Antioxidant capacity in fruits of cultivar resources of genus Prunus

Abstract: 【Objective】Antioxidant capacity of fruit has been confirmed to improve health and prevent many kinds of cancers and aging-related illness of people. Breeding fruit varieties with high antioxidant capacity is one of the most important aims of breeders. Plums are so riched in chemicals of high antioxidant capacity such as polyphenols and flavonoids that are more and more popular. Evaluaton of the antioxidant level of plum resources is fundamental work for breeding plum varieties with high polyphenols and antioxidant capacity. The aim of our study is to provide basic data for further evaluation of antioxidant capacity of plum resources, and to select plum germplasm resources with high antioxidant capacity and phenolic contents.【Methods】The total antioxidant capacity (TAC) and total phenolic content (TPC) of 59 accessions of plum including 7 Prunus species, that is, P. salicina, P. simonii, P. domesitica, P.americana, P. nigra, P. cerasifera, and P. spinosa, four wild types of P. domesitica and five P. salicina hybrids with different colors were analyzed. All the plum materials were sampled in Chinese Germplasm Repository for Plums and Apricots (Xiongyue town, Liaoning province) in 2015 during ripening period. The flesh (with skin) was separated from kernel, and then was cut up and was mixed. The samples were stored under-80 ℃ in ultra-low temperature freezer. TAC was analyzed using the following 3 methods: 2, 2-diphenyl-1-picrylhydrazyl radical scavenging capacity (DPPH) , trolox equivalent antioxidant capacity (ABTS) and ferric ion reducing antioxidant power (FRAP) . TPC was detected by Folin-Ciocalteau method.【Results】The plum resources had a wide range of TAC and TPC. The range of TAC (DPPH) was 4.58-17.36 μmol·g-1, and the most accessions of the cultivars were in the range of 9-10μmol·g-1. The range of TAC (ABTS) was 4.04-24.17 μmol·g-1, while TAC (FRAP) range was 9.74-75.61μmol·g-1. The TAC (FRAP) value was most in 10-35 μmol·g-1 (43 accessions) . The range of TPC was60.42-469.89 mg· 100 g^-1, and the most accessions (46 accessions) were in the range of 75-250 mg· 100 g-1.‘Meiguoniuxinli'had the highest DPPH and ABTS value among all the samples, and‘wolf'had the highest FRAP. While‘Sloes 1#'had the lowest DPPH and ABTS and‘Loyer'had the lowest FRAP. P.domesitica had the greatest variability among all the species. The highest value of TAC measured by DPPH, ABTS and FRAP, and TPC value were 3.64 times, 3.69 times, 5.59 times and 4.33 times hogher than that of the lowest values separately. It was found in our study that TAC had significant correlation with TPC measured using DPPH, ABTS and FRAP method, with r2 were 0.913, 0.934 and 0.930. P.americana had the highest TPC and TAC while P. domesitica had the lowest, however, the wild types of P. domesitica had igher TPC and TAC which was only lower than those of P. americana. The differences of TPC and TAC between P. salicina and P. salicina hybrids were not significant. The order of DPPH and TPC contents in plums of different colors were: red> purple red> blue black> orange>purple black > green, the ABTS sequences were: red> purple red> orange> blue black> purple black > green, while the order of FRAP were red> purple red> blue black> purple black > orange> green. In our study, TPC and TAC of different colors in different species were also measured. In P. domesitica (including wide type of P. domesitica) , the first two accessions with higher TPC and TAC were blue black and purple black plums, while in P. salicina (including P. simonii and P. salicina hybrid) , the top two accessions with higher were purple red and red, and the green fruits had the lowest level. However, the differences of TPC and TAC among different resources with different colors were not significant. The range of TAC of fruits of P. salicina was 6.90-17.35 μmol·g-1 (DPPH) , 7.23-23.69μmol·g-1 (ABTS) and 12.25-63.64 μmol· g^-1 (FRAP) , while the range of TPC was 86.64-368.28 mg· 100 g-1.The cultivars with high TPC and TAC were‘Beauty'‘Kuili'‘Ziyu'and‘Suili#3', their FRAP values were over 44% higher than the average, and their TPC were over 43% higher than the average. On the other hand, ‘Haichengpingguoli'‘Keyoow'and‘Mutianli'had lower TAC and TPC. TPC of‘Beauty' (368.28 mg· 100 g-1) was about 3.6 times higher than that of‘Haichengpingguoli' (102.28 mg· 100 g-1) .【Conclusion】Plums of different types and species had a wide range of TAC and TPC. Fruits of P. americana had the highest content of TPC and TAC, while fruits of P. domesitica had the lowest. However, the wide type of P. domesitica also had the higher content of TPC and TAC. There was no significant differences in the contents of TPC and TAC among fruits of different colors. But the fruits with dark color skin in the same species had relative higher level of TAC and TPC. In P. salicina, the varieties of‘Beauty'‘Kuili'‘Mili'‘Ziyu'and‘Suili#3'had higher TPC and TAC.