A phage display system for the selection of peptides binding to heterologously expressed human melanocortin receptor 1 on the surface of insect cells has been established. It could be shown that phage particles displaying the natural ligand α-melanocyte-stimulating hormone bind selectively to cells expressing this receptor and that these phages exhibit biological activity on mouse B16F1 melanoma cells. Insect cells were superior to other cell lines tested and have been used to select binders from a small library, in which critical determinants (Phe⁷-Arg⁸-Trp⁹) were kept, whereas the flanking regions where allowed to variate freely. One peptide displaying little similarity with native hormone was found that binds to the receptor also in its free form with an affinity of 7 nm. It showed a remarkable selectivity for this receptor, because it binds to the other melanocortin receptor subtypes with a maximum affinity of 21 μm. This is the first time phage display has been used successfully with G-protein-coupled receptors lacking an extracellular binding domain.

BACKGROUND: Berry pomaces contain biologically active substances and therefore may have considerable potential applications in food and pharmaceutical industries. However, there is a lack of studies on extracting these valuable products from berry pomaces. OBJECTIVE: This study aims to evaluate major constituents of five Vaccinium spp. berry pomace extracts and investigate their antioxidant, hypoglycaemic and hepatoprotective properties. METHODS: Total anthocyanin, procyanidin and polyphenol contents in berry residues were measured by spectrophotometric pH-differential, 4-dimethylaminocinnamaldehyde and Folin–Ciocalteu method, respectively. Identification and quantification of separate compounds were assessed by ultra-performance liquid chromatography and liquid chromatography-time-of-flight-masspectroscopy. Anti-hyperglycaemic properties of pomace extracts were evaluated based on inhibition of α-amylase and α-glucosidase activity. Extract hepatoprotective effects were estimated based on increased human hepatic cell line HepG2 viability in oxidative stress conditions. RESULTS: The extracts possessed strong antioxidant effects and efficacy for inhibiting the activities of enzymes involved in carbohydrate digestion and for protecting hepatic cells from oxidative damage. CONCLUSIONS: Hepatoprotective and hypoglycaemic properties of berry pomace extracts may be due to the presence of active polyphenols and their synergistic effects. Our results support the use of berry pomaces for designing standardised formulations for the prevention of chronic diseases associated with oxidative stress.