Over the past few decades, much effort has been devoted to the study of known food products for medicinal applications. Among these, citrus fruits play a key role in providing a wide range of health‐beneficial effects but it generates a huge amount of waste products. In an attempt to recover those wastes, peel of six citrus species (C aurantium, C limetta,C limon, C reticulata, C Sinensis osbeck, and C Sinensis thomson) was evaluated for yield, physicochemical properties, phenolic constituents and antioxidant activities. LC‐MS/MS analysis showed that the flavonoids neoeriocitrin, luteolin‐7‐O‐neohesperidoside, scoparin and neohesperidin were chemical markers for C limetta, whereas apigenin‐6,8‐di‐C‐glycoside was only detected in C Sinensis Osbeck. PCA analysis revealed significant correlations between antioxidant activities and phenolic contents, highlighting a large interspecific variability. These results suggest that Citrus peel by‐products may be valuably recycled by industries due to their high yield and transformed into value‐added products, with potential interest for the development of functional foods, cosmetics or preventive therapies for some diseases.

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Many species from the genus Citrus are used in traditional medicine and contain polymethoxylated flavonoids. These compounds show anti-inflammatory and chemopreventive activities, among others, and therefore have a big potential to be developed as therapeutic agents or dietary supplements. Citrus species are different in their profile and yield of polymethoxylated flavonoids. Therefore, polymethoxylated flavonoids were identified and quantified in seven different Citrus species, including wild-type and commercially available species. All species were profiled using UPLC-QTOF-MS/MS analysis combined with mass spectral molecular networking. A total of 38 polymethoxylated flavonoids were detected and 8 of them were present in every species. As the yield of polymethoxylated flavonoids was different for each species, a generally applicable HPLC-diode array detection method was developed and validated according to the ICH guidelines to quantify the amount of nobiletin and the total amount of polymethoxylated flavonoids expressed as nobiletin. Analysis of the seven samples showed evidence that wild-type Citrus species (e.g., Citrus depressa) contain higher yields of polymethoxylated flavonoids compared to commercially available species (e.g., Citrus limon). Qualitative analysis revealed the broadest variety of different PMFs in C. depressa, Citrus reticulata, and Citrus reticulata × Citrus sinensis, which makes them interesting sources of polymethoxylated flavonoids for future development as therapeutic agents or dietary supplements.

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