Comparative study of the nutritional and bioactive compounds content of four walnut (Juglans regia L.) cultivars

• Chemical composition and bioactive compounds in 4 walnut cultivars were studied.
• Melatonin, serotonin and total polyphenols were determined.
• Significant differences among cultivars were observed.
• Howard cv. showed the highest content in the n−3 acid α-linolenic.

The proximate and mineral composition, fatty acid profile, total polyphenol, melatonin and serotonin contents were assessed in four walnut (Juglans regia L.) cultivars (cv. Serr, Hartley, Chandler and Howard). The aim was to decide which cultivar is the most suitable from a nutritive, but also commercial, point of view. Proteins and fats accounted for more than 70% of the walnut kernel weight. Due to their content in bioactive compounds such as melatonin, serotonin and total phenols, their high content in magnesium (up to 443 mg 100 g−1 FW) and other minerals, their high contents in polyunsaturated fatty acids (up to 78.0% of total fatty acids) and their favorable n−6/n−3 ratio, among other healthful properties, consumption of all the studied cultivars would be potentially beneficial to health. According to its fatty acid profile, Howard would be the most healthful cultivar, but also it would be theoretically the most sensitive to rancidity, and thus the cultivar with the shortest shelf life. Nonetheless, this cultivar showed the highest content in the antioxidants melatonin and total polyphenols.