Mandelic acid (Standard) is the standard substance of Mandelic acid, and it is applicable for quantitative analysis, quality control, and related research in biochemical experiments. It is an isomer of cresotinic acid (2-hydroxy-3-methylbenzoic acid) and oxymethylbenzoic acid (2-methoxybenzoic acid). Derivatives of mandelic acid are formed as a result of metabolism of adrenaline and noradrenaline by monoamine oxidase and catechol-o-methyl transferase. It is also present in certain skin care products, is an intermediate molecule in the production of other biochemicals, may be used as an analytical reagent and is a precursor in the manufacture of dyes. Mandelic acid (acidomandelico) is found to be associated with phenylketonuria, which is an inborn error of metabolism.