Integrated Evaluation of NADES for Green Extraction of Bioactive Compounds from Strawberries: A Study on Anthocyanin, Antioxidant Activity, Chemometric FTIR Profiling

Abstract

Strawberries (Fragaria x ananassa) are a rich source of anthocyanins and phenolic compounds with strong antioxidant properties. This study introduces an integrated approach combining quantitative analysis, including total anthocyanin content, total phenolic content, and antioxidant activity via DPPH assay, along with qualitative profiling using Fourier Transform Infrared (FTIR) spectroscopy and Principal Component Analysis (PCA). The aim was to thoroughly assess the extraction efficiency of 5 Natural Deep Eutectic Solvents (NADES), synthesized from choline chloride and various organic acids (citric, oxalic, malic, tartaric and lactic), in comparison to ethanol. Among these, NADES E (choline chloride:lactic acid) showed the highest extraction performance, yielding 125.57 ± 12.22 mg/100 g anthocyanins, 11,032.02 ± 785.13 mg GAE/g phenolics, and 89.15 ± 6.1% antioxidant activity. Interestingly, NADES A (choline chloride:citric acid) produced similar bioactive yields but exhibited the most intense FTIR absorbance in regions associated with phenolic functional groups (-OH, C=O and C=C), indicating a different compound affinity or preservation capacity. This suggests that while NADES E is superior for quantitative yield, NADES A might better retain specific chemical fingerprints. Moreover, PCA demonstrated clear separation of NADES A, C, and E from ethanol, highlighting the superior compound selectivity and profile retention of NADES. These findings highlight the importance of integrating multiple analytical techniques to evaluate both the efficiency and selectivity of green solvent systems for extracting bioactive compounds from plant matrices.