Revealing the chemical differences and transformations of Artemisia argyi leaves under different processing...

The leaves of Artemisia argyi (AL) with fragrant smell were used as food material as well as traditional Chinese medicine. Processing methods such as stir-frying or stir-frying with vinegar significantly alter the types and contents of chemical components in AL which endow AL unique flavors and effects. However, it is still lack of standard procedure for production of stir-fried A. argyi leaves (SAL) and vinegar-processed A. argyi leaves (VAL) so far, making it hard to guarantee the quality of AL products. Furthermore, the specific mechanisms behind chemical changes remain unclear. In the present study, processing methods for SAL and VAL production were optimized using the Box-Behnken design-response surface method. The effects of these processing methods on both volatile and non-volatile components were investigated using HS-GC-MS and UHPLC-Q/TOF-MS, combined with a metabolomics approach. A total of 73 volatile components were identified and relatively quantified. 18 differential volatile metabolites were screened out with the contents of 15 of them decreased significantly after processing. Three volatile compounds, named 3,7-dimethyl-6-enol, trans-(-)-pinanol and 2-ethenylfuran, were detected in SAL and VAL but absent in AL. Formation of new compounds might be related to the Maillard reaction or pyrolysis induced by elevated temperature during processing. Further, 65 non-volatile metabolites were annotated with the contents of 31 of them significantly changed after processing. Hydrolyzation during processing resulted in a decline of flavonoid glycosides and organic acid glycosides while increase in their corresponding aglycones and organic acids. In conclusion, the optimized processing methods and the findings in chemical alteration of processed AL could provide data support for the application of AL and its processed materials in pharmaceutical products and functional foods.