Antibacterial Potency of Acyclic diester, Oleic acid and β-amyrin tetradecanoate from Acacia lahai and Leucas calostachys against antibiotic resistance bacteria

Nicholas Kimutai, PhD.^1*Philip A. Ogutu¹Rahab Kamau¹Charles Mutai²

• ¹School of Natural Science, Masinde Muliro University of Science and Technology, Kakamega, Kenya
• ²Department of Medical Laboratory Sciences, School of Public Health Biomedical Sciences and Technology, Masinde Muliro University of Science and Technology, Kakamega, Kenya

The escalation in antibiotic resistant microorganisms has led to the search for new, more effective antimicrobial agents. Natural products from plants may therefore, serve as an alternative source of substances for treatment of these infections. Traditional practitioners use the concoctions of Acacia lahai and Leucas calostachys extracts for the treatment of wounds, skin diseases, coughs, ulcers, and intestinal ailments. This is because they are rich in powerful antibacterial compounds. The objective of this study was to isolate bioactive compounds from A. lahai and L. calostachys through bioassay-guided fractionation. Methods: Bioactivity testing was determined against selected microbes using disc diffusion and broth micro dilution method as recommended by Clinical Laboratory Standard Institute (CLSI). Pure compounds were isolated through chromatographic procedures and their structures elucidated based on 1D and 2D NMR analyses. Results: Fractionation yielded two fatty acids namely; 5-(2, 5-dimethylhexyl) 1isopentyl 3-hydroxy-2-methylpentanedioate (acyclic diester) (1) and Cis oleic acid (2) from A. lahai and L. calostachys, respectively. In addition, L. calostachys yielded a terpenoid, β-amyrin tetradecanoate (3). The three compounds were selectively active against the tested microorganisms, with MIC of 25.0 mg/ml and 100.0 mg/ml shown by Cis oleic acid and βamyrin tetradecanoate against Staphylococcus aureus, respectively. The two compounds were isolated and tested for antibacterial activities from this plant for the first time. In addition, Acyclic diester named as 5-(2, 5-dimethylhexyl) 1-isopentyl 3-hydroxy-2-methylpentanedioate (2) was also isolated and screen for antibacterial activities for the first time from extracts of Acacia lahai. Conclusion: A. lahai and L. calostachys extracts and compounds promoted antibacterial activities against multi-drug resistant bacteria. This provided valuable insights into the development of effective antimicrobial agents.