Optimisation of an extraction conditions for Rumex nepalensis anthraquinones and its correlation with pancreatic lipase inhibitory activity

Abstract

Rumex nepalensis Spreng. (Polygonaceae) is an edible plant rich in anthraquinones, that significantly inhibits Pancreatic Lipase (PL), a key enzyme in the dietary fat digestion. The effectiveness of Ultrasonic Assisted Extraction (UAE) of R.nepalensis was investigated using ethyl acetate as a solvent. Further, optimization of extraction conditions required for maximizing the PL inhibitory activity was determined using response surface methodology with Box-Behnken Design (BBD with three factor, 17 experimental runs). Extraction time (A, min), solid: solvent ratio (B, g/mL) and temperature (C, °C) were selected as the variables. The optimum conditions were established as extraction time (37 min), solid: solvent ratio (1:10.5) and extraction temperature 33 °C. However, till date, no HPTLC reports are available for the simultaneous quantification of chrysophanol and physcion from R. nepalensis. Thus, chrysophanol and physcion were quantified in various extractives of R. nepalensis via. a validated HPTLC method and a positive correlation were obtained with PL inhibition activity (Pearson’s r = 0.801 and 0.755 for chrysophanol and physcion respectively), that justified the PL inhibition potential of R. nepalensis derived anthraquinones.