Browsing by Author "Njau, Efrem-Fred"

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Antimicrobial Activity of Tetradenia riparia (Hochst.) Lamiaceae, a Medicinal Plant from Tanzania
(European Journal of Medicinal Plants, 2014-08-08) Njau, Efrem-Fred; Alcorn, Jane-Mary; Buza, Joram; Chirino-Trejo, Manuel; Ndakidemi, Patrick
Aims: To evaluate the antibacterial activity of Tetradenia riparia crude extracts against Escherichia coli, Staphylococcus aureus and Enterococcuss faecalis. The phytochemicals that are responsible for the bioactivity were also screened. Study Design: In vitro assay of antibacterial properties. Place and Duration of Study: Samples were collected from Njari village at Uru North in Moshi district located in north eastern Tanzania. Extraction and phytochemical analyses were conducted at the College of Pharmacy and Nutrition, University of Saskatchewan, Saskatoon, Canada. Antimicrobial assay was carried out at Department of Microbiology, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Canada between March 2013 and August 2013. Methodology: Agar well diffusion test was used to determine antimicrobial activity of the plant extracts. Ethanol, methanol, hexane and distilled water were used as extracting solvents. These extracting solvents were removed by vacuo evaporator. The resulting concentrated gummy-like materials were dissolved in Dimethysulfoxide (10% DMSO). Chemical tests were used to determine the group of phytochemicals present in the sample extracts. Results: Sensitivity testing results indicated that S. aureus was found to be more sensitive than E. coli and E. faecalis. Tetradenia riparia methanolic extracts from the root were the most active with zone of inhibition values of 29.33±0.88mm, 21.33±0.33mm and 20.0±1.0mm in diameter against S. aureus, E. faecalis and E. coli respectively. The relative inhibitory zone diameter (RIZD) was calculated. The highest percentage values of relative inhibition zone diameter of 84±5.06% (S. aureus) and 76±6.86% (E. coli) were demonstrated by T. riparia root methanolic extracts. However, T. riparia leaf and root extracts using hexane as well as leaf extracts using water did not show any antibacterial activity against E. faecalis. Root methanolic and ethanolic extracts demonstrated the minimum inhibitory concentrations ranging from 1.25mg/ml to 5.00mg/ml. Phytochemical screening of crude extracts from leaf and root of T. riparia revealed the presence of alkaloids, flavonoids, phenolics, saponins, tannins and sterols. Conclusion: The study findings suggest likelihood of designing and developing potentially active antibacterial drug from T. riparia. Further studies should concentrate on the investigations of not only leaf but also the root part of the plant.
Antimicrobial and Antioxidant Activity of Crude Extracts of Rauvolfia caffra var. caffra (Apocynaceae) From Tanzania
(Canadian Center of Science and Education, 2014-09-24) Njau, Efrem-Fred; Alcorn, Jane; Ndakidemi, Patrick; Chirino-Trejo, Manuel; Buza, Joram
As part of an effort to search for extracts and compounds with new antimicrobial efficacy to fight against bacterial resistance, the antibacterial activity of Rauvolfia caffra var. caffra (Sond.), a plant of family Apocynaceae used in Traditional Medicine in Tanzania, was investigated. Ethanol, methanol and water extracts from leaf, stem and root barks were tested against three species of bacteria namely Escherichia coli (ATCC 25922) (Gram -ve), Staphylococcus aureus (ATCC 25923) (Gram +ve) and Enterococcus faecalis (ATCC 51299) (Gram +ve) using Agar-well diffusion assay method and minimum inhibitory concentration on Mueller-Hinton Agar plates. The extracting solvents were removed by vacuo evaporator to obtain gummy-like extracts. This was then dissolved in dimethylsulfoxide (10% DMSO). The DMSO without plant extracts was used as a negative control whereas Gentamicin® as the standard antibiotic was used as a positive control. The Zone of Inhibition (ZOI) measured in mm and Relative Inhibitory Zone Diameter (RIZD) was calculated. Results showed that R. caffra exhibited antimicrobial inhibitory activity at a range of 1.25 to 5.0 mg/ml with activity most prominent with methanol extract (ZOI of 28.33± 0.33 mm and RIZD of 95% for S. aureus; and ZOI of 26.66 ± 0.33 mm for E.coli and 19.0 ± 0.57 mm for E. faecalis at P< 0.05). To characterize further, the alkaloid from the root bark was extracted according to the standard procedure. The antioxidant activity of the alkaloids and ethanolic extracts was determined using 2, 2-diphenyl-1-picrylhydrazyl (DPPH) and reducing capacity assays. The results indicated that alkaloid fraction of the root and 80% ethanolic extracts of stem bark exhibited high antioxidant activity. The phytochemical analysis indicated that R. caffra is rich in alkaloids, anthraquinones, anthocyanoides, flavonoids, saponins, tannis and reducing sugars. This study provides supportive evidence that methanol and ethanol extracts of R. caffra can be used as herbal medicine in control of E.coli, S. aureus and E. faecalis.