Phyto-fabrication of metal nanoparticles is grounded on the use of synergistic redox potential of plant secondary metabolites altering metal valance states. The resulting nano state occupies incredible changed optical properties with improved activities. During plant-mediated fabrication, medicinally important bioactive secondary metabolite also form capping on freshly generated metal nanoparticles and becomes a source for additional enhancement of bio-efficacy. The capping effect of therapeutically significant secondary metabolites of the plants on the freshly produced metal nanoparticles is one of the governing factors of green nanotechnological enhancement in pharmacological activities. So far, any proof based on analytical evidences of capping effect has not been reported. The present short communication warrants confirmatory HPTLC fingerprinting evidence of capping effect of extracted saponin from the seed of the plant Madhuca longifolia on the freshly phytofabricated mono (Au, Ag) and bimetallic (Au-Ag) nanoparticles.