Phenolic composition profiling of different edible parts and by-products of date palm (Phoenix dactylifera L.) by using HPLC-DAD-ESI/MSn

Abstract

Fruits and vegetables are an important source of dietary antioxidants and epidemiological studies show that their regular intake in the diet may decrease the risk of several chronic diseases. Phoenix dactylifera L. (date palm or dates) is an important crop, widely used in the Arabian region and in other parts of the world as a food and also in folk medicine, due to its health-promoting properties. Antioxidant phytochemicals present in plant foods are partly responsible for such health benefits. The antioxidants present in dates are mainly phenolics, like flavonoids and phenolic acids. The fruits of dates have been widely studied with regard to their phenolic composition. However, few studies are available in the bibliography regarding other, non-edible parts of the date palm tree. In this context, in the present work the phenolic components of different parts of P. dactylifera (cv. Medjool or Mejhool) - namely, fruit pulp and skin, fronds (leaves), clusters, and pollen - have been investigated using HPLC-DAD-ESI/MSn in the negative ionization mode. The overall analysis of the phenolic compounds revealed that there was a qualitative similarity among the different dates parts analyzed. The method used provided tentative identification of 52 compounds: mainly flavonoid glycosides of quercetin, luteolin, apigenin, chrysoeriol, kaempferol, isorhamnetin, 3-methyl-isorhamnetin, sulfates, and malonyl derivatives. In the present work, more than 30 phenolic derivatives are described for the first time in dates. To the best of our knowledge, kaempferol glycosides and malonyl derivatives have not been described previously in P. dactylifera. The results highlight the importance of P. dactylifera L. as a promising source of functional ingredients and boost its potential use in the food and nutraceutical industries. The MS data, MSn fragmentation pattern, and UV information obtained have been of great help in the interpretation of the compounds detected and in their structural identification.