Sorghum phenolic compounds: Chemistry, health benefits, processing effects, and applications in functional foods

Sorghum ( Sorghum bicolor L.) is a drought tolerant cereal and the fifth most produced grain in the world with an annual production of over 60 million tons. The grains provide calories, protein, dietary fiber and minerals, especially iron and zinc, in amounts equivalent to rice or maize. Sorghum is rich in phenolic compounds, with more than 90% of these compounds concentrated in the pigmented outer layers of the grain (pericarp and testa). The main phenolics include phenolic acids (gallic and ferulic acids) and flavonoids (including flavones and flavanones) existing in all cultivars, whereas pigmented cultivars are characterized by the unique accumulation of 3-deoxyanthocyanidin. Condensed tannins, also known as proanthocyanidins, are also largely found in the pigmented testa. These bioactive compounds have been associated with numerous health-promoting effects, including antioxidant, anti-inflammatory, anticancer, and antidiabetic activities, which are mediated through free radical scavenging, modulation of enzyme activity, and regulation of the gut microbiota. However, high levels of tannins may exert antinutritional effects by binding to proteins and minerals, which reduces nutrient bioavailability. Processing greatly influences phenolic content, including germination, fermentation, and extraction. Advanced extraction techniques have been developed to maximize the recovery of sorghum phenolic compounds. Sorghum phenolic extracts are increasingly incorporated into functional foods and nutraceutical products, including antioxidant supplements and natural colorants. Future research should focus on enhancing the stability, bioavailability, and sensory characteristics, particularly reducing tannin-associated bitterness, while promoting the breeding of high-phenolic sorghum cultivars with desirable phenolic profiles to optimize their health benefit potential.