Identification and Comparison of Functional Groups in Medicinal plants using Attenuated Total Reflectance–Fourier Transform Infrared (ATR-FTIR) Spectroscopy. ATR-FTIR of Medicinal Plants
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Abstract
The biochemical profiles of a few chosen medicinal plant leaves in both fresh and shade-dried forms were examined and compared using attenuated total reflectance–Fourier transform infrared (ATR-FTIR) spectroscopy. Major functional groups were to be identified, spectral variations across treatment conditions were assessed, and the impact of drying on spectral clarity was to be ascertained. Samples were scanned in the mid-infrared range (4000–400 cm⁻¹), and spectra were generated using baseline correction, normalization, and averaging among repeats. Prominent bands of absorption that correspond to O–H stretching (~3300 cm⁻¹), C–H stretching of aliphatic groups (2920–2850 cm⁻¹), C=O and C=C vibrations of phenolic and flavonoid compounds (~1700–1600 cm⁻¹), and carbohydrate-related C–O–C and C–O stretching (1100–1000 cm⁻¹) have been consistently identified across species. Fresh samples displayed wide and powerful O–H bands due to greater moisture content, which concealed underlying biomolecular characteristics. Shade-drying considerably decreased water-associated absorptions, increasing the resolution of protein (amide I and amide II), lipid, and polysaccharide bands. Interspecific differences in band intensities were found through comparative analysis, suggesting variations in the composition of phytochemicals like phenolics, alkaloids, terpenoids, and glycosides. The study shows that ATR-FTIR is a quick, non-destructive analytical method that can produce repeatable biochemical fingerprints for therapeutic plants. Furthermore, shade-dried leaves were shown to provide sharper spectral fingerprints than fresh material, indicating their applicability for spectroscopic authentication and phytochemical screening. These findings provide baseline FTIR spectrum assignments for the investigated species and show the potential of vibrational spectroscopy for quality control
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