Climate Change–Associated Modulation of Phytochemical Composition and Antimicrobial Potential in Medicinal Plants of the East African Region: A Review of Evidence

Medicinal plants remain important components of healthcare systems in East Africa, where indigenous knowledge has supported their use for generations. Their therapeutic value is largely associated with secondary metabolites whose biosynthesis and accumulation are influenced by environmental conditions. Climate change may therefore affect medicinal plants not only shifts in productivity but also through alterations in the quantity and composition of bioactive constituents. This review examines the relationship between climate variability, phytochemical composition, and antimicrobial potential of seven medicinal plants distributed in East Africa: Azadirachta indica, Tamarindus indica, Ocimum gratissimum, Aloe secundiflora, Warburgia ugandensis, Toddalia asiatica, and Tithonia diversifolia. Emphasis is placed on temperature and rainfall variability, drought stress, habitat alteration, secondary metabolism, and antimicrobial evaluation using minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). Evidence from the reviewed studies indicates that climatic stress can modify phytochemical concentration and composition rather than uniformly reducing them. Moderate stress may stimulate the production of defensive metabolites, whereas severe or prolonged stress can impair plant growth and secondary metabolism. Consequently, climate variability may contribute to species-specific, seasonal, spatial, and temporal differences in phytochemical profiles and antimicrobial activity. Reports of increased quantities, repeated administration, and longer treatment periods for herbal remedies exist, but direct evidence linking these practices to climate-induced phytochemical changes remains limited. The review emphasises the need for integrated long-term studies combining climate monitoring, phytochemical profiling, antimicrobial testing, ethnobotanical information, and conservation strategies to better understand how climate change may influence the medicinal quality and sustainability of East African plant resources.