He a Professor of Chemistry at the University of Nairobi, Kenya. He has an extensive experience in teaching of Organic Chemistry and conducting research in the field of Natural Products Chemistry. For the last thirty years, he has been involved in the investigation of Eastern African plants for bioactive natural products. This has resulted in the publication of 90 articles in peer reviewed journals (h-index of 32, Citations 2692 in Google Scholar, as of July 03, 2020). He has also co-authored three books on medicinal plants of East Africa; served as reviewer to several international journals and examined some 30 PhD and MSc theses in Africa. In 2015, He is serving as a subject editor of the journal Phytochemistry Letters, which is the official organ of the Phytochemical society of Europe. He is an Editorial Board member of the Journal of Natural Products and Journal of Ethnopharmacology as of January 2018. In terms of mentorship, he has-supervised sixteen PhD and thirty-five MSc students. He has served as the Program Officer (2006-2009), and later as the Assistant Secretary (2009-2013) of a regional organization called, the Natural Product Research Network for Eastern and Central Africa (NAPRECA). As one of the leaders of this network, he has been involved in organizing a number of symposia and workshops, and also coordinated postgraduate scholarships, which has promoted collaborative research in the region. In recognition of this he was elected as a Fellow of the African Academy of Science as of February 2017.