An efficient way from naringenin to carthamidine and isocarthamidine by Aspergillus niger

Biotransformation of naringenin with Aspergillus niger CGMCC 3.4628 yielded two hydroxylation products which were identified unambiguously as 6-hydroxylnaringenin (carthamidin) and 8-hydroxylnaringenin (isocarthamidin) by ESI–MS and 1H-NMR. Both products simultaneously arrived at high level after 48 h in the biotransformation process. The highest conversion efficiency of carthamidin was 0.38 mg/mg of naringenin and that of isocarthamidin was 0.43 mg/mg of naringenin. Antioxidant property assay using a thin layer chromatography-bioautographic-based DPPH scavenging method demonstrated that both hydroxylation metabolites exhibited much stronger activity than naringenin. The high efficiency and convenient procedure makes the biotransformation with A. niger described in current work a potential way to produce carthamidin and isocarthamidin.