoffi and Escherichia col i. Extracts were prepared using a range of organic solvents (acetone, chloroform, diethyl ether, 80% ethanol and methanol), by soaking groun d seaweed samples in the extraction solvent, evaporating to dryness, a nd redissolving in the respective solvent. In addition, milled and gro und samples were boiled in 80% ethanol for 4 h. Crude extracts were te sted for antibacterial activity using three application techniques, vi z paper discs, direct spotting and wells, and onto three types of agar plates, viz seeded agar, bacterial lawns and overlay agar. Inhibition zone diameters were measured and analysed by multifactorial analysis of variance. Boiling milled seaweeds in 80% ethanol, with application of the extracts into 6.1 mm wells in overlay agar constituted the test protocol which yielded the highest activity indices.