Antioxidant Activities of Compounds Isolated from Fermented Broth of Zygosaccharomyces Rouxii

Abstract

Previously, a sugar-tolerant strain of Zygosaccharomyces rouxii that had moderate antioxidant activity was isolated. In this investigation four active substances were isolated and their antioxidant activity was determined with different methods. The yeast strain (MAFF 237555) was cultured in yeast extract-malt extract (YM) medium, and the fermented broth was extracted with ethyl acetate. Dried solid extract was separated into neutral and acidic fractions. The neutral fraction was fractionated on a silica-gel column and purified on a Sephadex LH-20 column. The acidic fraction was recrystallized from acetone. The mother liquor was fractionated on two successive silica gel columns, followed by purification on a Sephadex column. The combined active aliquots were further purified on ODS and Phenyl high performance liquid chromatography (HPLC) columns, successively. The chemical structures of isolated substances were analyzed by electron ionization mass spectrometry (EIMS) and nuclear magnetic resonance (NMR) spectroscopy and were identified as tyrosol, succinic acid, vanillic acid and para-hydroxy benzoic acid. Using available commercial compounds, we determined the antioxidant activity of isolated substances with seven assay methods was determined and compared to natural and synthetic standard compounds. It was observed that the activity of each substance varied with the assay mode. No single substance could be identified as an all-round highly active antioxidant, which was also true with the standard compounds. The diverse activities suggested that Z. rouxii could be used as a source of wide-spectrum natural antioxidant.