The objective of this study was to evaluate kernels of different pecan (Carya illinoinensis) cultivars for their antioxidant capacity and characterize the nature of the antioxidant compounds. Nuts collected from four pecan cultivars `Cheyenne', `Cape Fear', `Desirable', and `Pawnee' were shelled, chopped and analyzed for their antioxidant capacity (AC), and for their phenolic, tannin, and vitamin C content. AC was measured using one spectrophotometrical [DPPH (2,2-diphenyl-1-picrylhydrazyl)] and one fluorescence method [ORAC (Oxygen Radical Absorbance Capacity)]. Total phenolic and tannin content were determined using spectrophotometrical assays. Finally, ascorbic and dehydroascorbic acid were determined using a high performance liquid chromatograph. Both AC methodologies, DPPH and ORAC, gave similar results with marked differences between cultivars. `Desirable' had the highest antioxidant capacity (47,747 μg TEq/g DW with DPPH method) followed closely by `Cheyenne' (36,192 μg TEq/g DW) and, with smaller amounts, by `Cape Fear' and `Pawnee' (16,540 and 13,705 μg TEq/g DW, respectively). Total phenolic content showed a similar trend but `Pawnee' showed a higher phenolic content than `Cape Fear'. `Cheyenne' had the highest amount of tannins, 9,114 μg/g DW, followed by `Cape Fear', `Pawnee' and `Desirable' with 7,764, 6,043 and 5,508 μg/g DW respectively),. `Cheyenne' had also the highest vitamin C content, up to ≈10-fold greater than `Cape Fear' and `Pawnee', the highest difference within the antioxidants analyzed. There is the need to determine the phenolic profile and degree of polymerization of tannins, their contribution to the AC and how they are affected by horticultural practices in order to better understand the nutraceutical potential of each cultivar.
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