Role of peptide primary sequence in polyphenol–protein recognition: An example with neurotensin

Polyphenols are known for their impact on health and one of their major properties is the formation of complexes with proteins. To investigate the involvement of polyphenol-protein complexes in health, the interactions between bioactive polyphenols and neurotensin were examined by structural NMR and molecular modeling. Neurotensin is a linear bioactive tridecapeptide and polyphenols seem to affect the NT metabolism. We studied the polyphenols resveratrol and its glucoside the piceid in order to observe the possible role of glucose group and the penta-O-galloyl-D-glucopyranose (PGG). NMR data and molecular modeling showed that interaction occurred with the three polyphenols involving hydrophobic stacking and hydrogen bonds. Moreover, the peptide primary sequence plays a role in the specificity of complex formation.

Differentiation of human melanoma cells induced by cyanidin-3-O-beta-glucopyranoside

Great attention has been recently given to a flavonoid of the anthocyanin class, cyanidin-3-O-beta-glucopyranoside (C-3-G), which is widely spread throughout the plant kingdom, and is present in both fruits and vegetables of human diets. In this study, we investigated the effect of C-3-G on proliferation and differentiation of human melanoma cells. Both morphological and functional parameters were evaluated, using electron and confocal microscopy, cytofluorometric analysis, HPLC assay, Western blot analysis, and enzymatic assay, as appropriate. A treatment with a single dose of C-3-G decreased cell proliferation without affecting cell viability and without inducing apoptosis or necrosis. The mitotic index and cell percentage in S phase were significantly lower in C-3-G treated cells compared with untreated control. C-3-G treatment induced, in a dose- and time-dependent manner, melanoma cell differentiation characterized by a strong increase in dendrite outgrowth accompanied with a remodeling of the microtubular network, a dramatic increase of focal adhesion and an increased expression of "brain specific" cytoskeletal components such as NF-160 and NF-200 neurofilament proteins. C-3-G treatment also induced increase of cAMP levels and up-regulation of tyrosinase expression and activity resulting in an enhanced melanin synthesis and melanosome maturation. Up-regulation of the melanoma differentiation antigen Melan-A/MART-1 in treated cells respect to the untreated control was also recorded. Data obtained provide evidence that a single treatment with C-3-G is able to revert the human melanoma cells from the proliferating to the differentiated state. We conclude that C-3-G is a very promising molecule to include in the strategies for treatment of melanoma; also because of its nutritional relevance.