Analysis of Volatile Flavor Compounds and Evaluation of Antioxidant Activities in Tender and Mature Leaves of Sweet Tea (Lithocarpus litseifolius)

This study aimed to investigate the volatile flavor compounds and antioxidant activities of extracts from tender leaves (NY) and mature leaves (LY) of Lithocarpus litseifolius. The purpose was to reveal the composition of volatile substances and bioactive characteristics of Lithocarpus litseifolius leaves at different growth stages. Headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS) was used to identify the volatile compounds in NY and LY of Lithocarpus litseifolius. Results showed that a total of 65 volatile compounds were detected in both NY and LY, among which 61 were identified. The main volatile compounds in NY were alkenes (21.85%) and ketones (20.88%), while those in LY were alcohols (24.12%), esters (18.55%), and ketones (18.03%). Principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA) were applied to analyze the differences in volatile compounds. A total of 43 differential aroma compounds were screened out based on VIP values. The release patterns of total phenolic content (TPC) and total flavonoid content (TFC) with brewing times of Lithocarpus litseifolius leaves were explored. It was found that the release of TPC and TFC was mainly concentrated in the first three brews, with a release rate exceeding 90%. During brewing, the release content of TPC in NY was higher than that in LY, while the release content of TFC was lower than that in LY. In addition, Pearson correlation analysis indicated that TFC and TPC had significant effects on the antioxidant capacity of Lithocarpus litseifolius. This study on the characteristic volatile flavor compounds and activities components of NY and LY of Lithocarpus litseifolius provides a scientific reference for the further comprehensive utilization and quality evaluation of Lithocarpus litseifolius resources