Anthocyanins are dietary bioactive compounds showing a range of beneficial effects against cardiovascular, neurological, and eye conditions. However, there is, as for other bioactive compounds in food, a high inter and intra-individual variation in the response to anthocyanin intake that in many cases leads to contradictory results in human trials. This variability could be caused at two levels, one at the bioavailability level and the other at the effect and mechanisms of action. In this context, we have thoroughly reviewed the scientific literature on anthocyanins variability caused by variation in bioavailability. Based on the literature reviewed, we have concluded that the variability in anthocyanins bioavailability might be produced by the lack of homogeneity introduced at three different levels: food matrix and food processing, enzymes involved in anthocyanin metabolism and transport, and anthocyanin metabolizing gut microbiota. However, it should be noted that the literature on anthocyanins bioavailability considering inter or intra-individual variability is still very scarce, which makes it difficult to reach any firm conclusion on the main metabolizing enzymes or bacteria that would be responsible for the variability in anthocyanin bioavailability.

The lipophilic character of quercetin suggests that it can cross enterocyte membranes via simple diffusion. Therefore, it should be more bioavailable than its glucosides, which require preliminary hydrolysis or active transport for absorption. However, the published human studies show that quercetin is less bioavailable than its glucosides. Assuming that low bioavailability of quercetin aglycone provided to humans as a pure substance is the result of its low solubility in the digestive tract, we studied its bioavailability from dietary sources in which quercetin was dispersed in the food matrix. In a randomized crossover study, 9 volunteers took a single dose of either shallot flesh (99.2% quercetin glucosides and 0.8% quercetin aglycone) or dry shallot skin (83.3% quercetin aglycone and 16.7% quercetin glucosides), providing 1.4 mg quercetin per kg of body weight. Blood samples were collected before and after consumption of shallot preparations. Plasma quercetin was measured on HPLC with electrochemical detection after plasma enzymatic treatment. The maximum plasma quercetin concentration of 1.02 ± 0.13 μmol/L was reached at 2.33 ± 0.50 h after shallot flesh consumption compared with 3.95 ± 0.62 μmol/L at 2.78 ± 0.15 h after dry skin consumption. The area under the concentration-time curve after dry skin consumption was 47.23 ± 7.53 μmol·h⁻¹·L⁻¹ and was significantly higher than that after shallot flesh intake (22.23 ± 2.32 μmol·h⁻¹·L⁻¹). When provided along with dietary sources, quercetin aglycone is more bioavailable than its glucosides in humans. Results point to the food matrix as a key factor.

Título en el postprint: Dual release of peptides and phenolics with antioxidant, ACE-inhibitory and antiinflammatory\ud activities from pinto bean (Phaseolus vulgaris L. var. pinto) proteins\ud by subtilisinsProduction of novel functional ingredients from legume proteins is a valuable strategy to boost their food use and intake. Aimed at a better exploitation of the functional properties of pinto bean hydrolysates, the effectiveness of two subtilisins (Alcalase and Savinase) for the simultaneous release of bioactive peptides and phenolics with antioxidant, angiotensin I converting enzyme (ACE) inhibitory and anti-inflammatory activities was investigated.\ud A higher proteolytic efficiency was observed for Alcalase that increased the concentration of small peptides in hydrolysates after 120 min. Savinase improved hydroxycinnamic acids and flavonoid contents in hydrolysates after 90 min due to its higher esterase activity. The\ud most active hydrolysates combined potent free radical scavenging (326¿348 mmol TE/g), ACE inhibitory (IC50 = 0.22¿0.26 mg/mL) and anti-inflammatory (28¿16% inhibition) activities. Peptide characterization of active hydrolysates confirmed the presence of bioactive fragments derived from phaseolin. These results evidence the promising potential of pinto bean hydrolysates as functional ingredients in the design of healthy foods.This research was cofunded by the Spanish Ministry of Economy and Competitiveness (MINECO) and the European Union through the projects AGL2010-16310 and AGL2013-43247-R and FEDER programme, respectively. P. Garcia-Mora thanks MINECO for providing a PhD fellowship. E. Peñas thanks the Spanish Ministry of Economy and Competitiveness, CSIC and European Social Fund for “Ramón y Cajal” contract.Peer Reviewe