Jonas Mwatseteza

Evaluation of Malawian Vernonia glabra (Steetz)Vatke leaf and Securidaca longepedunculata (Fresen) root extracts for antimicrobial activities

Article history: Received on: 18/08/2012 Revised on: 29/08/2012 Accepted on: 05/09/2012 Available online: 28/11/2012 The aqueous, ethanol and acetone crude extracts and dichloromethane, hexane, ethyl acetate and nbutanol fractions of the Securidaca longepedunculata roots and Vernonia glabra leaves were studied for their antimicrobial activity against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Candida albicans using agar well diffusion method. The phytochemical presents, as well as the minimum inhibitory concentration (MIC) and minimum bacteriacidal/fungicidal concentration (MBC/MFC) of the extracts were also determined using standard methods. Results obtained indicated that Vernonia glabra leaves acetone extracts had excellent antimicrobial activity against E. coli, P. aeruginosa and ethanol extracts against S. aureus. The n-butanol fractions had the best activity against E. coli and S. aureus, dichloromethane fraction against P. aeruginosa and ethyl acetate fraction against C. albicans. For S. longepedunculate root ethanol extracts showed best activity against E. coli, acetone extract against P. aeruginosa and aqueous extract against C. albicans. The n-butanol fractions had best activity against E. coli, P. aeruginosa and C. albicans. These results verified the claims by traditional healers in Malawi that the plants extracts treats bacteria related ailments such as diarrhoea and could be a potential source for development of phytomedicine.

Evaluation of the bright greenish yellow fluorescence test as a screening technique for aflatoxin-contaminated maize in Malawi

The bright greenish yellow fluorescence (BGYF) test has been used with varying success in screening for aflatoxins in maize. This test was applied to 180 maize samples collected from different markets within 12 districts of Malawi in order to evaluate its performance against high performance liquid chromatographic analysis. The number of BGYF grains in 2.5 kg unground samples ranged from 0 to 35 and about 49% of all tested samples had aflatoxin concentrations ranging from 1 to 382 μg/kg. A total of 65 (36%) of the examined unground samples showed no BGYF. The European Commission recommends a false negative rate of less than 5% for a screening technique to be acceptable. In this study, four BGYF grains per 2.5 kg unground maize sample successfully indicated an aflatoxin contamination of >10 μg/kg (10 μg/kg being the maxium tolerable level proposed by the Common Market for Eastern and Southern Africa), with a 4.4% false negative rate. In this case, the amount of confirmatory analyses would be reduced by 63%...