Menthyl Lactate is an ester of menthol and lactic acid. Lactic acid is an alpha hydroxy acid; naturally produced in the process of bacterial fermentation, for example milk fermentation. Lactic acid is frequently used as an exfoliant and in anti-wrinkle products. C3H6O3 or C3H6O3/ CH3CHOHCOOH or HC3H5O3. https://pubchem.ncbi.nlm.nih.gov/compound/lactic_acid