Protocatechuic aldehyde is a phenolic aldehyde, a compound released from cork stoppers into wine. This molecule can be used as a precursor in the vanillin synthesis by biotransformation by cell cultures of Capsicum frutescens, a type of Chili pepper. It is also found in the mushroom Phellinus linteus. Pharmacological effects Protocatechuic aldehyde regulates G protein-coupled estrogen receptor-1 (GPER-1) and exhibits protective effects in endothelial dysfunction and atherosclerosis. References See also Phenolic compounds in wine Hydroxybenzaldehydes