In this era, researchers have mainly concentrated on green synthesis of nanoparticles which is rapid, nontoxic, ecofriendly, reproducible and less cost when compared to the chemical and physical methods. Phytochemical reduction of AgNO3 to Ag NPs using root bark extracts of Catunaregum spinosa (C. spinosa) is reported in this manuscript. The resulting bio-reduced Silver nanoparticles (Ag NPs) were analyzed by UV–Visible Spectroscopy, FT-IR, XRD, TEM, Zeta potential and EDAX. Preparation of Ag NPs was identified by transformation of color from white to brown with maximum absorption at 442 nm due to Surface Plasmon Resonance. Crystalline studies by XRD inferred that the biosynthesized Ag NPs were crystalline in nature and further morphological studies revealed that the particles were spherically agglomerated with size ranging from 33 ± 2 nm. Moreover, the green synthesized Ag NPs were subjected for the degradation of toxic Amaranth dye using photoreactor exactly at 365 nm and pseudo first order kinetics were also stated the rate of degradation reaction were identified to be − K = 0.932 which provides significant results showing 94.07% degradation of azo grouped dye. © 2016 Elsevier B.V.