Plants as sources of anti-gonococcal agents Moola M. Nyambe 1 , Edet Archibong 2 , Kazhila C. Chinsembu 3
1 Department of Physics, Chemistry and Material Science, Faculty of Agriculture, Engineering and Natural Sciences (FAENS), University of Namibia, Namibia, 2 Department of Pharmaceutical Sciences, School of Pharmacy, Namibia, 3 Department of Biochemistry, Microbiology and Biotechnology, Namibia In Namibia, plants are commonly used as traditional medicine for treating sexually transmitted infections (STIs) including gonorrhea. The rising gonorrhea infection rates and Neisseria gonorrhoeae ’s resistance to antibiotics, pose a potential health crisis. Therefore, it is vital to find an effective anti-gonococcal agent. Plants used in treating gonorrhea, are potential sources of novel compounds for developing such a drug. However, the safety and efficacy of these ethno-medicinal plants are not established. This study aims to evaluate the anti-gonococcal activity of extracts from plants used to treat gonorrhea in Namibia and to investigate the enzyme inhibition potential of isolated compounds based on their ability to bind to Neisseria gonorrhoeae carbonic anhydrase (NgCA)’s. The study uses bioassay guided fractionation, chromatographic and spectroscopic techniques to test the biological activity, isolate, and characterize the structures of the active compounds. In-silico studies, including density functional theory, molecular docking, and quantitative structure-activity relationship, are used to predict the activity and the interaction of active compounds with NgCA. So far one compound, xerantholide from Pechuel- loeschea leubnitziae has been isolated and shown to have anti-gonococcal activity with MIC 50 = 0.095 mg/mL. Ten of the 16 tested plant crude extracts exhibited anti-gonococcal activity with MIC range of 2.5 – 10 mg/mL. Molecular docking results show xerantholide interact with NgCA active site via hydrogen bonding, non-polar alkyl and pi-alkyl interactions with predicted binding affinity of -6.8 kcal/mol. Future studies will be directed towards identifying novel anti-gonococcal agents targeting enzyme activity disruption. References 1. Dillon J-AR, Parti RP, Thakur SD. Antibiotic resistance in Neisseria gonorrhoeae : Will infections be untreatable in the future? Culture. 2015;35(1). 2. Nyambe MM, Archibong EF, Sekhoacha M, Chinsembu KC. In-vitro anti-gonorrheal activity of a sesquiterpene lactone, xerantholide isolated from the leaves of Pechuel-loeschea leubnitziae . South African J Bot. 2022;147:314–8.
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