The Collaborative International Dictionary
Protocatechuic
Protocatechuic \Pro`to*cat`e*chu"ic\, a. (Chem.) Pertaining to, derived from, or designating, an organic acid which is obtained as a white crystalline substance from catechin, asafetida, oil of cloves, etc., and by distillation itself yields pyrocatechin.
Wiktionary
protocatechuic
a. (context organic compound English) Related to protocatechuic acid, protocatechuic aldehyde or their derivatives