New Antioxidative Activities of the Cereals Fermented with Aspergillus spp. And Their Usefulness as Functional Food Materials

2002 Fiscal Year Final Research Report Summary

• Project/Area Number: 13680165
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: 食生活
• Research Institution: Sugiyama Jogakuen University
• Principal Investigator: ESAKI Hideo Sugiyama Jogakuen University, School of Life Studies, Associate Professor, 生活科学部, 助教授 (90097642)
• Project Period (FY): 2001 – 2002
• Keywords: Rice bran / Buckwheat seed / Koji / A. oryzae / A. saitoi / Antioxidant / Diferulic acid / Ferulic acid

Research Abstract

Antioxidative components in the methanol extract prepared from the koji fermented with A. oryzae KBN 943 were fractionated by Amberlite XAD-2 column chromatography. Two potent antioxidants in the 80% methanol eluate were isolated by preparative HPLC using ODS columns and identified as 8-O-4'-diferulic acid (8-O-4'-diFA) and 5, 5'-diferulic acid (5, 5'-diFA). Ferulic acid (FA) in the 60% methanol eluate and these diFAs were produced from rice bran by alkaline hydrolysis. These ferulic acid analogs are considered to be present as cell wall components, which are liberated by the esterases produced from the Aspergillus sp..
8-O-4'-diFA exhibited stronger antioxidative activities than FA and α -tocopherol in both a liposome system and DPPH radical scavenging test. The antioxidative activities and the contents of diFAs and FA in rice bran koji increased during koji making periods. There was a good correlation between them.
The antioxidative screening test of buckwheat koji used 8 kinds of Aspergillus spp. was carried out. The koji fermented with A. saitoi exhibited significantly strongest antioxidative activity. Its activity increased remarkably during koji making periods. The antioxidative activities were especially enhanced at the stage of sporulation. BK-1 (Mw : 290) was isolated as a principal antioxidant by the various chromatographies. This antioxidant, which was contained in large amount in the buckwheat koji, exhibited strong DPPH radical scavenging ability in addition to the inhibitory effects on tyrosinase and hyaluronidase activities.
It was suggested that the ethanol extract from rice bran koji, buckwheat koji and corn-feed koji could be used as antioxidant materials. These powders in baked cookies also could protect from lipid peroxidation during the baking and the storing of them.