Steviol glycosides are terpenoid compounds, composed of a tetracyclic diterpenoid (ent-kaurenoic) backbone, the so-called steviol, which forms O-glycosidic and ester bonds to different sugars.

The biosynthetic pathway of steviol glycosides has been elucidated in large parts up to now. Early steps of the synthesis involve the formation of the isoprenoid basic units via the deoxyxylulose phosphate (DXP) pathway,^3,4,12  a mevalonic acid independent pathway, which has been located in the plastids.^5,6 

It further shares four early steps of the biosynthesis of gibberellins (GA),⁷  which are known to be phytohormones with endogenous growth regulatory function.^8–10  The function of steviol glycosides themselves in the plant, however, is not yet clarified, although many suggestions had been made until now, including the gibberellin like or inhibiting activity of the aglycone steviol,^11–13  feeding deterrent activity,^14,15  function as osmolyte¹²  or oxidative stress inhibitory activity.^16,17