C18 Ganglioside GM3-d3 (d18:1/18:0-d3) is intended for use as an internal standard for the quantification of ganglioside GM3 by GC- or LC-MS. Ganglioside GM3 is a simple monosialoganglioside that demonstrates both antiproliferative and proapoptotic effects in tumor cells by modulating cell adhesion, proliferation, and differentiation. When used at a concentration of 20 μM, it suppresses angiogenesis and reduces endothelial cell proliferation and migration by inhibiting VEGFR2 and Akt phosphorylation. Furthermore, ganglioside GM3 has been shown to induce the dissociation of the insulin receptor-caveolin-1 complex from lipid microdomains, functioning as an inhibitor of insulin signaling and contributing to insulin resistance. This product is fully synthetic and has no variations in the fatty acyl chain or sphingoid backbone. It is intended for use as an analytical standard for the quantification of C18 Ganglioside GM3 by mass spectrometry.