Exploring efficient preparation, biological activities and potential growth-promoting functions of peanut shell flavonoids

Peanut shells, which are agricultural waste of global peanut processing, are rich in flavonoids with bioactive properties such as antioxidant and antimicrobial properties, but their utilization is not enough because of lack of preparation technology suitable for industrial production and investigation for developing application. The aim of this study was mainly to develop a method for high efficiently extraction of flavonoids from peanut shells (PSFs), evaluate the stability, antioxidant activity and antibacterial activity of PSFs, and further investigate its influence on the growth and yield of peanut based on the properties of PSFs. The result showed that the content of flavonoids obtained by ultrasonic-assisted grading extraction can reach 52.06 ± 0.26 %, which significantly higher than traditional alcohol extraction process, thereby the purification process of flavonoids can be greatly reduced. The dominant components (relative content >1%) of PSFs included 9 kinds of flavonoid compounds after purification. PSFs also presented good stability and antioxidant activity, and extensive antibacterial activity, especially, displayed an obvious inhibitory effect on peanut pathogens, such as A. flavus , F. oxysporum , S. rolfsii and other filamentous fungi, which provided a theoretical basis for its application in promoting plant growth and disease resistance. Field experiments showed that the application of PSFs could promote the growth and emergence rate of peanut seedlings, improve root nodulation, and increase peanut yield. The emergence rate and yield of peanut were increased by about 10 % and 20 %, respectively. These findings provide a useful direction on PSFs for its efficient preparation and application into agriculture. • PSFs were enriched by grading extraction combined with pH-regulated purification. • PSFs had good stability, antioxidant activity and excellent antibacterial activity. • PSFs could promote the growth, emergence rate, nodulation, yield of peanut.