Magister Scientiae (Medical Bioscience) - MSc(MBS) / There is increasing concern worldwide by researchers with regards to the assessing of safety and therapeutic consumption of the plants used in traditional medicine. Date palm pollen (DPP) and flax seed have been used traditionally to improve fertility in Libya. DPP extracts have shown several reproductive beneficial effects. In vivo, studies have revealed the ability of DPP to increase sperm concentrations, ameliorate the testicular toxicity induced by cadmium and lead, raise testosterone, as well as LH and FSH hormone levels. Flax seed phytochemical analysis showed lots of valuable components such as lignans and α linolenic acid to which were attributed its positive health effects like antitumor, antioxidant and protective effects against coronary heart diseases. Moreover, flax lignans have both estrogenic and antiestrogenic potential. This study was aimed at testing the effects of Libyan DPP and flax seed on the Sertoli (TM4) cell line and human breast adenocarcinoma (MCF - 7) cell line. Different concentrations (0.01, 0.1, 1, 10, 100 and 1000 μg/ml) of ethanolic extracts of DPP and flax seed, respectively, were used to assess the morphology of TM4 and MCF - 7 cells after 24 and 72 hours exposure. Mitochondrial dehydrogenase activity as a marker of cell viability was measured by MTT assay after 24 and 72 hours exposure. Apoptotic effects were assessed by flow cytometeric APO percentage assay. TM4 cell production of Inhibin - B hormone and GGT enzyme activity under the effects of DPP or flax seed was determined by use of ELISA kits. Transepithelial electrical resistance (TEER) assay were used to detect the effect of DPP or flax seed on TM4 cell monolayer integrity. Finally the plants potential phytoestrogenic activity was determined by use of E - SCREEN assay in MCF – 7 breast cancer cells. Higher concentrations of DPP significantly increased the activity of mitochondrial dehydrogenase enzyme of TM4 cells after 24 hours associated with increasing cell number as detected in a microphotograph. Flax seed concentrations less than 100 μg/ml reduced TM4 cell viability but there were no morphological changes visible after 24 hours. MCF - 7 cells viability was reduced after 24 and 72 hours treatment with DPP and flax seed. DPP concentrations beyond 1 μg/ml significantly raised the TEER of TM4 monolayer over 72 hours while flax seed treatments caused a significant increase only after 72 hours of exposure. TM4 cells GGT activity increased significantly after exposure to higher concentrations of DPP and all flax seed concentrations. Significant stimulatory effects of all the concentrations of DPP or flax seed on TM4 inhibin - B hormone productions have been detected. Apoptotic studies showed no significant changes. E - SCREEN assay resulted in significant reduction in MCF - 7 proliferation rate under the effect of low concentrations of DPP or flax seed. Higher concentrations of the plant extracts, however, stated to increase MCF – 7 cell proliferation, this exerts weak estrogenic activities. In conclusion, the main finding of this study is that DPP and flax seed showed stimulatory effects on TM4 cells proliferation. The resistivity of TM4 cells monolayer which reflect the integrity of blood – testis barrier (BTB) was also significantly increased as well as inhibin - B production and GGT enzyme activity. In addition DPP and flax seed respectively showed inhibitory effects on MCF - 7 cells viability. This study indicated that DPP or flax seed may enhance spermatogenesis through their stimulatory action on Sertoli cells. Moreover, both plants could reduce breast cancer cells viability. However, further investigations are required to elucidate the exact mechanisms behind these obtained findings.