¹H NMR Chemical Profile and Antioxidant Activity of Eugenia punicifolia Extracts Over Seasons: A Metabolomic Pilot Study

Eugenia punicifolia (Kunth) DC. is a medicinal plant used to treat diseases related to oxidative processes. In this work, H-1 nuclear magnetic resonance (NMR) spectroscopy and multivariate analysis have been employed to track the chemical changes and antioxidant activity of dimethyl sulfoxide (DMSO) extracts from E. punicifolia leaves over seasons. Principal component analysis (PCA) applied to H-1 NMR allowed discriminating DMSO extracts from leaves collected in the dry and rainy seasons and pointed out sucrose, catechin, and epicatechin as responsible for separating dry season samples and quercetin, acid gallic, glucose, and fatty acids contributed for rainy samples grouping. Notably, antioxidant assays revealed that dry season extracts exhibited a higher radical scavenging capacity. When those compounds were submitted to partial least squares-discriminant analysis (PLS-DA) only sucrose and fatty acids presented variable importance projection (VIP) score > 1, both metabolites are related somehow to the defense mechanisms of the plant. This pilot study may suggest new experimental approaches for more effectively monitoring the spectrum-effect relationship of E. punicifolia leaf extracts.