EVALUATION OF ALPHA-GLUCOSIDASE INHIBITORY ACTIVITY AND QUALITY DETERMINATION OF MADHUCA LONGIFOLIA (J. KOENIG EX L.) MACBR. AND MORUS ALBA L. PLANT MATERIALS

Abstract

The alpha-glucosidase inhibitory activity and the quality determination of Madhuca longifolia (J.Koenig ex L.) Macbr. and Morus alba L. plant materials were evaluated. Boiling water extract of leaves from both plants exhibited potent inhibitory effect on alpha-glucosidase with the IC50 values of 15.23±1.32 and 195.73±34.84 µg/mL for M. longifolia (L1) and M. alba cultivar Buriram 60 from Nakorn Ratchasima, respectively, compared with acarbose at 763.92±22.27 µg/mL. All samples were determined for loss on drying, heavy metal contamination, total phenolic content, microbial contamination, and the fingerprints of Fourier Transform Infrared (FT-IR) spectra, Gas Chromatography-Mass Spectroscopy (GC-MS) chromatograms and Liquid Chromatography-Diode Array Detector (LC-DAD) chromatograms. All tested samples complied with Thai Herbal Pharmacopoeia (THP) 2019, The Association of Southeast Asian Nations (ASEAN), The World Health Organization (WHO), The International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use (ICH), The United States Pharmacopeia (USP) 40 and Thai Pharmacopoeia (TP) 2005 guidelines, in loss on drying, heavy metal and microbial contamination. However, leaf samples of M. longifolia and M. alba cultivar Buriram 60 from Buriram province were contaminated with non-pathogenic Clostridium species. GC-MS chromatograms of M. longifolia leaf extract showed high amount of phytol, linolenyl alcohol, neophytadiene and palmitic acid, while that of M. alba showed high amount of phytol and fatty acids such as palmitic acid, oleic acid and stearic acid. The High-Performance Liquid Chromatographic (HPLC) method was developed to quantify gallic acid and quercetin in M. longifolia, and chlorogenic acid, caffeic acid, rutin and quercetin in M. alba leaf extracts. The FT-IR and chromatographic fingerprints could be used for the identification and authentication of M. longifolia leaf and flower, and M alba leaf. The developed HPLC method will be useful for the quantification of active constituents and quality assessment of M. longifolia and M. alba leaf in the future. Moreover, leaf of M. longifolia and M. alba will be potential sources for hypoglycemic compounds.

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