Entrapment of sugars and vitamins by polysaccharide gel from durian fruit-hulls in vitro

Abstract

The polysaccharide gel (PG) extracted from fruit-hulls of durian (Durio zibethinus L.), an agricultural waste material from plant, was a value-added polysaccharide gel product. PG is a water-soluble polysaccharide fiber composed of galacturonic acid, glucose, arabinose, rhamnose and fructose. Effects of PG on entrapment of sugars (glucose and sucrose) including fat-soluble vitamin (vitamin A) and water-soluble vitamin (vitamin B1) were studied in vitro by dialysis technique using semi-permeable membrane dialysis bag and everted jejunal sac of rat. Moreover, glucose trapping property of PG was compared to that of glucomannan (GM), a commercial product of soluble polysaccharide fiber. Glucose 0-2% w/v in 0-3% PG was dialysed 0-4 hours in Ringer buffer, pH 7. Glucose inside and outside the dialyzing bag was analyzed by colorimetric method using glucose oxidase enzyme reaction. Increasing concentration, i.e. 2 and 3% PG resulted in increasing glucose trapped inside dialysis bag and decreasing glucose released from dialysis bag after 1, 2, 3 or 4 hours of dialysis. PG showed significant lower capability for glucose entrapment than that of GM at 1, 2 and 3% of the soluble polysaccharide fiber after 2 hours of dialysis. In vitro studies using everted jejunal sac of rat showed similar result of decreasing of glucose transport in the presence of increasing concentration of 2 and 3% PG after 1 hour of dialysis. Study on effect of PG on sucrose entrapment by dialysis technique using semi-permeable membrane dialysis bag and analysis of sucrose by HPLC technique showed that increasing PG concentrations resulted in decreasing sucrose released to outside of dialysis bag. Vitamin A, all-trans retinyl acetate, was mixed with ascorbic acid, bile salt and 0-3% PG in Ringer buffer pH 7, and dialysis in container covered with aluminum foil under nitrogen gas in dark room for 2 hours, increasing of trapped vitamin A was observed in the presence of increasing concentration of 1-3% PG. Vitamin B1, thiamin hydrochloride, was mixed with 0-3% PG in Ringer buffer pH 7, after 2 hours of dialysis, increasing of trapped vitamin B1 was obtained in dialysis bag and decreasing of vitamin B1 released in the presence of increasing concentrations of 23 % PG. This study suggested that sugars (glucose and sucrose), fat-soluble vitamin (vitamin A) or water-soluble vitamin (vitamin B1) can be entrapped by 2% PG. The present investigation showed that it is possible to perform the in vitro dialysis study using semi-permeable membrane dialysis bag as a simple method for preliminary study of nutrients retention property of soluble polysaccharide before performing the high cost in vivo study on polysaccharide effects with nutrients absorption.