Nigella sativa extract kills pre-malignant and malignant oral squamous cell carcinoma cells

Abstract

In this study, the potential of Nigella sativa was evaluated in the management of oral cancer through assays designed to mimic conditions expected when chewing the whole seeds or use of a seed extract. For this purpose, a water-based extract of N. sativa seeds was prepared, mimicking the chewing process. This extract demonstrated significant cytotoxic effect on oral cancer and pre-cancerous leukoplakia cells in vitro at a much lower concentration than the predicted oral concentration that could be achieved upon seed chewing. When the active constituent(s) in this water-based N. sativa seed extract, was explored significant quantities of the compound α-hederin was detected but only modest quantities of thymoquinone suggesting that thymoquinone is not fully released into the aqueous medium during the chewing process. While the N. sativa seed extract induced a different effect on the cells than that of pure thymoquinone, α-hederin alone induced a very similar effect on the cells to that of the extract. These results suggest that α-hederin and not thymoquinone, is the major component of the seed that is responsible for the inhibitory effect observed in vitro. Therefore, chewing N. sativa whole seeds or applying a concentrated extract on the oral lesions may be an inexpensive, widely available, and effective option for patients at risk of developing oral cancer who are receiving no other preventive treatment.