Quality Profiling and Estimation of Total Phenols, Flavonoids, Flavonols and Antioxidative Potential of Walnut Kernel (Juglans regia) from Kashmir Valley

Present research study was carried out with four walnut (Juglans regia L.) genotypes viz. KG (Kulgam), CS (Char-e-Sharief), KW (Kupwara) and TM (Tangmarg) from major walnut producing areas of Kashmir valley. The aim of the study was the selection of superior genotypes having better quality nuts and kernels with higher antioxidant potential. Nut and kernel quality traits were recorded. The results revealed that the nut weight ranged between 11.70 to 14.51g; nut diameter between 9.60 to 14.27mm; nut length between 17.40 to 20.51mm. The maximum variability was observed in nut weight, kernel weight, nut length and nut diameter. The fat content accounted for more than 60% of walnut kernel weight and ranged between 49.83 to 83.76%.  The antioxidant potential, proximate and mineral composition, total phenolic content, flavonoids, as well as, flavonols, were all evaluated. Mineral content; zinc (Zn), iron (Fe), manganese (Mn), copper (Cu) and magnesium (Mg) were also determined. The total phenolic content varied between 19.8 to 50.19mgGAE/g while the total flavonoid and flavonols ranged from 188.5 to 815.08mgQE/100mg and 3.46 to 7.77mgQE/g, respectively. The walnut extracts (0.5mg mL-1) showed 82.60 to 97.19% DPPH (2,2-diphenyl-1-picrylhydrazyl) scavenging activity. This study demonstrates that owing to maximum nut and kernel weight, better free radical scavenging properties and higher phenolic profile of KW (Kupwara), this genotype seems to have a potential for production on large scale in Kashmir area.