Total phenolic content and antioxidant capacity of hemp co-products after green extraction and ex vivo digestion simulation

The valorisation of biomass generated along the agri-food chain into co-products represent a valid approach to produce alternative and sustainable feed ingredients. Although to date, some co-products have already been included in the diets of farm animals, the characterisation of co-products from hemp and hempseeds (Cannabis sativa L.), is still at an early stage, despite the trend is growing steadily throughout Europe; a tendency that will allow for increased volumes to be allocated to the feed sector. While hemp has already been characterised in the literature, the co-products are still little investigated, especially from a functional point of view. For this reason, the aim of the present research is to study the total phenolic content (TPC, Folin-Ciocalteu) and antioxidant activity (ABTS assay)) of hemp co-products such as panel (HP), leaves/flowers mix (HLs) and hulls (HHs), after green extraction (water: EtOH, W:E) and ex vivo digestion process. For the green extractions, 150mg of samples were incubated for 1h, at room temperature, under shaking, with different concentrations of W:E (100:0, 75:25, 50:50, 25:75, 0:100). At the end of the incubation, the samples were centrifuged for 5 min at 4000 rpm and subjected to multiple extraction process (n=3). Considering ex vivo digestion, after collecting gastric and intestinal fluids from swine (days 50-110, n=24 at slaughter house), they were pooled and kept at 4oC until use. Then, 500mg of hemp co-products were subjected to gastric digestion (39oC x 2h) in gastric fluid, and further exposed to intestinal fluid (39oC x 2h). Aliquots were taken at the beginning of gastric digestion (0h), at the end of gastric digestion (2h) and at the end of the intestinal phase (4h), to assess TPC and antioxidant activity during ex vivo digestion. Data are expressed as mean ± SEM. Considering green extraction, data obtained showed a valuable TPC content and antioxidant activity, in particular with 50:50 W:E extraction, even when compared to references co-products (e.g. grape marcs). Although the HP showed lower values than the other matrices, the HLs and HHs showed higher levels, with statistically significant differences for TPC (3551.12±98.54 and 1647.11±60.53 mg Tannic Acid Equivalent (TAE)/100g respectively) than grape marcs (1123.29±34.47 mg TAE/100g) (p<0.05). These values were also confirmed for ABTS. In particular, HLs showed statistically significant differences compared to HHs and grape marcs (2106,58±232,72 mg TE/100g and 1454,14±122,80 mg TE/100g respectively). Considering ex vivo digestion, HLs and HHs showed higher values than HP and grape marcs at each stage of the digestive process. These results encourage further investigations both to identify and characterise phenols and antioxidants responsible of such activities and to define the best level of inclusion of these matrices in feed to ensure high animal health and high production performance.