Also known as protocatechuic aldehyde, protocatechualdehyde is a naturally-occuring phenolic aldehyde that is found in barley, green cavendish bananas, grapevine leaves and root of the herb S. miltiorrhiza. Protocatechualdehyde possesses antiproliferative and pro-apoptotic properties against human breast cancer cells and colorectal cancer cells by reducing the expression of pro-oncogenes β-catenin and cyclin D1.