Difference of Acidic Adding Effect in Ethanol Extraction of White Mulberry Stem Bark (Morus alba) and DPP-4 Inhibiting Activity Screening for Identifying its Antidiabetic Potential

Objective: Murberry (Morus alba) is one of the plants that can be used to treat diabetes and bioactive compounds that play a role are apigenin. Apigenin compounds have been reported to have an antidiabetic effect and are found in the form of glycosides. To separate apigenin from its glycosides, it takes the process of hydrolysis using acid. This study aims to look at the differences between ethanol extracts without hydrolysis with acids and ethanol extracts which are hydrolyzed by acid and determine their activity as dipeptidyl peptidase-4 (DPP-4) inhibitors in vitro. Methods: Morus alba stem bark dry powder was extracted MAE using 96% ethanol with acid hydrolysis using HCl 2 N and extracted without acid hydrolysis then apigenin levels can be measured by each extraction process using HPLC. DPP-4 activity was evaluated using glycyl-prolyl-7-amino-4-methyl coumarin (Gly-Pro-AMC) substrate then the inhibitory effect of extracts was determined based on the number of free AMCs by measuring fluorescence at excitation wavelengths of 350-360 nm and emission wavelengths of 450-465 nm using micro-plate readers. Sitagliptin is used as a positive control of DPP-4 inhibition in this test. Results: The ethanol extraction method with acid hydrolysis can attract more apigenin compounds than the ethanol extraction method without acid hydrolysis. The level of apigenin in the sample of ethanol extract with acid hydrolysis was 0.16%, and in the ethanol extract without acid hydrolysis was 0.04%. The amount of inhibitory activity of DPP-4 Morus alba stem bark extract was 23%, which is 0.33 times the inhibition of sitagliptin activity. Conclusion: Extraction methods with acid hydrolysis are more effective in attracting apigenin compounds than without acid hydrolysis. Morus alba stem bark extract has an anti-diabetic effect through the mechanism of action of DPP-4 inhibitors can be used as a reference for therapy of diabetes mellitus from natural ingredients.