Chemometric Profiling of Clinacanthus nutans Leaves Possessing Antioxidant Activities using Ultraviolet-visible Spectrophotometry

The goal of this study was to identify active metabolites responsible for the antioxidant activities of Clinacanthus nutans leaf extracts using an ultraviolet-visible (UV-Vis) spectrophotometric-based metabolomics approach. The extracts were subjected to three antioxidant assays including diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay, nitric oxide (NO) radical scavenging activity, and metal chelating assay. Spectrophotometric data were analysed using soft independent modeling of class analogy (SIMCA) software. Principal component analysis (PCA), partial least squares (PLS), and orthogonal PLS discriminant analysis (OPLS-DA) were used to conduct multivariate data analysis. The ethanolic extract of C. nutans leaves had the highest antioxidant capacity. Rutin, betulin, lupeol, orientin, schaftoside, vitexin, and chlorogenic acid were detected at wavelengths of 318 to 359 nm and identified as potential antioxidants in ethanol and water extracts. OPLS-DA provided clearer discrimination of extracts into four distinct clusters with improved spatial distribution as compared with PCA model. CV-ANOVA of OPLS-DA and PLS supported the reliability of models when p < 0.000. Creditability of PLS model was further proved when R2 and Q2 were nicely intercepted in PLS permutation plot. This study highlighted the potential of using UV-Vis spectrophotometry in metabolomics approaches to assess the metabolite variation in samples, thereby contributing to comprehensive knowledge of plants with antioxidant activities, aiding with the development of nutraceuticals for treating antioxidant damages and related disorders.