RP-HPLC–DAD-ESI-TOF–MS based strategy for new insights into the qualitative and quantitative phenolic profile in Tunisian industrial Citrus Limon by-product and their antioxidant activity

Citrus by-products are an important source of bioactive constituents, such as organic acids and phenolic compounds, with health promoting and nutritive properties. To increase our knowledge about this topic, the aim of the present study was to undertake a comprehensive characterization and quantification of major bioactive compounds in Citrus limon by-product dried powder (CBP) proceeding from a Tunisian company using reversed-phase high performance liquid chromatography (RP-HPLC) coupled to electrospray ionization time-of-flight mass spectrometry (ESI-TOF–MS) operating in negative ion mode. Physicochemical properties and the antioxidant activity of CBP were also assessed. As a result, 38 phenolic compounds including 6 phenolic acid derivatives, and 32 flavonoids were characterized and quantified. This work was complemented by the detection of 2 organic acids. To the best of our knowledge, 6 phenolic compounds have not previously been recorded in CBP. In this regard, the main flavonoids in CBP were the flavanones hesperetin 7-O-rutinoside, eriodictyol 7-O-rutinoside, and hesperetin 7-O-neohesperidoside followed by the flavones diosmin. Moreover, the dimer of caffeic acid-O-hexoside was the major phenolic acid. In addition, these results suggested that the extract obtained from CBP had an interesting antioxidant activity comparable with synthetic antioxidants and showed also high amounts of dietary fiber, protein, total sugars, and carotenoids. Finally, the results obtained in this work confirmed that the CBP is a good source of bioactive compounds and the isolation of antioxidant nutraceuticals could be an advantageous way to revalorize these by-products for potential use as dietary additives in functional foods and cosmetics as well as in pharmaceutical industry.