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

Introduction: alpha-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 alpha-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 alpha-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 alpha-amylase inhibitor. Results: Methanolic extract of A. racemosus showed highest antioxidant activity (21.99 mu g GAE/mu L) where n-hexane extract showed lowest antioxidant activity (5.87 mu g GAE/mu L). The alpha-amylase inhibition was recorded as highest and lowest in ethyl acetate extract (13.13 AE/mu L) and n-hexane extract (3.92 AE/mu L), respectively. The deep blue zone of alpha-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 alpha-amylase inhibition. Conclusion: The present work establishes the alpha-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 alpha-amylase inhibitor from complex plant extracts.

Automated summary

This study successfully identified alpha-amylase inhibitor from the aerial part of Asparagus racemosus Willd. using microchemical derivatised HPTLC coupled with ATR-FTIR and NMR spectroscopy, highlighting its potential anti-diabetic properties.