Analysis and evaluation of antioxidant activity of leaves, flowers and fruits of loquat F1 generation of Ninghaibai and Oobusa

【Objective】Loquat is native to China, and has a long history of cultivation and medicinal use. Loquat phenolic substances, as natural antioxidants, have a variety of biological activities. At present, most studies on loquat phenolic substances and antioxidant activity only focus on single organ such as leaf, flower, and fruit, and lack comparative analysis among the different organs. In addition, the evaluation of the antioxidant activity of loquat mainly involves ranking and evaluating the antioxidant activities measured by different methods, and there are few studies on comprehensive evaluation. In order to provide a theoretical basis for the breeding of new loquat varieties with high total phenolic, flavonoids content and high antioxidant activity, as well as to supply reference for the effectively developing andutilizing of loquat functional ingredients, this study aimed to explore the diversity of total phenolic, flavonoids contents and antioxidant activity in different organs of the loquat F1 hybrid population, and to comprehensively evaluate the antioxidant activity.【Methods】The total phenolic, flavonoids content and antioxidant activity of the different organs of Ninghaibai and Oobusa and their 29 F1 offsprings were determined. The total phenolics content was determined by Folin-ciocalteu method, the flavonoids content was determined by sodium nitrite-aluminum chloride method. DPPH (1, 1-Diphenyl-2-picrylhydrazyl) radical scavenging capacity (DPPH value), ABTS (2, 2'-azino-bis-3-ethylbenzthiazoline-6-sulphonic acid) cation radical scavenging capacity (ABTS value), Ferric reducing antioxidant power (FRAP value) in vitro were determined by DPPH method, ABTS method and FRAP method, respectively. Diversity analysis and correlation analysis were conducted on the total phenolics, flavonoids and antioxidant activity of different organs of the hybrid offspring. In addition, a comprehensive evaluation and cluster analysis were conducted on the antioxidant activity of the hybrid progeny.【Results】There was a rich diversity in the total phenolics and flavonoids contents, as well as antioxidant activity in the different organs of the loquat F1 generations of Ninghaibai and Oobusa. In the leaves, flowers and fruits, the coefficients of variation of total phenolics content were 23.84%, 9.51% and 16.50%, the coefficients of variation of flavonoid content were 49.48% , 13.38% and 44.67% , the coefficients of variation of DPPH value were 23.93% , 15.77% and 17.28% , the coefficients of variation of ABTS value were 26.98%, 13.93% and 21.82%, the coefficients of variation of FRAP value were 25.32%, 11.91% and 20.65% , the coefficients of variation of Antioxidant potency composite (APC) index were 23.85% , 10.43% and 17.42%, respectively. The order of the coefficients of variation in the different organs of the hybrid offsprings was leaves＞fruits＞flowers. Except for the total phenolic content of the flowers, the other traits were widely segregated and had high genetic potential. In addition, there are significant differences in the content of total phenolic, flavonoids content and high antioxidant activity in the different organs of the hybrid offsprings, and the order was flowers＞leaves＞fruits. The antioxidant activity of the different organs was comprehensively evaluated using the APC index, the top three plants with high antioxidant activities in the leaves were ND107, Oobusa and ND128. The top three plants with high antioxidant activities in the flowers were ND164, ND165 and ND082, while the top three plants with high antioxidant activities in the fruits were ND106, Oobusa and ND037. Correlation analysis showed that the total phenolics and flavonoids contents in the leaves and fruits were significantly correlated with the antioxidant activity, while the contents of total phenolics and flavonoids in the flowers were correlated with the antioxidant activity. Moreover, there was a significant positive correlation between the APC index and in vitro antioxidant activities such as DPPH value, ABTS value and FRAP value, but there was no significant correlation between the total phenolics, flavonoids and antioxidant activity in the different organs. The 29 strains of hybrid offspring and their parents were divided into 5 categories by cluster analysis. The first and second groups contained 26 lines, with moderate antioxidant activity. The third group only contained ND080, with weak antioxidant activity in the flowers and fruits. The fourth group only contained ND148, with weak antioxidant activity in the leaves but strong antioxidant activity in the flowers and fruits. And the fifth group contained ND107, Oobusa and ND128, with the strongest antioxidant activity in the leaves.【Conclusion】The diversity of the total phenolic and flavonoids contents and antioxidant activity of the different organs were rich in the F1 generation of loquat Ninghaibai and Oobusa. Except for the total phenolics in the flowers, the total phenolics content, flavonoids content, DPPH value, ABTS value, FRAP value and APC index showed a wide range of segregation and had good genetic potential. The genetic variation of the leaf traits in the F1 generation wasmore abundant than that in the flowers and fruits. There were obvious differences in the total phenolics content, flavonoids content, DPPH value, ABTS value and FRAP value among the different organs of the hybrid offsprings, and the contents in the flowers and leaves were much higher than those in the fruits. The correlation analysis verified that the total phenolics and flavonoids were important antioxidant components in loquat. There was no significant correlation between the total phenols, flavonoids, antioxidant activity in the different organs. The APC index and cluster analysis could be used to screen the hybrid offsprings with strong comprehensive antioxidant activity. The research results could provide a theoretical basis for the scientific configuration of crossing combinations and improve the breeding efficiency, which could also supply a reference for the effective development and utilization of the functional components of loquat.