Folate levels and polyglutamylation profiles of papaya (Carica papaya cv. Maradol) during fruit development and ripening.

Folates are essential micronutrients for humans, and their deficiency causes several detrimental effects on human health. Papaya fruit is an important natural source of some micronutrients. This paper presents a first complete characterization of folate derivatives accumulated in cv. Maradol papaya during fruit development and ripening processes. During postharvest ripening, the fruit accumulated up to 24.5% of the daily folate recommended dietary allowance (RDA) for an adult in a 1 cup (145 g) portion. Tetrahydrofolate (THF) and 5-methyl-THF were the predominant folate classes observed. Surprisingly, an unusually long polyglutamylation profile of tentatively up to 17 glutamates linked to 5-methyl-THF was detected; to the authors' knowledge, this very long polyglutamyl tail has not been reported for any organism, and it is probably characteristic of this plant species. This polyglutamylation degree changed throughout fruit development and ripening, showing the largest differences at the onset of ripening. This work raises questions about the functional role of folate derivatives in fruit development.