Oxalic Acid is a strong dicarboxylic acid occurring in many plants and vegetables and can be used as an analytical reagent and general reducing agent.
Oxalic Acid, a pathogenicity factor for sclerotinia sclerotiorum, suppresses the Oxidative burst of the host plant and directly inhibits the OGA-stimulated production of H2O2 by soybean cells, even in the absence of other fungal components[1].
[1]. Cessna SG, et al. Oxalic acid, a pathogenicity factor for Sclerotinia sclerotiorum, suppresses the oxidative burst of the host plant. Plant Cell. 2000 Nov;12(11):2191-200.