Optimization and fractionation of quercitrin-rich extract from Melastoma malabthricum leaves and its bioactivities

Abstract

Melastoma malabathricum (M. malabathricum) is also known as “senduduk”. It is a small shrub belonging to the family Melastomaceae. According to scientific studies, the leaves of this plant have been proven to possess many beneficial bioactivities and its extract has great therapeutic potential. However, limited research has been carried out, especially on the processing technologies for the bioactive extract of M. malabathricum leaves. Therefore, this study focused on the effect of temperatures on the drying kinetics and quality of M. malabathricum leaves in determining the optimum drying temperature. Degradation of quercitrin above 50oC suggesting that this could be the optimum temperature ranges. Midilli et al model shows to have the best fit to the experimental data of drying among the selected thin layer models with the high correlation coefficient (R2>0.98). Response surface methodology was employed to optimize the ultrasonic assisted extraction and solid phase fractionation processes of M. malabathricum leaves using central composite design. The optimized extraction process conditions were solid to solvent ratio (1 mg: 20.83 ml), ultrasonic amplitude (68.6%) and particle size (440 μm) to obtain 13.4 % yield. The optimized fractionation conditions were loading concentration of crude extract (9.13 mg/ml), ratio of eluent system (70.4 %, methanol) and volume of eluent system (18.24 ml). The result showed that the content of quercitrin was increased from 10.31 mg/g in crude extract to 36.02 mg/g after fractionation using solid phase extraction (SPE). An equilibrium dependent extraction (EDE) model has successfully applied in describing the extraction process. EDE model is more accurate with R2 value more than 0.90 and root mean square error less than 0.001. This explains the mass transfer resistance caused by quercitrin diffusion is negligible. The anti-diabetic activity of samples was successfully determined using dipeptidyl peptidase IV assay in vitro and in silico. The IC50 of extract and fraction were found to be 48.25μg/ml and 30.71μg/ml, respectively. The lower IC50 of fraction revealed the higher anti-diabetic activity of the fraction than crude extract. The binding energy of quercitrin was -6.21 kcal/mol which means the lowest of binding energy has high potential on anti-diabetic activity. The processing technology of quercitrin rich extract from M. malabathricum has been established based on the ultrasonic assisted extraction and followed by SPE clean-up process.