New insight into erythema reduction induced by quercetin metal ions chelates

In dermatology, chelates play a significant role in skin care and treatment of skin diseases. Chelates involve coordination bonding between metal ions and organic molecules such as flavonoids. Quercetin (Q) is an extensively studied natural flavonoid with proven safety and anti-inflammatory properties. This study shows the role of two biocompatible metal ions, Iron (Fe2+) and Copper (Cu2+) in coordination bonding with Q in 2-Propanol 50% and 80% at 1:1 stoichiometry. Our results show that chelation involves the hydroxyl groups and occurs by coordination of Cu2+ to Q for the Ring A-B (Benzoyl group) resulting in a fluorescence emission peak at 530nm from the Ring B-C (Cinnamoyl group). This chelates Q+Cu2+ reduces mechanically induced erythema in the skin (Tanned type). A similar effect was observed in the chelate Q+Fe2+ where the coordination of Fe2+ to Q occurs for the cinnamoyl group resulting in an emission peak at 425nm from Benzoyl group of Q. The statistical analysis shows significant differences in the effects of Q+Cu2+ (p-value = 0.00001), Q+Fe2+ (p-value = 0.0003) respect to Q as well as between them (p-value =0.0029). Our results suggest that the interaction between Q and metal ions plays a central role in the inflammatory pathway. We conclude that the anti-inflammatory properties of Q were enhanced by both Q+Fe2+ and Q+Cu2+ chelates, highlighting the effect of Q+Fe2+ where the hydroxyl groups available in the cinnamoyl group of the Q molecule are the main intermediates to interact with Fe2+, which is a requirement to trigger the anti-inflammatory molecular events of Q molecules.