Orsellinic acid, more specifically o-orsellinic acid, is a phenolic acid. It is of importance in the biochemistry of lichens, from which it can be extracted. It is a common subunit of depsides.
It can be prepared by the oxidation of Orsellinaldehyde, or through a Michael adduct:
This can also be produced by the hydrolysis of either everninic acid or ramalic acid by boiling with barium hydroxide. When crystallized from acetone it forms crystalline needles with a melting point of 176 ðC. It also forms a crystalline hydrate with a melting point of 186-189 ðC when crystallized from water.
Orsellinic acid is biosynthesized by a polyketide pathway.