GSPE is water-soluble polyphenolic extract from Vitis vinifera grape seeds. GSPE comprises catechin and epicatechins in monomeric (8%), dimeric (75%), and oligomeric (17%) forms. Examples of monomer, dimer, and oligomer structures are shown. The GSPE oligomer shown is composed of four monomer units: catechin, epicatechin, epigallocatechin, and epicatechin gallate. GSPE monomer, dimers, and oligomers likely are structurally heterogeneous.