ortho-Hydroxyphenylacetic acid (2-hydroxybenzeneacetic acid) can be found in a number of food items such as natal plum lemon verbena half-highbush blueberry and parsley which makes ortho-hydroxyphenylacetic acid a potential biomarker for the consumption of these food products. ortho-Hydroxyphenylacetic acid can be found primarily in blood feces and urine.

Lawsone (2-hydroxy-1,4-naphthoquinone), also known as hennotannic acid, is a red-orange dye present in the leaves of the henna plant (Lawsonia inermis) as well as in the flower of water hyacinth (Eichhornia crassipes).

MPO-IN-28 is a novel potent irreversible Myeloperoxidase (MPO) inhibitor with IC50 of 44 nM.