Molecular Weight Affected Antioxidant, Hypoglycemic and Hypotensive Activities of Cold Water Extract from Pleurotus citrinopileatus

Cold water extract of P. citrinopileatus (CWEPC) was fractioned into 4 fractions, PC-I (<1 kDa), PC-II (1-3.5 kDa), PC-III (3.5-10 kDa), and PC-IV (>10 kDa), by ultrafiltration. The antioxidant activities, the inhibition of pancreatic alpha-amylase, intestinal alpha-glucosidase, and hypertension-linked angiotensin converting enzyme (ACE), as well as the contents of polysaccharides, protein, and phenolic compounds of 4 fractions were determined. The results showed that lower MW fractions exerted a higher antioxidant activity, which was correlated to phenolic contents. The high molecular fraction (PC-IV) exhibited significantly higher inhibitory activity on alpha-amylase, alpha-glucosidase, and ACE compared to CWEPC and the other 3 lower MW fractions (<10 kDa), which was more related to protein contents. The inhibition capability of CWEPC and PC-IV on alpha-amylase activity was 1/13.4 to 1/2.7 relative to that of acarbose, respectively. Kinetic data revealed that PC-IV fraction followed a noncompetitive inhibition pattern on alpha-glucosidase activity. The study demonstrated that various MW fractions and types of components contribute to different biological functions of P. citrinopileatus and it is protein constituents but not peptides responsible for the hypoglycemic potential of CWEPC.