The Effect of Rootstocks on the Peel Phenolic Compounds of Satsuma mandarin (Citrus unshiu)

The aim of this study was to determine total flavonoids and individually flavanone glycosides as well as antioxidant capacity in peel of Satsuma mandarin(Citrus unshiu) on different rootstocks.  On other hand, the purpose of this study was to identify the rootstock that could produce the highest amount of flavonoids.Total flavonoids content was measured using aluminum chloride colorimetric method, whereas Folin-Ciocalteau colorimetric method was used to determine the total phenols content. The antioxidant activities were evaluated using reducing scavenging assays of DPPH radicals. HPLC-PDA detection was used for the analysis of individual flavanone glycosides (narirutin, naringin and hesperidin).The results showed that, the highest individually flavanone glycosides (27.73 mg/g DW), total flavonoids (10.74 mg/g DW), total phenol (3.91 mg/g DW) and DPPH scavenging activity (60.00 mg/g DW) were in the peel of Satsuma mandarin grafting on the flying dragon rootstock. According to results, the amount of phenolic acids (0.36 mg/g DW) of Satsuma mandarin grafted on trifoliate orange was higher than those of other rootstocks. Among the flavonone glycosides, hesperidin was determined in the highest concentration in all investigated peels. The results of correlation showed that there were a high positive correlation between the amount of total flavonoids and total phenols. Results showed that rootstock had an important role in increasing of concentration flavonoids, as well as antioxidant capacity. Finally based on the obtained results it can be concluded that although the concentration of flavonoid compounds is strongly related to the genotype of fruit, it seems that rootstocks affect the amount of flavonoids in the fruit.