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Two flavanone glycosides were isolated from the aerial part of Launeae arborescens (Asteraceae), which were identified as hesperidin and naringin. They are the most abundant flavonoids in the edible parts of many species of citrus fruits. In this study, we were interested in the chiral separation and determination of the diastereomerisation barriers of hesperidin and naringin by HPLC methods. The chiral separation HPLC screening of diastereomers of hesperidin and naringin by HPLC methods was accomplished in the normal-phase mode using 11 chiral stationary phases and various n-hexane/alcohol mobile phases. The rate constants and activation energy of diastereomerisation (DeltaG#) of flavanones, naringin and hesperidin were determined, respectively, on Chiralpak IC and Chiralpak IA. The analysis of flavanones isolated in butanol extracts of Launeae arborescens were confirmed by HPLC on Chiralpak IC.

Two broad approaches for the syntheses of a series of 4-aminoflavanes are used in this study, and they have been prepared in 30-99% overall yields using the reductive condensation of flavanone with primary amine, as a key step. By this methodology, the formyl derivatives of several secondary amines were obtained in good to excellent yields. The structures of all new products have been confirmed by spectral experiences (IR, H NMR andC NMR). However, the present non-stereoselective synthesis results in a mixture of 2-7: diastereomers, which differ from the configuration of the flavanone atom asymmetric center. Since each diastereomer may have different biological activity and pharmacokinetic profile, analytical methods have to be developed for their separation. The 4-aminoflavanes diastereomers were separated using polysaccharide chiral stationary phases columns consisting of cellulose (Chiralcel OD-H and ChiralcelOJ) by high-performance liquid chromatography; the separation was affected by the nature and concentration of the alcohol modifiers in the mobile phase. Separations were carried out under normal phase mode on the ChiralcelOJ column. This method can properly separate the two diastereoisomers (Rs > 2) within an analysis time of <50 min.

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