Effect of Hibiscus sabdariffa extract and Nigella sativa oil on the growth and aflatoxin B1 production of Aspergillus flavus and Aspergillus parasiticus strains

This study was undertaken to evaluate the inhibitory effect of Hibiscus sabdariffa calyx extract at concentrations of 5, 7.5, 10 and 12.5 g/100 ml and Nigella sativa oil at concentrations of 1, 2 and 3 ml/100 ml on the growth and aflatoxin B1 production by Aspergillus parasiticus (CBS 921.7) and Aspergillus flavus (SQU 21) strains. The inhibition of aflatoxin B1 production by the different concentrations of H. sabdariffa calyx ranged between 91.5-97.9% and 87.1-93.3% for A. flavus and A. parasiticus strains, respectively, whereas the inhibition by different concentrations of N. sativa oil ranged between 47.9 and 58.3% for A. flavus and 32-48% for A. parasiticus strains. The different concentrations of H. sabdariffa calyx and N. sativa oil had no significant effect on the growth of either Aspergillus species. Neither H. sabdariffa calyx nor N. sativa oil detoxified pure aqueous aflatoxin. Our results suggest that H. sabdariffa calyx and N. sativa oil extracted from seeds had metabolic effects on aflatoxin biosynthesis pathway of both Aspergillus species and can be used as an effective biocontrol and non-toxic biopreservatives in food industry against aflatoxin contamination.

► We examined the effect of different concentrations of Hibiscus sabdariffa calyx and Nigella sativa oil extracts on the fungal growth and aflatoxin B1 production of Aspergillus flavus and A. parasiticus strains. ► The two extracts had no significant effect on the mycelial growth of either Aspergillus species and do not detoxify pure aqueous aflatoxin. ► The extracts of H. sabdariffa calyx and Nigella sativa oil had metabolic effects on aflatoxin biosynthesis pathway. ► Both extracts can be used as an effective biocontrol and non-toxic biopreservatives in food industry and of no harzerdous effect on human health.