Agave marmorata Roezl is an endemic succulent specie from the Oaxaca-Puebla area of Mexico. This plant is a medicinal recourse and contain a rich variety of saponins-type compounds with multiples biological effects. Some of them have been shown to be anticancer, antibacterial, or having anti-inflammatory and immunoregulation effects. This paper is the first scientific report to describe the pharmacological activity and chemistry of the saponin smilagenin-3-O-[β-D-glucopyranosyl (1→2)-β-D-galactopyranoside] (1), isolated from Agave marmorata Roezl. Saponin (1) displayed immunomodulating activity when assayed on cultured macrophages. It inhibits NO production (EC50 = 5.6 mg/ml, Emax = 101%), as well as NF-κB expression (EC50 = 0.086 mg/ml, Emax = 90%). Using bioinformatic molecular docking, we identified a new smilagenin- PI3K kinase interaction site.