Copper nanoparticles (Cu NPs) were synthesized via a green method by using of Plantago asiatica leaf extract as natural solvent and reaction biomedia under environmentally benign reaction conditions. It was observed that use of Plantago asiatica leaf extract makes a simple, eco-friendly and cost effective method for the preparation of the Cu NPs and can reduce copper ions into Cu(0) within 5 min of reaction time without using any stabilizer or surfactant agent. The progress of the reaction was monitored using UV-Visible spectroscopy. Polyphenolics could be adsorbed on the surface of Cu NPs, possibly by interaction through pi-electrons interaction in the absence of other strong ligating agents. The catalytic activity of the Cu NPs was evaluated by cyanation of aldehydes in the extract as a green solvent. This method provided several advantages such as cleaner easy work-up, shorter reaction time and higher yield. Cu NPs were characterized by FT-IR, UV-Vis, TEM, X-ray diffraction and the synthesized products were characterized by FT-IR and H-1 NMR. (C) 2017 Elsevier Inc. All rights reserved.