Studies On The Determination Of Flavonoids And Vitamin C In Citrus Fruits

Many bioactive constituents abound in citrus fruits, such as hesperidin, naringin, hesperetin, neohesperidin, nobiletin and tangeretin, could promote health and prevent disease to human’s body, which led to high pharmacological and economic values.This dissertation based on the determination research of flavones, total flavonoid and vitamin C from citrus fruits, could be divided into the three parts:Firstly, a RP-HPLC method for separation of hesperidin and naringin was established. A C18 column was used and UV detection at 283nm, with methanol or acetonitrile as mobile phase. The effects of mobile phase composition were investigated. A better resolution between the 2 compounds was observed with acetonitrile-THF as mobile phase than that with methanol-ethanol as mobile phase; The hesperidin and hesperetin in citrus peel were determined by RP-HPLC. The method was developed with Bondclone C18 column and UV detection at 283. A gradient elution with water-acetonitrile as mobile phase in flowrate of 1.00mL/min was used; HPLC was performed with methanol（36%）-water（64%） as a mobile phase, the detection wavelength was at 283nm. The neohesperidin was obtained by orthogonal test and extracted with methanol by ultrasound; Nobiletin and tangeretin were extracted with methanol by ultrasound-assisted through single-factor and orthogonal experiment, and were determination by HPLC.Secondly, total flavonoid in citrus peels was determined by UV spectrophotometry at 271 nm using rutin as the standard compound. The extraction conditions of total flavonoid from citrus peels were compared by ultrasonic and microwave assistance with the uniform design method, with respects of power, extracting time, ethanol concentration, ratio of material to liquid as the investigated factors, and it was found that the microwave extraction rate was higher than ultrasound-assisted extraction rate in the tested experimental conditions. The chosen extraction condition of microwave method was as follows: microwave power 390W, extracting time 7 minutes, 50% ethanol, and ratio of material to liquid 1:45（g/mL）.Thirdly, the method is based on the reduction of Cu^{2 +} to Cu⁺ by ascorbic acid and the deposition of CuSCN. The deposited CuSCN was separated off by centrifugalization. Cu in the deposit or in the centrifugate was determined by AAS with the instrumemt default value and the contents of vitamin C in samples were obtained by indirect method. The method is not interfered by the colour of test samples.