Phenolic Acid Composition and Antioxidant Activity of Whole and Defatted Seeds of Italian Hemp Cultivars: A Two-Year Case Study

The study investigated the nutritional profile and nutraceutical composition of the seeds (whole and defatted) of two monoecious hemp cultivars (Carmaleonte, Codimono) and one dioecious cultivar (CS) grown during the 2018 and 2019 crop seasons. The phenolic acid profiles, both free and bound, antioxidant activity (AA), protein content (PC), total phenolic content (TPC), β-carotene, lutein content, and condensed tannins (CT) were studied, and the effects of genotype (G), year (Y), and GxY interaction were also measured. The results indicated the stronger involvement of the year in the nutritional and antioxidant properties of the whole seeds than in those of the defatted seeds, as indicated by the analysis of the variance. The PC, TPC, AA, sum of phenolics free (SPF), and sum of phenolics bound (SPB) were significantly affected by year, while the lutein and some phenolic acids, free and bound (ferulic and p-coumaric acids and N-trans-caffeoyltyramine), showed significant effects of the genotype. In this respect, the Carmaleonte revealed the highest content of ferulic and p-coumaric acids, as well as CS of N-trans-caffeoyltyramine. A prevalence of Y effect over G was measured in the free and bound fraction of the phenolics of the whole seeds, in contrast to the defatted seeds, in which significant effects of GxY were also measured. Moreover, the Pearson’s correlation coefficients indicated a strict involvement of precipitations in the variation of the phenolics accumulation, above all with bound p-hydroxybenzoic acid (r = 0.71 **), bound syringic acid (r = 0.69 *), bound N-trans-caffeoyltyramine (r = 0.64 *), and SPB (r = 0.60 *). As phenolics bound fractions have strong biological activities, (including antioxidant and anti-inflammatory activities) the high concentrations of N-trans-Caffeoyltyramine B in the CS defatted seeds suggest that it is valuable ingredient for functional foods.