Antidiabetic, Antimicrobial, and Molecular Profiling of Selected Medicinal Plants

Natural products have been the center of attraction ever since they were discovered. Among them, plant-based natural products were popular as analgesics, anti-inflammatory, antidiabetic, and cosmetics and possess widespread biotechnological applications. The use of plant products as cosmetics and therapeutics is deep-rooted in Nepalese society. Although there are few ethnobotanical studies conducted, extensive research of these valuable medicinal plants has not been a priority due to the limitation of technology and infrastructure. Here, we selected 4 traditionally used medicinal plants to examine their bioactive properties and their enzyme inhibition potential. α-Glucosidase and α-amylase inhibitory activities were investigated using an in vitro model followed up by antioxidant and antimicrobial activities. The present study shows that ethyl acetate fraction of Melastoma melabathrium (IC(50) 9.1 ± 0.3 µg/mL) and water fraction Acacia catechu (IC(50) 9.0 ± 0.6 µg/mL) exhibit strong α-glucosidase inhibition. Likewise, the highest α-amylase inhibition was shown by crude extracts of Ficus religiosa (IC(50) 29.2 ± 1.2 µg/mL) and ethyl acetate fractions of Shorea robusta (IC(50) 69.3 ± 1.1 µg/mL), and the highest radical scavenging activity was shown by F. religiosa with an IC(50) 67.4 ± 0.6 µg/mL. Furthermore, to identify the metabolites within the fractions, we employed high-resolution mass spectrometry (LC-HRMS) and annotated 17 known metabolites which justify our assumption on activity. Of 4 medicinal plants examined, ethyl acetate fraction of S. robusta, ethyl acetate fraction of M. melabathrium, and water or ethyl acetate fraction of A. catechu extracts illustrated the best activities. With our study, we set up a foundation that provides authentic evidence to the community for use of these traditional plants. The annotated metabolites in this study support earlier experimental evidence towards the inhibition of enzymes. Further study is necessary to explore the clinical efficacy of these secondary molecules, which might be alternatives for the treatment of diabetes and pathogens.