Antibacterial activity of extracts of Three Croton Species Collected in Mpumalanga region in South Africa

Abstract: 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 (0.06mg/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

Screening of Twenty-four South African Combretum and six Terminalia Species (Combretaceae) for Antioxidant Activities

The dried leaves of Combretum and Terminalia species (Combretaceae)were extracted with acetone; hexane; dichloromethane and methanol. Thin layer chromatography (TLC) plates were developed under saturated conditions and sprayed with 0.22;2-diphenyl-1-picryl hydrazyl (DPPH) in methanol for antioxidant screening. Visualization of separated bands exhibiting antioxidant activities enabled the localization and the subsequent identification of the potential active compounds. The acetone and methanol extracts displayed the presence of antioxidant activity after spraying the chromatogram with DPPH. Hexane and dichloromethane extracts did not have any antioxidant activity. C. hereroense had the highest number of active compounds; followed by C. collinum ssp. taborense; which were 16 and 10; respectively. Acetone extracts of all tested Combretum species had 53 active bands and methanol had 55. All Terminalia species extracted with acetone and methanol had antioxidant activity. T. gazensis and T. mollis methanol extracts had 11 and 14 active compounds respectively in one of the solvent systems used. The qualitative DPPH assay on TLC was successfully used in this study to systematically assess the total antioxidant activity of the Combretum and Terminalia species extracts