Sorghum is unique among major cereals because some cultivars produce polymeric polyphenols
known as tannins (Butler 1990). All sorghums contain phenols and most contain flavonoids;
however, only cultivars with a pigmented testa, B1
_B2
_ genes, produce condensed tannins or proanthocyanidins.
Most cultivated sorghums do not contain condensed tannins even though nontannin,
phenolic compounds are occasionally reported as tannins. Sorghums are classified as type
I (without tannins), type II (tannins present in pigmented testa), or type III (tannins present in
pigmented testa and pericarp). Tannins have antioxidant properties and are currently being
considered as nutriceuticals (Hagerman et al. 1998).