Cost effective synthesis approach for green food packaging coating by gallic acid conjugated gold nanoparticles from Caesalpinia pulcherrima extract

Reactive oxygen species (ROS) are the most threatening element for shelf life of packaged food. Mainly increase ROS is related to enzymatic, photochemical and pathogen action in the packaged food. In this study the cascade in ROS is observed in the presence of gold nanoparticles (AuNPs) conjugated with gallic acid. This is an efficient and promising approach for decreasing oxidative damage and physiological deterioration of packaged food. Firstly, the amine stabilized AuNPs were synthesized to meet the demand of high stability and long shelf-life. The surface functionalization of gold nanoparticles with gallic acid from extract of Caesalpinia pulcherrima to get gallic acid conjugated AuNPs (GA-AuNPs) reduces the toxicity of chemically stabilized AuNPs. Characterization techniques like dynamic light scattering, SEM, UV-vis spectroscopy evaluated morphology and electrochemical technique such as cyclic voltammetry (CV) estimated free radical scavenging by GA-AuNPs. The antimicrobial and antioxidant properties for GA-AuNPs were also investigated for pure gallic acid (GA) and its derivatives. The excellency of GA-AuNPs for free radical scavenging was proved by remarkable shift in peak potential and decrease in peak current with high binding constant (K-b) value of 1.99 M-1. Moreover, a lower IC50 value 4 x 10(-9) g/mL synergistically contributes to higher antioxidant coefficient (K-a) against superoxide radical (O-2(center dot-)). The potential free radical scavenging ability and green catalytic action against microbes attributes GA-AuNPs the most suitable food packaging lining in food industry without any side effect.