Extraction, Purification of Taro Globulin and Its Inhibitory Activity on α-Amylase and α-Glucosidase

Objective: Exploring taro globulin regulating activity in vitro. Methods: Taro globulin was extracted by phosphate buffer. The effects of solid-liquid ratio, temperature, time and times on protein extraction were investigated with protein extraction rate as an index. Based on the test, response surface methodology was used to optimize the extraction process. The crude protein was purified by DEAE-52 ion cellulose column chromatography. The purity of purified globulin was detected by high performance liquid chromatography, and its isoelectric point and molecular weight were determined. The inhibitory activity and inhibition kinetics of taro globulin on α -amylase and α-glucosidase were studied, and acarbose was used as positive control to evaluate globulin activity of regulating blood glucose in vitro. Results: The optimum extraction conditions were as follows: The solid-to-liquid ratio was 1:16 g/mL, the temperature was 41 ℃, and the time was 124 min. Under these condition, the extraction rate was 36.75%±0.31%, the yield was 0.70%±0.04%, and the purity of the protein was 85.72%±0.47%. The purified globulin was detected by high performance liquid chromatography with a main peak with purity of 93.27%, yield of 0.20%±0.01%, isoelectric point of 5.6 and molecular weight of about 22 kDa. The taro globulin exhibited inhibition on the two enzymes with dose-effect relationship. The IC₅₀ was (0.75±0.10) mg/mL for α-amylase and was (2.09±0.19) mg/mL for α-glucosidase The IC₅₀ of acarbose were (0.61±0.13) mg/mL and (0.69±0.16) mg/mL. The results showed that the inhibitory activity of taro globulin on α-amylase was slightly lower than acarbose, while the inhibitory activity on α-glucosidase was much lower than acarbose. The inhibition type was reversible and uncompetitive inhibitor, with K_i=(0.61±0.05) mg/ml for α-amylase and K_i=(0.26±0.02) mmol/L/L for α-glucosidase. Conclusion: The extraction process of taro globulin was optimized, and taro globulin was purified. It was found that taro globulin has certain activity of regulating blood sugar in vitro, which would have certain guiding significance for the research and development of functional food and the increasing of added value of taro products.