QS-7

**QS-7** is a natural saponin compound isolated from the bark of the Quillaja saponaria (QS) Molina tree, serving as a vaccine adjuvant with immunostimulating properties for anti-tumor and anti-infectious activities. It induces a balanced Th1/Th2 immune response, including strong CD8+ cytotoxic T lymphocyte (CTL) production, comparable to QS-21 but with reduced hemolytic and lethal toxicity due to its more hydrophilic structure featuring extra monosaccharide units in the C28 oligosaccharide domain and an acetyl group instead of a long chiral acyl chain at the fucosyl unit. QS-7 has molecular weight 1863.89 and formula C83H130O46, and synthetic analogs have been developed to tune its adjuvanticity, with one analog potentiating mixed Th1/Th2 responses effectively in preclinical immunization studies against antigens like rHagB and DnaK.[1][3][5]