Production of nigragillin and dihydrophaseic acid by biotransformation of litchi pericarp with Aspergillus awamori and their antioxidant activities

Biotransformation with Aspergillus awamori could degrade the bound bioactive compounds of plant tissues into free form and induce the biosynthesis of novel chemicals. In this work, two bioactive compounds with high levels were produced from litchi pericarp via A. awamori fermentation. They were purified and identified to be nigragillin and dihydrophaseic acid by nuclear magnetic resonance spectroscopy and mass spectrometry. The anticancer activity, DNA protection effect and antioxidant activity of these two compounds were evaluated. Dihydrophaseic acid had significantly inhibitory effect against HepG2 and HeLa cells with IC50 values of 41.92 ± 6.15 and 79.37 ± 9.78 μg/mL, respectively. Nigragillin showed a better DPPH radical scavenging activity than dihydrophaseic acid. Dihydrophaseic acid possessed good lipid peroxidation inhibition effect, hydroxyl radical scavenging activity, and DNA protection effect even at a low dosage. The results indicated that biotransformation with A. awamori was a good way to produce bioactive compounds.