Flavonoid and essential oil components in six cultivars of Citrus reticulata in Jiangxi province

Abstract:【Objective】Flavonoids are important functional components in Citrus reticulata, and have been used to treat cardiovascular disease, cancer and other diseases. There are many kinds of flavonoids in different citrus varieties. Essential oils are extracted from plants with aroma. They are rich in the oil chamber in the citrus peel. They have significant effects of expectorant and analgesia, as well as antitussive and anti-inflammatory effects.‘Nanfeng'tangerine lines, such as small fruit line, large fruit line and early line, ‘Xinyu'tangerine, ‘Sanhuhong' angerine and‘Zhangtouhong'tangerine are the primary Citrus reticulata varieties cultivated in Jiangxi province. In the present study we analyzed the chemical compositions and contents of flavonoids and essential oils in these six varieties. The results would be a good reference for comprehensive use of C. reticulata in Jiangxi province.【Methods】The tangerine samples were all collected at 90% full maturity. An Agilent 1260 high performance liquid chromatography (HPLC) system was used to measure the flavonoids in the samples with neohesperidin, hesperidin and naringinused as standards. The HPLC system included a degasser, an autosampler, a quaternary pump and a column heater with a WATERS C18column (4.6 mm×250 mm, 5 μm) ; the mobile phase was acetonitrile and % acetic acid solution; chromatography separation was performed at 40 ℃ with a flow rate of 1.0 m L·min^-1, a sample volume of 10 μL and a detection wavelength of 283 nm. The components were identified by retention time and quantitated by peak area using external standards. The oven-dried samples were degreased by Soxhlet extraction, and 0.1 g of sample was transferred into a 50 mL centrifuge tube, to which10 mL 65% methyl alcohol was added, and ultrasonic extraction was performed at 35 ℃ and 170 W for 40 min. The extract was centrifuged at a low speed of 4 000 r·min^-1for10 min. The procedure was repeated, and the supernatant from the two centrifuges were combined and adjusted to 25 mL in a volumetric flask.The extract was filtrated through a 0.22 μm filtration membrane before loaded to HPLC for measurement of flavonoids. Essential oils were extracted using stream distillation from the peel. The extraction time was4 hours, and the ratio of material to liquid was 1∶3. The gas chromatography-mass (GC-MS) was employed to determine the volatile constituents in essential oil extract. The components were identified using a database and the relative contents of chemical components of essential oils were quantified using the method of peak area normalization.【Results】The results showed that hesperidin was the major flavonoid in different cultivars and fruit parts. The content of hesperidin in the pulp was lower than in the peel. Hesperindin content in the peel was in the order of‘Nanfeng'tangerine large fruit line >‘Nanfeng'tangerine early line >‘Zhangtouhong'>‘Nanfeng'tangerine small fruit line >‘Sanhuhong'>‘Xinyu'tangerine. But in pulp, it was‘Nanfeng'tangerine early line >‘Sanhuhong'>‘Nanfeng'tangerine small fruit line >‘Xinyu'tangerine >‘Zhangtouhong'>‘Nanfeng'tangerine large fruit line. Totally 30 compounds were found in the six cultivars. The number of essential oils contributing to flavor in‘Nanfeng'tangerine large fruit line, ‘Nanfeng'tangerine small fruit line, ‘Nanfeng'tangerine early line, ‘Xinyu'tangerine, ‘Sanhuhong', and‘Zhangtouhong'was 20, 19, 11, 19, 13 and 13 respectively, and terpene hydrocarbons were the dominant substance in essential oils with a relative content of 85.955%, 97.259%, 99.176%, 98.535%, 99.776% and 99.224%, respectively. Among them, terpinenes was the most abundant essential oil component in‘Nanfeng'tangerine early line, accounting for 38.258%. In other cultivars, D-limonene was the most abundant component, which could be up to 80%.【Conclusion】C. reticulata peel has abundant aromatic essential oils and hesperidin. There are differences in the compositions of hesperidin and essential oils among citrus varieties.