... is also a concentrated source of resveratrol (3,5,4¡Â-trihydroxy stilbene), an antioxidant phenol produced in response to fungi. Resveratrol has ... , citreorosein, questin, questinol, protocatechuic acid, (+) catechin, 2,5-dimethyl-7- hydroxychromone, 7-hydroxy-4-methoxy-5-methylcoumarin, flavonols, polysaccharides, and condensed tannins. Regulatory ...