| Kumquat is native to China, which is a genus of Fortunella and a relative of citrus, both belonging to the Rutaceae family, a group of small fruit-bearing trees. The main varieties of kumquat are Luofu (F. margarita), Luowen (F. japonica), Jindan (F. crassifolia), Jindou (F. hindsill) and other kumquat (intergeneric hybrid). The main cultivars of kumquats in China are Luofu, Luowen and Jindan. As one of the most important fruit crop, kumquat is mainly grown in Ningbo of Zhejiang province, Liuyang and Lansan of Hunan province, Suichuan of Jiangxi province, Rongan and Yangshuo of Guangxi province, Youxi and Sanming in Fujian province, Jiangjin of Chongqing, Yichang and Zigui in Hubei province etc. The current annual production of kumquat reached to 0.25 million tons and the cultivated area and yield are the highest in the world.A large number of epidemiological and animal studies showed that citrus fruits have antioxidant activity, anticancer, prevention of circulatory system disease, anti-inflammatory, anti-allergic and antibacterial effect owe to the abundant physiological active ingredients and nutrients such as Vc, flavonoids, carotenoids, phenolic acids, limonin, volatile components, amino acids and coumarins etc.Unfortunately, there were a few reports on the separation and identification of the functional and nutrients components kumquat home and abroad. And the most studies were foused on single component. It has been no report on the comparation between different varieties of kumquat. In this paper, the content of major nutrient components (Vc, minerals elements, soluble solids, titratable acidity, free form amino acids) and functional components (flavonoids, phenolic acids, limonoids, carotenoids and volatile components) of 15 different kumquat varieties in China were studied. The results obtained were compared and analyzed to provide more useful information for the utilization of varieties resources, the development of nutrition and functional component database, the identification and auxiliary validation of species and the exploitation of health food and drug. The main results were presented as follows:1. This study had optimized and developed the methods for the determination of flavonoids, phenolic acids, carotenoids, limonins in kumquat:(1) The study had developed a UPLC-PDA-MS/MS method for the determination of eleven flavonoids (hesperidin, neohesperidin, rhoifolin, poncirin, fortunellin, phloretin 3’,5’-di-C-β-glycopyranoside, apigenin 8-C-rutinoside, apigenin-6,8-di-C-glycopyranoside, margaritene and isomargaritene) in kumquat varieties. Results showed that 10 flavonoids were separated within 16 min. And the methodology validation had been passed.(2) The study had optimized a HPLC method for the determination of six phenolic acids (coumaric, chlorogenic, caffeic, p-coumaric, ferulic and sinapic acids) in kumquat varieties. Results showed that 6 phenolic acids were separated within 20 min. And the methodology validation had been passed.(3) The study had optimized a HPLC method for the determination of five carotenoids (lutein, zeaxanthin, p-cryptoxanthin, a-carotene and β-carotene chlorogenic) in kumquat varieties. Results showed that 5 carotenoids were separated within 40 min. And the methodology validation had been passed.(4) The study had optimized a HPLC method for the determination of two limonoids in kumquat varieties. Results showed that 2 limonoids were separated within 15 min. And the methodology validation had been passed.2. Analysis of the main nutrient components of different varieties of kumquat in China and their differences. The mineral elements (K, Ca, Mg, Fe, Mn, Cu and Zn) and soluble solids in 15 kumquat varieties were not much different. The total amount of Vc and titratable acidity had larger disparity, with the range from 82.91±2.68 to 3.28±0.10 mg/100g FW and 3.06±0.06 to 0.11±0.002 mg/100g FW, repectively.16 kinds of free-form amino acids were detected. The total contents were in range of 3496.35±0.45 to 1619.99±0.24 mg/100g DW.3. Analysis of the main functional components of different varieties of kumquat in China and their differences.(1) As far as flavonoids in the whole fruit of kumquat were concerned, phloretin 3’, 5’-C-glucoside were highest content in 15 kumquats varieties. The total content of flavonoid in wild kumquat was highest, Hua Pi Jin Gan followed, Da Guo Jin Dou was the lowest. The average content was 9126.69±0.42 mg/kg DW. Except wild kumquat, the total amount of other species were not much different.(2) As far as phenolic acids in the whole fruit of kumquat were concerned, four kinds of phenolic acids were detected, coumaric and chlorogenic acids were not detected. The average content in descending order was p-coumaric acid> erucic acid> phenolic acid>caffeic acid. The total content of phenolic acids in wild kumquat was highest, kumquat hybrids followed, and Ningbo Luo Wen was the lowest.(3) As far as carotenoids in the whole fruit of kumquat were concerned, the average content in descending order was β-cryptoxanthin> lutein> zeaxanthin> β-carotene> a-carotene. The total content of carotenoids in Da Guo Jin Dou was highest, kumquat hybrids followed, and Hua Pi Jin Gan lowest. Except Da Guo Jin Dou and kumquat hybrids, other varieties were about 3-7 times of Hua Pi Jin Gan.(4) As far as limonoids in the whole fruit of kumquat were concerned, the contents of limonin in different varieties were higher than nomilin. The total content of limonoids in Chang Shou Jin Gan was highest, Wen Guang Ju and wild kumquat were second, and Si Ji Ju was lowest. The total contents of all the other kumquats were 1-6 times of Si Ji Ju.(5) The volatile components of several major kumquat varieties from China were investigated and compared. Gas chromatography-mass spectrometry (GC-MS) combined with headspace solid phase microextraction (HS-SPME)was used to determine the contents of volatile components from the peels of 15 different kumquat varieties. A total of 195 volatile substances were detected in all the samples, including terpenes, alcohols and aldehydes. The number of volatile components identified in each variety ranged from 45 to 78, and the total content of volatile components ranged from 791.69 to 27 405.95 μg/g fresh weight with coefficient of variation of 46.46%. The main components were limonene, myrcene, a-terpinene, y-terpinene, isolimonene, terpinolene, a-pinene, y-elemene, a-caryophyllene, germacrene D, a-amorphene and linalool. |
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