Hybrid drying of Murraya koenigii leaves: anti-diabetic and anti-ageing activities

This study aims to compare the anti-diabetic and anti-ageing effect of the Murraya koenigii leaves by using the drying method of convective hot-air drying (40, 50 and 60 degrees C) and two hybrid drying methods through microwave vacuum-drying (6, 9 and 12 W/g) and convective hot-air pre-drying followed by microwave vacuum finishing-drying (50 degrees C followed by 9 W/g), in addition to the freeze-drying, which was used as a control method. The anti-diabetic activity was evaluated by using alpha-amylase and alpha-glucosidase inhibition method, while the anti-ageing activity was measured by using acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibition effect. The results indicated that the dried leaves of M. koenigii were more selective towards alpha-glucosidase inhibition with the percentage ranging from 7.92 to 23.57% at the concentration of 62.52 +/- 22.18 to 20.39 +/- 2.01 mg dried leaves/mL. Concerning the anti-ageing activity, the inhibition effect of AChE was significantly weaker compared to BChE inhibition, revealing that the dried M. koenigii leaves were more selective towards BChE inhibition with the percentage ranged from 79.47 to 87.07%. Furthermore, the Page model and diffusion models showed a good fitting of the model to the empirical data of drying kinetics with the highest coefficient of determination (0.9996; 0.9995) and the lowest values of root-mean-square error (0.0102; 0.0090) and Chi-square coefficients (0.0010; 0.0008). Overall, microwave vacuum-drying is the recommended drying method to be used for M. koenigii leaves due to its promising result obtained for the inhibition of alpha-glucosidase and BChE.