The antibacterial activities of three
Croton
species were compared using bioautography and the serial microdilution methods. The methanolic extracts of all the species had low activity against
Escherichia coli
. The highest activity was observed with
Croton megalobotrys
against
Enterococcus faecalis with a minimal inhibitory concentration (MIC) value of 0.02 mg/ml.
Croton steenkapianus
extracts were the least active of the species investigated, only managing an MIC value of 0.625 mg/ml against
Pseudomonas aeruginosa.
Croton megalobotrys leaf powder was serially extracted using solvents of various polarities. The lowest MIC value (0.06 mg/ml) of the serially extracted fractions was observed with acetone against
Pseudomonas aeruginosa. The liquid-liquid fractions of the methanol extract of
Croton megalobotrys were also tested. The lowest MIC value of 0.02 mg/ml was observed with
n-hexane fraction against
Enterococcus faecalis. The carbon tetrachloride fraction was further fractionated using column chromatography with silica as the immobile phase. The resulting seven fractions were tested for activity following the bioassay-guided practice, and it emerged that the first three fractions had active compounds against Staphylococcus aureus when the bioautography method was used.
