Optimization of ultrasound-assisted extraction conditions for total phenols with anti-hyperglycemic activity from Psidium guajava leaves

The high concentration of total phenolic compounds (TPC) in Psidium guajava leaf extracts (GvEx) is correlated to its anti-hyperglycemic activity. In this study, we established the optimum ultrasound extraction conditions for maximizing TPC yield. The response surface methodology (RSM) was employed for empirical model building. The maximum value of TPC (26.12%) was obtained at solvent to solid ratio (v/w) of 12.1, extraction temperature of 59.8 degrees C, and extraction time of 5.1 min. The anti-hyperglycemic activity of GvEx was compared to the commonly used diabetic drug acarbose. The IC50 of GvEx for alpha-amylase and alpha-glucosidase inhibition was 50.5 mu g/mL and 34.6 mu g/mL, respectively. However, the IC50 of acarbose for alpha-amylase and alpha-glucosidase inhibition was 95.3 mu g/mL and 1075.2 mu g/mL, respectively. In conclusion, GvEx obtained under optimum extraction conditions had higher anti-hyperglycemic activity than acarbose. In addition, the recommended extraction procedures for GvEx save time and are environmentally friendly. (C) 2014 Elsevier Ltd. All rights reserved.