High‐performance thin‐layer chromatography coupled attenuated total reflectance‐Fourier‐transform infrared and NMR spectroscopy‐based identification of <i>α</i>‐amylase inhibitor from the aerial part of <i>Asparagus racemosus</i> Willd

Abstract

Abstract Introduction α ‐Amylase inhibitors from natural sources are of interest for new drug development for the treatment of diabetes mellitus (DM). High‐performance thin‐layer chromatography (HPTLC) coupled bioassay guided isolation of bioactive compounds has been improved within last few years. Objective A microchemical derivatised HPTLC‐coupled attenuated total reflectance‐Fourier‐transform infrared (ATR‐FTIR) and nuclear magnetic resonance (NMR) spectroscopy was employed for profiling α ‐amylase inhibitor from the aerial part of Asparagus racemosus Willd. Methodology Asparagus racemosus Willd. aerial part extracted with different solvents ( n‐ hexane, chloroform, ethyl acetate, and methanol) and assayed to detect free radical scavengers and α ‐amylase inhibitor by 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) assay and starch‐iodine assay method, respectively. HPTLC‐coupled ATR‐FTIR and NMR spectroscopy was used to identify the α ‐amylase inhibitor. Results Methanolic extract of A. racemosus showed highest antioxidant activity (21.99 μg GAE/μL) where n‐ hexane extract showed lowest antioxidant activity (5.87 μg GAE/μL). The α ‐amylase inhibition was recorded as highest and lowest in ethyl acetate extract (13.13 AE/μL) and n‐ hexane extract (3.92 AE/μL), respectively. The deep blue zone of α ‐amylase sprayed TLC plate of extracts with hR F = 72 analysed for ATR‐FTIR and NMR spectroscopy which revealed the presence of stigmasterol is responsible for α ‐amylase inhibition. Conclusion The present work establishes the α ‐amylase inhibiting properties of A. racemosus maintaining its use for the treatment of DM as a traditional medicine. Bioassay guided isolation through HPTLC‐coupled ATR‐FTIR and NMR spectroscopy offers an effective method for the exploration of bioactive compounds such as α ‐amylase inhibitor from complex plant extracts.