Background Intercropping is often used in the tea producing areas where land resources are not so abundant, and the produced green tea is tasted more delicious through a tea-Chinese chestnut intercropping system according to the experience of indigenous farmers. The length and weight of tea leaf increase under this intercropping system and their root systems are stratified vertically and coordinate symbiosis. However, the delicacy mechanism under the intercropping is not fully understood. Results Green tea from the Chinese chestnut–tea intercropping system established in the 1980s ranked highest compared with a pure tea plantation from the same region. Based on the non-targeted metabolomics, 100 differential metabolites were upregulated in the tea leaves from intercropping system relative to monoculture system. Twenty-one amino acids were upregulated and three downregulated in response to the intercropping based on the targeted metabolomics; half of the upregulated amino acids had positive effects on the tea taste. Levels of allantoic acid, sugars, sugar alcohols, and oleic acid were higher and less bitter flavonoids in the intercropping system than those in monoculture system. The upregulated metabolites could promote the quality of tea and its health-beneficial health effects. Flavone and flavonol biosynthesis and phenylalanine metabolism showed the greatest difference. Numerous pathways associated with amino acid metabolism altered, suggesting that the intercropping of Chinese chestnut–tea could greatly influence amino acid metabolism in tea plants. Conclusions These results enhance our understanding of the metabolic mechanisms by which tea quality is improved in the Chinese chestnut–tea intercropping system and demonstrate that there is great potential to improve tea quality at the metabolomic level by adopting such an intercropping system.

Ultrasonic-assisted extraction of flavonoids from Camellia fascicularis leaves was optimized using response surface methodology. The optimal extracting conditions of flavonoids were determined to be the ratio of liquid to raw material of 60 mL/g, ethanol concentration of 40%, extraction temperature of 72.3°C, and extraction time of 1.6 h, which contributed to the highest flavonoids yield of 4.765%. The crude flavonoids were purified through an AB-8 macroporous adsorption resin column, eluted with ethanol concentration of 40%, and purified flavonoids were obtained. In vitro antioxidant assay demonstrated that purified flavonoids showed significant antioxidant capacities in a concentration-dependent manner for scavenging hydroxyl radical, superoxide anion radical, 2,2-diphenyl-1-picrylhydrazyl radical, and azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt radical. Overall, ultrasonic-assisted extraction was found to be an effective method of extracting flavonoids from C. fascicularis leaves, which might be explored as potential natural antioxidant.Capacidad antioxidante de flavonoides obtenidos de hojas de Camellia fascicularis mediante su extracción asistida por ultrasonido RESUMEN Mediante el uso de la metodología de superficies de respuesta (MSR) se optimizó la extracción de flavonoides obtenidos de hojas de Camellia fascicularis asistida por ultrasonido. Al respecto, se estableció que las condiciones óptimas para la extracción de flavonoides son: ratio de líquido a materia prima de 60 mL/g, concentración de etanol de 40%, temperatura de extracción de 72,3°C y tiempo de extracción de 1,6 horas; a partir de estas condiciones se determinó que el máximo rendimiento de los flavonoides es 4,765%. Empleando una columna de resina de adsorción macroporosa AB-8 se purificaron los flavonoides crudos, siendo posteriormente eluidos con etanol en una concentración de 40%. El ensayo mediante antioxidante in vitro demostró que, dependiendo de su concentración, los flavonoides purificados tienen capacidades antioxidantes significativas para eliminar radicales de hidroxilo, anión superóxido, DPPH y ABTS. En general, se constató que la extracción asistida por ultrasonido constituye un método eficaz para la extracción de flavonoides de hojas de C. fascicularis, los cuales pueden ser sometidos a investigación como un potente antioxidante natural.

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