FT-IR characteristics, phenolic profiles and inhibitory potential against digestive enzymes of 25 herbal infusions

The present study aimed to analyse the FT-IR vibrational characteristics and concentration of phenolic compounds in 25 herbal plants using Fourier transform infrared (FT-IR) spectroscopy and Ultra-High Performance Liquid Chromatography (UHPLC) techniques, respectively, and to evaluate its in vitro potential to inhibit enzymes related type 2 diabetes and obesity. The vibrational spectra regions-3400-3200 cm⁻¹-indicated hydroxyl group (O-H) and H-bonded stretching, which is characteristic of polyphenolic compounds. A wide range in phenolic compounds was found among the samples. Caffeic acid is the predominant phenolic compounds in the samples. Total phenolic content ranged from 5.02 mg GAE/g DW to 102.39 mg GAE/g DW. A moderate correlation (R²) between antioxidant activity and α-amylase inhibition was 0.46, (p < 0.05) while that (R²) of p-coumaric acid and α-glucosidase inhibition was 0.54, (p < 0.05). Moreover, the herbal infusions showed potential to inhibit digestive enzymes, the highest being on the infusion based on a cup-serving basis.