Integrated GC-MS and LC-MS metabolomics reveals grade-dependent chemical variation and antioxidant activity of Gougunao tea.

Abstract

Gougunao tea (GT), a renowned Chinese green tea, is commercially classified into multiple quality grades, yet the metabolomic basis of grade differentiation and antioxidant potential remains unclear. In the current study, integrated HS-SPME-GC-MS and UPLC-QE-Orbitrap-HRMS metabolomics, chemometrics, and antioxidant assays were used to characterize six commercial GT grades (G1-G6). In total, 137 volatile compounds and 328 non-volatile features were annotated. Alcohols, aldehydes, and ketones dominated the volatile profiles, whereas fatty acid derivatives, flavonoids, amino acids, and peptides were major non-volatile classes. PCA and PLS-DA revealed grade-associated metabolic differences, with 81 features (31 volatile and 50 non-volatile) screened as candidate grade-associated features. GT samples showed strong DPPH, ABTS, and FRAP antioxidant activities, with G6 generally showing better antioxidant performance. Correlation analysis indicated that several flavonoids were positively associated with antioxidant capacity. These findings provide metabolomic evidence for GT grade differentiation and identify candidate chemical features associated with commercial grade.

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