UPLC-ESI-QTRAP-MS/MS identification and antioxidant activity of hawthorn with different infestation levels

This study employed UPLC-ESI-QTRAP-MS/MS metabolomics technology (MRM mode) to analyze two hawthorn varieties infested by Plodia interpunctella (Hüb.) and Tribolium castaneum (Hbst.) at different infestation levels (3 biological replicates per treatment), aiming to investigate the alterations in flavonoid metabolites and their effects on antioxidant activity under different infestation levels. A total of 32 previously characterized flavonoids were identified, covering flavonols, isoflavones, dihydroflavones, flavones, flavanols, dihydroflavonols, and chalcones. The observed flavonoid reduction following infestation aligned with established mechanisms of insect-plant interactions, including potential contributions from both direct feeding and metabolic consumption and associated microbial metabolism. Using screening criteria of P < 0.05 with FC > 1.5 for upregulation or ≤ 0.8 (for downregulation), eight shared differential metabolites strongly associated with insect infestation were identified. Spearman correlation analysis revealed a significant association (P < 0.05) between insect-induced reduction in flavonoid cs and the decline in antioxidant capacity, with this correlation being closely related to the characteristic structural groups of the flavonoid compounds. Epicatechin and genistin were selected as effective markers for characterizing the reduction of antioxidant activity in hawthorn after insect infestation. This study identified significant associations among insect infestation, flavonoid variation, and antioxidant activity in hawthorn. These findings provide insights into the co-occurring changes in nutritional and functional properties during infestation, offering potential indicators for post-harvest quality monitoring.