Clean recovery of flavonoids from citrus peel: studying lipid-flavonoid interactions as a tool for understanding the antioxidant activity

Due to its high flavonoids content, citrus peels could be successfully exploited by both pharmaceutical and food industries. It is therefore important to characterize structurally the compounds present in raw material [1]. In the present work, we report the use of an aqueous free-solvent ultrasound-assisted method for flavonoid fraction recovery from orange, lime and tangerine peel produced in tropical South America cultivars. We confirmed the presence of hesperidin, neohesperidin, isorhoifolin, diosmin, tangeritin and nobiletin by HPLC/ESI//MS/MS. The effect of flavonoid fractions and their most abundant compounds on the peroxynitrite-induced oxidation of low density lipoprotein (LDL) was also evaluated. At 10µg/mL, all flavonoid fractions inhibited more than 95% oxidation of LDL. In order to understand the interaction between flavonoids and lipids, we investigated the behaviour of the flavanone glycoside hesperidin and its aglycone hesperetin in dimyristoylphosphatidylcholine (DMPC) vesicles. Differential scanning calorimetry (DSC), atomic force microscopy (AFM), fluorescence measurements using merocyanine 540 as a probe and computational modelling (Gaussian 98 Level B3LYP/6–31G), were used as instrumental tools. We found that hesperidin, but not hesperetin, modified the temperature of DMPC pre-transition, decreased the phospholipid bilayer height and increased its fluidity. Through a theoretical study, it was observed that hesperidin, due to its rutinoside moiety, is located at the level of polar head whereas hesperetin interacts better with acyl chains and adopts a more planar conformation.

Acknowledgements: This work was funded by COLCIENCIAS grant.

References: 1. Mata-Bilbao, et al. (2007) Food Chem 101: 1742–1747.