Catechins and Derived Procyanidins in Red and White Sorghum: Their Contributions to Antioxidant Activity

Flavan-3-ol monomers and derived procyanidins were determined by NP- and RP-HPLC-ESI(−)-MS/MS after extraction with a mixture of acetone/water/acetic acid (70:28:2, v/v). Logically, red sorghum was found to contain much higher amounts of monomers up to hexamers (S̀(P1–P6) = 61.4–450.2 mg/kg, (−)epicatechin equivalents) than white sorghum (0.2 mg/kg, (−)epicatechin equivalents). (+)Catechin was identified as its major monomer and B1 turned out to be the main dimer. Thiolysis confirmed that (+)catechin is the major terminal unit (50–88%), while (−)epicatechin is more frequent as extension units (50–86%). The contribution of monomers ((+)catechin and (−)epicatechin) and dimers (B1 and B2) to the total antioxidant activity determined by RP-HPLC-online TEAC was revealed to be very weak.