Partial hydrolysis enhances the inhibitory effects of konjac glucomannan from Amorphophallus konjac C. Koch on DNA damage induced by fecal water in Caco-2 cells

This study determined effects of diets containing 5% (w/w) unhydrolysed konjac glucomannan (KGM), and its acid-hydrolysate, fractions 1 and 2 (F1, F2), with degrees of polymerisation 8 and 4, respectively, on the cytotoxicity and DNA damage of fecal water-treated Caco-2 cells. Oligofructose was used as a positive control. In addition, the possible mechanisms for these effects were investigated. Results indicated that KGM, F1, F2 and oligofructose diets similarly increased the survival rate of fecal water-treated Caco-2 cells compared with the FF diet. F2 exerted the greatest protective effects, amongst KGM-based fibres, on fecal water-induced DNA damage. The prebiotic effects of F1 and F2, were also better than that of KGM. However, the fecal water from the group fed KGM, rather than partially-hydrolysed KGMs, exerted the greatest ferrous ion-chelating ability. In conclusion, partially-hydrolysed KGMs exerted greater protective effects than did the unhydrolysed KGM on fecal water-induced DNA damage, mainly by their prebiotic effects.