Changes in fruit anthocyanins, their biosynthesis-related enzymes and related genes during fruit development of purple and yellow passion fruits

Together with other polyphenols and flavonoids, anthocyanins have the capacity to serve as free radical scavengers against detrimental oxidants including reactive oxygen and nitrogen species. Moreover, the role of anthocyanin pigments as natural fruit colorings is quite common. In this study, the anthocyanin profile of purple and yellow passion fruit was determined at five developmental phases i.e., fruitlet, green, veraison, maturity, and ripening stage. Total flavonoids were abundantly found among other metabolites including anthocyanins and proanthocyanins. Purple passion fruits contained more than 2-times higher flavonoid content than yellow passion fruits at ripening stage. The findings showed that fruit maturation increased the amount of total flavonoids, anthocyanins, and procyanidins in the pulp of both varieties of passion fruit. Correlation analysis revealed that the passion fruit anthocyanin metabolism may be regulated by the enzymes C4H, 4CL, CHS, UFGT, and GST. The metabolism of anthocyanins in passion fruit may be significantly influenced by the genes PePAL4, PeCHS1, and PeGST7. New information from this work will help future research into the fundamental processes controlling the production of anthocyanins in passion fruit.