In addition to these elements, royal jelly contains what is probably the best known and most studied active ingredient: 10-hydroxy-2-decenoic acid (10-HDA). Royal jelly contains 2% of this fatty acid, described as having the property of slowing down the ageing of the body.
A mysterious component, this fatty acid has long been referred to as the "R-factor", for rejuvenation factor. Royal jelly also contains royalisin, a peptide that has an effect on Gram-positive bacteria. This peptide fraction is said to have an inhibiting effect on pathogenic germs (Bacillus larvae, Bacillus subtilis, Sarcina lutea), fungi and viruses.