Full Length Research Paper
Walnut leaves constitute a good source of healthy compounds, namely phenolics, suggesting that it could be useful in the prevention of diseases in which free radicals are implicated. In this study walnut (Juglans regia L.) leaves from eleven different cultivars (Mayette, Fernor, Mellanaise, Elit, Orientis, Lara, Hartley, Franquette, Parisienne, Arco, Marbot) were studied for their phenolic compounds. The evolution of major phenolic compounds was monitored from May to September. Two extractive procedures were assayed and the best results were obtained using acidified water (pH 2) and a solid phase extraction column purification step. Qualitative analysis was performed by HPLC-DAD/MS and, in all samples; nine phenolic compounds were identified (3-caffeoylquinic, 3-p-coumaroylquinic and 4-pcoumaroylquinic acids, quercetin 3-galactoside, quercetin 3-arabinoside, quercetin 3-xyloside, quercetin 3-rhamnoside, quercetin 3-pentoside and kaempferol 3-pentoside). Quantification of phenolic compounds was performed by HPLC-DAD, which revealed that the highest content of phenolics was found in May and July the quercetin 3-galactoside was always the major compound while 4-pcoumaroylquinic acid was the minor one. In addition, Franquette cultivars total phenolic content was the highest among all cultivars.