Updated project metadata. 4-Hydroxybenzoic acid (4-HB) is the natural precursor for CoQ biosynthesis. Hydroxybenzoic acids derivatives (HBAs) have been recently used for the experimental treatment of primary CoQ deficiency. However, the mechanisms of these therapeutic effects remain obscure. In this study, we performed an analysis in plasma to evaluate the effect of supplementation with-resorcylic acid (-RA) or vanillic acid (VA), two HBAs potentially useful for the treatment of Coenzyme Q (CoQ) deficiencies, in an animal model of mitochondrial encephalopathy due to CoQ deficiency. The results help in the identification of potential biomarkers and/or endocrine factors that contribute to the pathophysiologic characteristics of the disease and its response to treatments, supporting important scientific and medical impacts for the use of -RA or VA in the treatment of CoQ deficiency.