Role of NMR Techniques in Identification and Evaluation of Antioxidant Phenolic and Flavonoid Phytochemicals: A Comprehensive Review

Abstract

Phenolic compounds and flavonoids are important natural antioxidants widely present in plants. Accurate identification, structural elucidation, and evaluation of these compounds are essential to understand their biological activity. Nuclear Magnetic Resonance (NMR) spectroscopy provides detailed structural and quantitative information in a non-destructive manner. This review highlights the application of one-dimensional (1D) and two-dimensional (2D) NMR, quantitative NMR (qNMR), and NMR-based metabolomics for the identification and evaluation of antioxidant phenolic and flavonoid compounds. Integration with in vitro antioxidant assays such as DPPH, ABTS, and FRAP is discussed. The correlation between structural features derived from NMR and antioxidant mechanisms, including free radical scavenging, metal chelation, and lipid peroxidation inhibition, is highlighted. Limitations, challenges, and future perspectives of NMR-based antioxidant research are also reviewed. This article aims to provide a comprehensive resource for researchers in pharmaceutical sciences and photochemistry. phytochemistry