Lemon fruits have good nutritional and medicinal values owing to their rich bioactive components such as flavonoids, coumarins, limonoids and phenolic acids. However, the current quantitative analysis methods of bioactive components in lemon fruits have some disadvantages such as the relatively single kind of components or too long detection time. The objective of this study is to establish a rapid and sensitive method to determine the content of multiple bioactive components in lemon fruits, and further compare and analyze the types and contents of bioactive components in different tissues of different lemon varieties, which can provide a reference for evaluating the nutritional quality of lemon and the development of functional products. Based on UPLC-Q-TOF-HRMS and sequential window acquisition of all theoretical fragment ions (SWATH) mode, a rapid and sensitive method was established for the simultaneous determination of 13 flavonoids, 8 coumarins, 2 limonoids and 3 phenolic acids in lemon fruits by using the peak area of characteristic secondary fragment ions with the external standard method. The 26 bioactive components in the peel, pulp and juice of six lemon varieties were further analyzed quantitatively. The method showed good linear relationships, high sensitivity, precision and accuracy. The correlation coefficients of linear equations for all the compounds were more than 0.99. The minimum limit of quantitation (LOQ) was as low as 0.001 μg/L. The interday RSD and intraday RSD were no more than 5.33% and 6.39%, respectively. The recoveries were between (84.27±3.02)% and (114.25±1.77)%. The quantitative results showed that there were great differences in the content of bioactive components in lemon samples of different varieties and parts. The contents of 26 compounds in 6 kinds of lemon fruits were as follows: Keerti Cuningmeng > Lisbon lemon > Eureka lemon > Meiguo Cuningmeng > Bianhong Ningmeng > Meyer Lemon; The contents of the 26 compounds in the peel were significantly higher than those in the pulp and fruit juice. The total contents of flavonoids accounted for the highest proportion of 26 bioactive components, which were the main sources of bioactive components in lemon fruits. Among them, hesperidin was the predominant flavonoid. In addition, limettin, auraptene, and umbelliferone were the coumarins with higher contents in lemon fruits. The method established here for the simultaneous determination of 26 bioactive components based on UPLC-Q-TOF-HRMS and SWATH acquisition mode is suitable for screening and quantitative analysis of multiple types of bioactive components in different parts of lemon fruits. This method is sensitive, reliable and universal, and can be used for the analysis of multiple types of bioactive components in plant-derived products.
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