Bio-inspired synthesis of copper nanocatalysts using chlorogenic acid isolated from Prangos serpentinica for efficient aqueous-phase Henry reactions

In this study, chlorogenic acid (CGA) was isolated from the methanolic extract of Prangos serpentinica, a plant adapted to serpentine soils known for their unique phytochemical profiles. Using preparative HPLC, 9.85 µg of CGA was obtained per milligram of extract. The isolated CGA was then utilized to synthesize a bio-inspired copper(0) nanocomposite (CGA-Cu(0)) through complexation with Cu(II) ions followed by chemical reduction using sodium borohydride. The resulting nanostructures were characterized by FT-IR, XRD, EDX, SEM, and TEM analyses, confirming the formation of metallic copper nanoparticles within the CGA matrix, with sizes ranging from 20 to 50 nm. The CGA-Cu(0) nanocomposite was then evaluated as a heterogeneous catalyst in the Henry reaction under aqueous conditions. Systematic optimization revealed that 3 mol% of the catalyst in water at 70 °C provided β-nitroalcohols in high yields. Control experiments indicated the superior catalytic performance of CGA-Cu(0) compared to its unreduced form and bulk copper. The developed system presents an eco-friendly, cost-effective, and plant-based alternative to conventional metal catalysts in C-C bond-forming reactions. This study reports the first usage of CGA-metal complex as a catalyst in organic reactions.