Alterations in Nonvolatile Components of Tea (Camellia sinensis) Induced by Insect Feeding under Field Conditions

Tea leaf components are affected by environmental factors such as insect feeding, and metabolites have been studied using specific insect and tea leaf model systems. However, in gardens, tea leaves are eaten by various insects. Because the components of tea may affect human health, the effect of insect damage on metabolites needs to be clarified. The aim of this study was to investigate the effects of insect feeding on the nonvolatile components of tea in a field experiment. Furthermore, we determined the effects of insect damage on the composition of black tea products. Tea leaves were sampled from insect-attacked and moderately insect-attacked areas. Catechins were quantified by ultra-performance liquid chromatography. Tea leaves were analyzed by ultra-performance liquid chromatography-mass spectrometry, followed by orthogonal partial least squares-discriminant analysis and molecular networking analysis. The nonvolatile components in insect-attacked leaves were significantly affected. The amounts of gallate-type catechins in highly attacked leaves were approximately 1.2 times higher than in moderately attacked leaves. Furthermore, highly attacked leaves had increased levels of afzelechin gallate, procyanidins, and hydrolyzable tannins. These results varied with previous reports that used model systems with specific insects. In addition, some of these compounds were also detected as characteristic components in black tea from highly attacked leaves.