Gold nanoparticles (AuNPs) were synthesized by the green method with activated Cochlospermum gossypium(carboxymethylated Cochlospermum gossypiumgum or carboxymethylated gum kondagogu: CMGK) as stabilizer and reducing agent. The obtained size of AuNPs was 11 ± 2 nm. The impacts of HAuCl4concentration, CMGK concentration, and reaction time on the synthesis of AuNPs were investigated. The techniques, UV − visible spectroscopy, FTIR, DLS, TEM, and powder XRD, were used for characterization. The reducing capacity of the synthesized CMGK-AuNPs was tested for reduction of 4-nitrophenol (4-NP) along with NaBH4. The effects of NaBH4, catalyst dose, and temperature were studied for reduction of 4-NP. The AuNPs showed good antibacterial activity against E. coliand Bacillus subtilis. The outcomes of the study indicated that CMGK–AuNPs have notable antimicrobial and environmental applications.