Anti-microbial Activity of Tamarind (Tamarindus indica L.) Extracts from Semi-arid Eastern Parts of Kenya

Natural products are alternatively used in the control of pests and diseases because they are highly available, cheap and environmentally friendly. Tamarind (Tamarindus indica) belongs to the Leguminosae family and subfamily Fabaceae. Its native to Africa, Asia and S, America. Tamarind tree produces pod like edible fruits that are widely used in cuisines globally. The fruits have been reported to be therapeutic in several pharmacopoeias. The seeds have been explored in the treatment of diabetes, fevers, intestinal infections and diarrhea. In Kenya, tamarind is present in the arid and semi-arid areas and there is limited information on its antimicrobial activity. This study aimed at evaluating the antimicrobial activity of leaf and fruit extracts from tamarind trees growing in semi-arid Eastern Kenya. Fruits and leaves of tamarind were sequentially extracted using methanol and water and evaporated using a rotary evaporator at 40°C. The extracts were then reconstituted using the solvent and stored at 4°C. The pathogenic bacteria were cultured on 28 g/l of nutrient agar and the extract-impregnated discs were inoculated on the plates and cultured at 37 °C for 24 hrs. Sub-culturing was done to obtain pure isolates of the pathogens. The extracts were tested for their activity against Bacillus subtilis, Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli. Data on bacterial inhibition zones were recorded after 24 hrs. The results revealed that there was no significant difference in inhibition between the leaf and fruit extracts. However, there was a significant inhibition difference between the five study regions and in extraction solvents against B. subtilis and P. aeruginosa. Tamarind extracts were not effective against S. aureus and E. coli. When compared to common antibiotics Ampicillin, Methanol leaf extracts from accessions KT007, E017 and E020 had a higher inhibition than B. subtilis; also, water fruit extracts from accessions E008 and E014 had a higher inhibition than B. subtilis. Methanol leaf extracts from accessions KT012, E001, KB008 and KB011 had higher inhibition against P. aeruginosa compared to Streptomycin, Kanamycin, and Co-trimoxazole. Water fruit extracts from the accession of KT012 had a higher inhibition of P. aeruginosa compared to Streptomycin, Kanamycin, and Co-trimoxazole. Water leaf extracts from accessions of KT001, KB004, KB005, KB011, KB012, KB014 and KB016 had a higher inhibition of P. aeruginosa compared to kanamycin, gentamycin, streptomycin, ampicillin, and co-trimoxazole. Tamarind extracts did not inhibit S. aureus and E. coli. In conclusion, Eastern Kenyan tamarind had limited potential against B. subtilis and P. aeruginosa.