MSc (Microbiology) / Department of Microbiology / Background: The medicinal value of plants lies in some chemical substances that produce a definite physiological action in the human body. The secondary metabolites help the plants to survive hash conditions and could be used by humans as supplements of their health, as foods additives or for medicinal purposes. This bioactive compounds are not always beneficial to human beings, and some of this plants bioactive compounds can be toxic or genotoxic to human cells. This study used several methods to evaluate of phytochemical constituents and mutagenic properties of Coccinia rehmanni and Jatropha zeyheri plant extracts. Methodology: Methanol was used for extraction of the bioactive compounds from the two selected plants, filtered with Whatman filter paper and evaporated with rotary evaporator. The extracts were fractionated using open column chromatography. Chemical and TLC methods were used to determine phytochemicals of the study plants extracts and fractions. The plants extracts and fractions were tested against Vero cell lines in order to evaluate cytotoxicity and genotoxicity of the plants. NucRed and LTR Hoechst 33342 dyes were used for cytotoxicity and genotoxicity respectively. For the evaluation of cytotoxicity and genotoxicity Quantification of live and dead cells for the screening assay was performed using the ImageXpress Micro XLS Widefield Microscope and acquired images analyses using the MetaXpress software and Multi-Wavelength Cell Scoring Application Module. Antimutagenicity of plants extracts was observed using PARP universal colorimetric assay kit. Acquired data was transferred to an EXCEL spreadsheet and data was analyzed. Results and discussion: C. rehmanni (12.03%) yielded more extract than J. Zeyheri (8.20%). the two plants had different compound composition and were in different stages of maturity. The study revealed the domination of Terpenoids, Cardiac glycosides, Phenolic and tannis. With an exception of two fraction fractions all the fractions was found to be toxic to an extent were genotoxicity of such fraction could not be concluded. The reason for such extreme toxicity could be due to the influence of the retained alcohol during rotary evaporation. xvi | P a g e Conclusion: this study provides and add to existing knowledge on the phytochemicals mutagenicity and anti-mutagenicity of C. rehmanni and J. Zeyheri medicinal plants. The study serves as scientific proof that extensive use of this plant in traditional medicine for treatment of various ailments may lead to some irreversible damages. / NRF