Phytochemical variability of selected medicinal plants from different agro-climatic zones in Kenya

Medicinal properties of plants are a factor of their phytochemical content and profile. Agro-climatic factors such as temperature, sunlight, water availability, and soil composition can influence the profile of bioactive phytochemicals in plants and hence their medicinal potential. The study investigated the phytochemical variability in leaf extracts of selected medicinal plants, mango, guava, and avocado, from different agro-climatic zones in Kenya. Fresh healthy leaves were sampled from two hundred and twenty-seven mango (83), guava (85), and avocado (59) accessions in nine different geographical areas. Methanol extracts of the leaves were prepared and assayed for total phenol content (TPC), total flavonoid content (TFC), and antioxidant activity. The TPC and TFC distribution in the extracts did not correlate with the agro-climate zones. However, patterns were observed attributable to geographical and specific agro-climatic parameters. Further, correlation analyses showed that specific agro-climatic parameters significantly affected TPC and TFC. Specifically, guava TPC, avocado TPC, and mango TFC had a moderately negative correlation with rainfall and soil moisture. Mango TFC had a moderate correlation with altitude and temperature. However, none of the correlations was high (r ≥ 0.5), suggesting the effect of other confounding factors. No discernible trend was observed with the antioxidant properties. Though some geographical patterns and correlations with agro-climatic parameters were established in the study, TPC, TFC, and antioxidant activity and agro-climatic zones may not be conclusively used to characterize these medicinal plants. Future studies may narrow on specific bioactive molecules and specific agro-climatic parameters.