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Hesperidin and narirutin are a class of flavanone glycosides, which are the main active constituents in Citrus reticulata Blanco. In the present study, a chiral HPLC-UV method with amylose tris(3,5-dimethylphenylcarbamate) as a stationary phase under a normal-phase mode was used to achieve the stereoselective separation of the C-2 diastereomers of hesperidin and narirutin simultaneously. The single epimer was then successfully prepared by applying semi-preparative chromatography, whose absolute configuration ( R / S ) was characterized by combining the experimental electronic circular dichroism (ECD) detection with time-dependent density functional theory (TDDFT) calculations. The epimer composition of these two chiral flavanone glycosides in Citrus reticulata Blanco was then determined, which was found to be slightly different in the herbs from different production regions. The anti-inflammatory activity of each prepared single epimer was further evaluated, and some differences between one pair of epimers of hesperidin and narirutin were observed, which suggested that the presence of different epimers should be considered in the quality evaluation and control of natural medicine.

1,2-Rhamnosyltransferase (1,2RhaT) catalyzes the final step of production of flavanone neohesperidoside (FNH) that is responsible for the primary bitter taste of citrus fruits. In this study, species-specific flavonoid profiles were determined in 87 Citrus accessions by identifying eight main flavanone glycosides (FGs). Accumulation of FNHs was completely correlated to the presence of the 1,2RhaT gene in 87 citrus accessions analyzed using a novel 1,2RhaT -specific DNA marker. Pummelo ( Citrus grandis ) was identified as the genetic origin for a function allele of 1,2RhaT that underpinned FNH-bitterness in modern citrus cultivars. In addition, genes encoding six MYB and five bHLH transcription factors were shown to coexpress with 1,2RhaT and other flavonoid pathway genes related to FNH accumulation, indicating that these transcription factors may affect the fruit taste of citrus. This study provides a better understanding of bitterness formation in Citrus varieties and a genetic marker for the early selection of nonbitterness lines in citrus breeding programs.

Inhibiting microglial activation-mediated neuroinflammation has become a convincing target for the development of functional foods to treat neurodegenerative diseases. Tangerine peel (Citri reticulatae pericarpium) has potent anti-inflammatory capacity; however, its anti-neuroinflammatory capacity and the corresponding active compounds remain unclear. To this end, the composition of a tangerine peel ethanolic extract was analysed by LC-MS, and the anti-neuroinflammatory ability was evaluated using a lipopolysaccharide (LPS)-activated BV2 microglia culture system. Hesperidin is the most predominant flavonoid in tangerine peel, followed by tangeretin and nobiletin. Among the eight tested flavanone glycosides and polymethoxy flavones, only nobiletin displayed a capacity of>50% to inhibit LPS-induced proinflammatory NO, TNF-α, IL-1β and IL-6 secretion at a concentration of 100 μM. At 2 mg/ml, tangerine peel extract attenuated LPS-induced NO, TNF-α, IL-1β and IL-6 secretion by 90.6%, 80.2%, 66.7%, and 86.8%, respectively. Hesperidin, nobiletin, and tangeretin individually (at concentrations of 135, 40, and 60 μM, respectively) in 2 mg/ml tangerine peel extract were only mildly inhibitory, whereas in combination, they significantly inhibited LPS-induced proinflammatory cytokine expression at levels equal to that of 2 mg/ml tangerine peel extract. Overall, tangerine peel possesses potent anti-neuroinflammatory capacity, which is attributed to the collective effect of hesperidin, nobiletin, and tangeretin., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Flavonoids-enriched tissues of citrus such as peel, immature fruit and flower are consumed as culinary seasonings, tea ingredients in China for centuries. This HPLC quantitative study on the five citrus flavonoids, naringin, hesperidin, neohesperidin, sinensetin and nobiletin on a wide range of Chinese citrus fruits and several Traditional Chinese Medicinal food ingredients in East China, revealed a great diversity in flavonoid composition. Huyou peel (C. paradisi cv. Changshanhuyou)was found to be the best naringin (3.25%) and neohesperidin (2.76%) source; C. aurantium, a major ingredient of several citrus-related TCM, is also a suitable source of naringin and neohesperidin, and a good juice source for flavanone glycosides; the peel of Wenzhoumiju (C. unshiu) is one of the richest local species in hesperidin (up to 6.25%); Zaoju (C. subcompressa) has the highest content of nobiletin (0.59%), a polymethoxylated flavone. LC-ES-MS analysis of Zanthoxylum genus for flavonoids revealed for the first time the presence of significant amounts (0.74%) of hesperidin in the root of Liangmianzhen (Z. nitidum (Roxb.) DC), a relative of Sichuan pepper, which is a spice widely used in China. [ABSTRACT FROM AUTHOR]