A green synthetic approach to synthesize silver nanoparticles (AgNPs) using the stem extract of
Piper chaudocanum
for highly sensitive colorimetric detection of Hg
2+
with a low limit of detection of 23 nM and easy colorimetric read-out has been reported. In addition, the biosynthesized AgNPs demonstrated efficient antibacterial activity against
Escherichia coli
,
Pseudomonas aeruginosa
and
Staphylococcus aureus
. The morphology and structure of the as-synthesized AgNPs were examined using SEM, TEM, EDX, XRD and FT-IR analyses. The XRD and TEM results confirm the formation of AgNPs with an average particle size of 8–12 nm. The TLC, CC and HPLC revealed that four main compounds, pentacosanoic acid (
1
), piperine (
2
),
β
-sitosterol (
3
), and campesterol glucoside (
4
), isolated from
P. chaudocanum
extract act as reducing and stabilizing agents for AgNP formation, and piperine plays a vital role in green synthesis. The chemical structures of these compounds were determined by ESI MS, FTIR, and one- and two-dimensional NMR spectroscopic data analysis. This approach is an efficient, green, cost-effective, eco-friendly and promising technique for synthesizing AgNPs with applications in the colorimetric detection of Hg
2+
and antibacterial activity.