15E-14

Arabinoxylan, which is a complex polysacchride in cereal cell wall, has been focused as a biological response modifier recently. Although it has valuable biololgical activities such as immunostimulant, anti-HIV, anti-cancer activities, etc., its bioavailability may be very low due to the insoluble complex with the other cell wall materials.

This research was performed to release and activate arabinoxylan from rice bran by using a combined process of extrusion and commercial hemicellulase treatment and to investigate its physicochemical and immunomodulating properties.

Arabinoxylan was characterized in terms of neutral sugar constituents by high performance anion exchange chromatography (HPAEC) and molecular weight by gel permeation chromatography (GPC). IFN-¥ãproduction and NK cell activation effects of arabinoxylan were examined by sandwich ELISA method and MTT assay, respectively.

The yield of arabinoxylan was approximately 5% from defatted and destarched rice bran. Rice arabinoxylan possessed an arabinose/xylose (Ara/Xyl) ratio of 0.59 and its number average molecular weight was approximately 6,000. IFN-¥ãproduction was increased dose dependently at a range of arabinoxylan concentration from 10 to 40 mg/ml in vitro. Addition of LPS to arabinoxylan significantly enhanced IFN-¥ãproduction compared to the control, untreated sample in vivo. Arabinoxylan also increased in vivo NK cell cytotoxicity for Yac-1 mouse tumor cells at effector:target (E:T) ratios of 25:1 and 50:1.

The results showed that extrusion and subsequent enzyme treatment was an industrially applicable tool for effective release of arabinoxylan with high yield and purity. It is anticipated that rice arabinoxylan can be used as an immunostimulating material in nutraceuticals and cereal based functional food.