Phytochemistry and therapeutical potential of new Nigella Sativa genotypes from Australia

The phytochemistry and anticancer properties of nine Nigella sativa genotypes grown in central Queensland, Australia, were determined and compared. The genotype AVTKS6 recorded the highest seed yield (2195 kg ha−1) and was associated with the highest plant density (112 plants m−2), whereas AVTKS8 had the highest harvest index (0.42). The seed yield was positively corrected with the plant density at harvest and capsules/plant at harvest, but not with the harvest index. All nine genotypes of N. sativa tested showed antioxidant potential (532–805 mg TXE 100 g−1) and total phenolic content (TPC) and ranged from 794 mg GAE 100 g−1–1126 mg GAE 100 g−1. The thymoquinone (TQ) content of nigella seeds varied between the genotypes, ranging from 0.896 (AVTKS4)–1.728% w/w (AVTKS8). Seed yield was not correlated with TQ and TPC concentration, however, a negative correction between the seed yield and TAC was evident. Water extracts of the genotypes showed higher cytotoxic activity against the cell lines tested more prominently against HeLa cells (44–57% cell viability) compared to the MeOH extracts. Cytotoxic activity of MeOH extracts against HeLa cells were not different from the negative control and no activity was evident against the HT29 and PH5CH8 cell lines. However, PH5CH8 cells exposed to water extracts of AVTKS1, 3, 4, 5, 6, 7, and 8 showed only about 39–50% cell viability after 48 h of treatment, indicating that while the water extracts had beneficial cytotoxic activity against HeLa and HT29 cancer cell lines, it may also have toxic effects against healthy human cells. Principal component analysis of chemical and bioassays of the genotypes suggested that the AVTKS5 genotype was closely linked with desirable traits, highlighting it as an ideal cultivar.