Abstract:
Acacia nilotica (subalata) is small to big tree (2.5 – 15m) in the family Fabaceae. The species has a relatively wide ecological distribution in Asia and Africa. In Africa it is majorly distributed in southern and eastern regions.In Kenya, it grows in Coast, Eastern, Rift valley, Nyanza and Western regions. The prolonged use of Acacia nilotica extracts to make coffee like concoction by the locals whereas no scientific work has been done to compare the caffeine levels, phytoconstituents and evolutionary relatedness with Coffea arabica varieties. Therefore the aim of this work was to investigate phytoconstituents, caffeine levels, anti-bacterial activity and evolutionary analysis of Acacia nilotica (subalata) in comparison with Coffea arabica varieties. Methanol, ethanol and water extracts of stem bark of Acacia nilotica and Coffea arabica varieties were used to screen for phytochemicals while methanol and ethanol extracts were screened for anti-bacterial activity. Gentamycin and dimethyl sulfoxide were used as positive and negative controls respectively. Methanol and ethanol extracts were used for HPLC profiles on caffeine content. Using disc diffusion technique, organic extracts were screened against Pseudomonas aeruginosa and results showed that methanol extract had the highest activity. The minimum inhibitory concentrations (MICs) value was in a range between 5 and 12.5 mg/ml. The HPLC profiles displayed peak areas with same retention time; Acacia nilotica (7.452), Batian 27 (7.476) and Ruiru 11 (7.474) extract against retention time for standard caffeine (7.476) hence the samples have caffeine content. Ruiru 11 had the highest caffeine content (161.75 ± 39.16) followed by Batian 27(127.39 ± 14.83) and Acacia nilotica (subalata) (68.91 ± 17.39). They are statistically significant (p<0.05). Phylogenetic trees showing the evolutionary relationship between A. nilotica and Coffea arabicagenerated from MEGA using ribulose-1, 5-Bisphosphate Carboxylase (rbcL) gene sequences from Genbank revealed that A. nilotica and C. arabica are monophyletic.
