Using natural products is becoming ever more relevant, as innovative solutions are needed in the aim of healthier animals, better yields and environmental protection. The resistance of pathogens to traditional products, and the risk of residues to consumer’s health, are opening the door to ingredients of botanical origin as attractive substitutes to antibiotics and coccidiostats, among others.

Recently, research has put the focus in new and more sophisticated properties of secondary metabolites in living beings.

Quillaja saponins are structurally distinct from the ones derived from other plant species, which makes them display interesting properties regarding immune stimulation. For instance, quillaja saponins are excellent stimulators of antibody response to T-dependent protein antigens and T-independent antigens.

As well, the ability to move toward antigens and phagocytize them is thought to be an essential function of macrophages. Oral administration of quillaja saponins is very effective in inducing chemoattractant and ingestion activity of macrophages against typical pathogen antigen, as lipopolysaccharides.

When focusing in non-specific immunity, quillaja saponins elicit an innate immune response which is independent of any particular antigen, resulting in a potentiated immune system. In this sense, quillaja saponin has been reported to enhance the bacterial resistance in rainbow trout and shrimp (Litopenaeus vannamei).

Therefore, there is an increasing amount of information confirming that quillaja saponin has a protective effect against bacteria and stimulates the activation of immunity in finfish and shrimp. This suggests that receptors for this kind of saponin exist in macrophages and haemocytes of both fish and shrimp.