3,4-dihydroxybenzoic acid is a kind of phenolic acid that is widely used in the medical field. It is commonly used in anti-cancer, antibacterial, anti-hyperglycemia, expectorant, antivenom and other drugs. It naturally exists in fruits, vegetables, nuts, tea, brown rice and some Chinese herbal medicines. It appears as a white to brown crystalline powder that changes color when exposed to air, breaks down and releases carbon dioxide in boiling water, and aqueous solutions of 3,4-dihydroxybenzoic acid turn green when encountered with ferric chloride and red when encountered with sodium bicarbonate.
3,4-dihydroxybenzoic acid is also important for our health, and can be obtained from foods containing anthocyanins, This is because 3,4-dihydroxybenzoic acid is the precursor of synthesis of complex molecules such as anthocyanins. It has a variety of biological activities and can play anti-inflammatory, antibacterial, antioxidant, anti-hyperglycemia, nerve protection and other functions.