LC−MS/MS−based metabolite profiling and antioxidant evaluation of three Indonesian orange varieties

Abstract

The orange peel contains bioactive components with health−promoting effects, a rich source of antioxidants, and could be used for functional food. However, due to many factors, the composition and concentration of bioactive compounds from orange peels differ because of their variety. This study aims to identify the metabolite and evaluate the antioxidant activity of peels from Indonesian orange varieties, i.e., Rimau Gerga Lebong (RGL, Bengkulu), Brastagi (JBM, North Sumatra), and Garut (JSG, West Java). The metabolite profile was analyzed using LC−MS/MS and discriminated based on orange variety using principal component analysis (PCA) and hierarchical clustering analysis (HCA). Antioxidant activity was measured using the 2,2 −diphenyl− 1 −picrylhydrazyl (DPPH), cupric ion−reducing antioxidant capacity (CUPRAC), and ferric−reducing antioxidant power (FRAP) methods. In this study, the metabolite profile of orange peel proved to be rich in flavonoids like hesperidin, rutin, nobiletin, polyphenol−organic acids like p − coumaric acid, citric acid, quinic acid, and other metabolites from the class terpenoids, amino acids, and sugars. PCA separated each variety and HCA heatmaps showed variations in the distribution of identified metabolites. In the RGL variety, 47 metabolites were identified, dominated by flavonoids and terpenoids. As many as 44 metabolites in the JBM variety contain many amino acids and flavonoids. In JBM, 44 metabolites were identified with carboxylic and amino acids as the main compounds. RGL orange peel extract had the highest antioxidant activity using the DPPH and CUPRAC methods, whereas the FRAP method did not show significant differences. Regarding metabolites and antioxidant activity, RGL, JBM, and JSG orange peels can be developed as alternative functional foods.