Ethanolic Extract of Nigella sativa Seeds Lacks the Chemopreventive Efficacy in the Post Initiation Phase of DMH-Induced Colon Cancer in a Rat Model

Nigella sativa, belonging to the Ranunculacea family, is a versatile phytochemical mine bestowed with multi-dimensional medicinal effects. The current study was performed to investigate the chemopreventive efficacy, if any, of the ethanolic extract of indigenous Nigella sativa seeds (ENS) and to evaluate its potentials on tumor progression during the initiation and post initiation phases of Dimethylhydrazine-induced colon carcinogenesis in a rat model. ENS treatment during the initiation phase unveiled chemopreventive effect manifested by significant reductions in tumor incidence, multiplicity and tumor volumes. Histopathological findings and modified Duke’s classification of tumors provided evidence that ENS, administered in the initiation phase, is capable of delaying progression, restricting invasion and attenuating aggressiveness of colon tumors. These results imply that ENS may be a promising candidate in the primary prevention of colon cancer. On the contrary, we demonstrated that ENS lacked chemopreventive and tumorigenesis inhibitory effects in the post initiation phase. We speculate that the chemopreventive effect of ENS might be due to the synergistic actions of various constituents present in the extract. However, extensive studies are warranted and more efforts need to be dedicated to fractionate, analyze and to further appraise the anticancer effect of ENS before any definitive conclusions can be drawn.