Glucoside of o-coumaric acid (bound coumarin), which occurs as a precursor of coumarin e.g. in Galium odoratum(woodruff) or in sweet clover (Meliolotus officinalis). After enzymatic hydrolysis (e.g. during wilting), the genuinely present trans-cumaric acid is isomerised under UV light to cis-cumaric acid (coumarin acid), which is then transformed in cyclised form (lactonised) to coumarin. Only then does the aromatic smell typical of woodruff develop.