Bioactive Compounds Identification And Antioxidant Activity Study Of Five Citrus Fruits Native To China

Among the most important cash crops, Citrus L. is widespread planting in the world. China, the important origin ground of citrus, processes abundant citrus resources. Citrus fruits are rich in bioactive compounds which include flavonoids, limonins, coumarins and so on. These bioactive compounds have powerful anti-oxidant, anti-inflammatory, anti-aging, anti-cancer and anti-Alzheimer‘s disease activities and they are wildly used in foods, medicines and cosmetics. There are many methods and tools to analyze those bioactive compounds. The commonly analytical tools include HPLC, LC-MS, UPLC-Q-TOF-MS. At present, there are few reports on the analysis of bioactive compounds in citrus fruits native to China. Therefore, the aim of the present study is to find a fast analysis method of chemical compositions in citrus fruits, and to evaluate their anti-oxidant activities. In view of the domestic and foreign achievements and shortcomings about the research of compound analysis in citrus, this study will be significant.In this work, the five Citrus fruits native to China were Ponkan, Hongju, Huyou,Liangpingyou, Xiaoxiangyuan.This study identified the bioactive conpounds in thefive citrus fruits using UPLC-Q-TOF-MS and evaluated their anti-oxidant activity bymethods of DPPH, FRAP and ABTS. The main results are as follows:(1) The analytical column was ACQUITY UPLC BEH C18 column. The UPLC chromatographic conditions were optimized to achieve high resolution and best separation. The conditions include column temperature, flow rate and mobile phase. The best conditions were as shown below: column temperature was 40 oC; the flow rate was 0.4 m L·min-1; the mobile phase consisted of 0.01% formic acidsolution(A) and methanol(B) using the following gradientprogram: 0~0.6 min, 90-80% A, 0.6~5 min, 80-30% A, 5~7 min,30~10% A, and 7~8 min, 10-90% A. The analysis method was fast, efficient and accurate. It also can be used in the research of chemical compounds analysis in citrus and their products.(2) This study identified the bioactivity compounds in five citrus fruits by UPLC-Q-TOF-MS. According to the chromatography retention time, UV spectrum, exact molecular weight and high energy fragment ions, combined with information from reference standards or literatures, 43 chemical compounds were unambiguously identified or tentatively characterized. These compounds included 31 flavonoids, 7 limonins, 1 coumarin and 4 other compounds. These results indicate that the identified compositions are difference in the peel and pulp methanol eatracts of different citrus types.(3) The antioxidant activity in five citrus fruits was evaluated by methods of DPPH, FRAP and ABTS. Results showed that the antioxidant capacity of peel was stronger than pulp, except of Liangpingyou.We used the overall antioxidant potency composite index to evaluate the fruits antioxidant activity. In the study of the citrus peel, Ponkan showed the highest antioxidant capacity, the second was Hongju, the worst was Xiaoxiangyuan; in the study of citrus pulp, Ponkan owned the highest antioxidant capacity, the second was Huyou, the worst was Xiaoxiangyuan. In summary, citrus fruits showed stronger antioxidant activities. The study provided theoretical bases for the processing and utilization of citrus fruits.