Comprehensive analysis of polyphenols from hybrid mandarin peels by SPE and HPLC-UV

Abstract

Polyphenol compounds are the most important bioactive components in citrus peels. An efficient clean-up method based on solid-phase extraction with C18 cartridges (SPE-C18) and high-performance liquid chromatography, coupled with ultraviolet detector (HPLC-UV) determination, was set up for the analysis of phenolic composition in ultrasound assisted extraction from hybrid mandarin (Citrus reticulata) peels (Clemenvilla, Nadorcott, Ortanique). The SPE-C18/HPLC-UV method was validated according to linearity (R2 ≥ 0.998), good precision (intra-day and inter-day), relative standard deviations (<5% in most cases), low limits of detection and quantitation, adequate recovery, and low matrix effect. Eight flavonoids and seven phenolic acids were separated and determined in a single chromatographic run. Ultra-high-performance liquid chromatography, coupled with quadrupole-time-of-flight-mass spectrometry (UPLC-qTOF-MS/MS), was used to confirm the polyphenols previously detected. Results showed that hesperidin and narirutin were the most abundant phenolic compounds in the three hybrid mandarin peel extracts. This study describes an affordable, suitable method for identifying and quantifying phenolic compounds in hybrid mandarin peels. The correlation and analysis of the principal components also showed the main differences between the varieties analysed. There were clear differences between Clemenvilla and Nadorcott and Ortanique, due to the significantly lower narirutin concentration (P < 0.05) in the case of Clemenvilla.