Opuntia ficus-indica mucilage reduces wheat starch in vitro digestibility br

Nopal (Opuntia ficus-indica) is traditionally used in Mexico for the treatment of diabetes mellitus. Several clinical studies have reported an anti-hyperglycemic effect from the plant, but the underlying mechanisms are still controversial. In this study, the potential beneficial effects of using nopal juice for controlling glucose release during the hydrolysis of starch molecules, and the possible mechanisms of action involved, were explored using in vitro testing. To this end, wheat starch dispersions (3 g/100 g water) were gelatinized, subjected to either hydrochloric acidic (pH 2.0) or alpha-amylase (pH 6.9) hydrolysis, and glucose production was monitored. Nopal mucilage (NM) extracted from nopal cladodes was added to starch dispersions which were completely gelatinized. NM reduced the acidic hydrolysis of starch by about 50%, although NM also contributed to glucose production. Some insights pointed out to a mechanism involving the formation of electrostatic complexes between starch and nopal polysaccharides, which are resistant to acidic hydrolysis. On the other hand, nopal hydrolysis also reduced the amylolytic starch hydrolysis by 40%, possibly due to the formation of enzyme-polyphenol complexes which hindered the action of the enzymes upon the starch molecules, plus the fact that the alpha-amylase was unable to hydrolyze the nopal mucilage. Thus, the formation of different types of complexes produced mechanical hurdles that hindered starch hydrolysis and glucose production.