Evaluation of Inhibitory Activity of α-Amylase and α-Glucosidase Enzymes and Aantioxidant Capacity of Metabolites Obtained from of Lactobacillus delbrueckii ssp bulgaricus PTCC1900 Culture Media

Today, the use of Lactobacill strains and their metabolites is the new strategies in control of diabetes and oxidative stress. Therefore, the present study aimed to investigate the antidiabetic and antioxidant properties of metabolites obtained from of Lactobacillus delbrueckii ssp. bulgaricus culture media. The samples were evaluated including cell free supernatant (CFS), cell free extracts (CFE), cell free supernatant of fermented milk (CFS-FM) and bioactive peptides separated from ultrafiltration (3,5,10 kDa). The ability of bacteria in proteolysis of protein of  fermented milk (FM) was evaluated by O-phthaldialdehyde method compared with non-fermented milk (NFM). The antidiabetic activity was measured based on inhibition of α-amylase and α-glucosidase. The antioxidant activity was evaluated by inhibition of 2,2-Diphenyl-1-picrylhydrazyl (DPPH) and 2,2-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS). The results showed that the sample of CFS-FM inhibited α-amylase (25%) and α-glucosidase (26.6%) enzymes. Among the peptide fractions, fraction  of >10 kDa with higher protein content (13.816 mg (had the highest inhibition of α-amylase (80.64%) and α-glucosidase enzyme (54%) (p<0.05). The inhibitory efficiency ratio (IER) showed that the 3-5 kDa fraction had more inhibitory than other peptide fractions (p<0.05). Also, the CFS and CFE inhibited α-glucosidase enzyme by 50% and 25%, respectively. In case of antioxidant properties, it was observed that the free radicals scavenging of CFS-FM increased compared with NFM (p<0.05). Also, the peptide fractions of 3-5 kDa (80.85%) and >10 kDa (43.63%) had the highest DPPH and ABTS free radicals scavenging. The antioxidant capacity of trolox equivalent from peptide fractions (µmTE/mg protein) showed that the <3 kDa fraction had the highest antioxidant activity (p<0.05). The ability to free radicals scavenging in CFS and CFE was observed. Results indicate the importance of  Lactobacillus delbrueckii as a starter culture and its functional role.