The grain’s biology explains much of its chemical wealth. A sorghum caryopsis consists of three layers: the pericarp or bran, the endosperm, and the germ, with the endosperm making up about 84 percent of the grain by weight. Crucially, the phenolic compounds are concentrated in the outer layers, precisely the fractions that milling often discards or diverts to animal feed. The color of the pericarp, which ranges from white and yellow to red, brown, purple, and black, offers a rough visual guide to phenolic density. Pigmented red, brown, and black varieties generally carry far richer phenolic profiles than white types, with black sorghums accumulating exceptionally high levels of 3-deoxyanthocyanidins when exposed to sunlight. But color is an imperfect predictor. The presence of condensed tannins depends on dominant B1 and B2 genes that control the development of a pigmented testa layer, meaning some red grains lack tannins entirely while genetics can outweigh appearance altogether.

Nutritionally, the review compiles striking differences among color variants. Carbohydrate content reaches up to 80 percent of the dry grain, with protein typically between 8 and 12 percent, though red and yellow types can exceed 23 percent. White sorghums tend to offer the most starch, with amylose levels reaching 40 percent, a feature that supports resistant starch formation and low glycemic responses. Pigmented types trade some starch energy for fiber, with black sorghum reaching crude fiber contents of nearly 9 percent, and they deliver substantially more iron, zinc, and magnesium than white counterparts. Potassium is the dominant mineral across all types, with black cultivars containing up to 3,566 milligrams per 100 grams, and the consistently high potassium-to-sodium ratio positions sorghum as a dietary strategy for managing hypertension. Like most cereals, sorghum is limited in lysine, but its fatty acid profile is dominated by heart-friendlier oleic and linoleic acids, which together with palmitic acid account for roughly 90 percent of the oil fraction.

The review’s most detailed analysis concerns the phenolic compounds themselves, mapping more than 110 distinct chemicals identified through advanced HPLC-DAD-ESI-QTOF-MS/MS profiling. Ferulic acid emerges as the undisputed leader, reported in every quantitative study examined and frequently accounting for more than 60 percent of total phenolic acids, mostly in bound form attached to cell wall polysaccharides. Gallic, chlorogenic, protocatechuic, caffeic, and p-coumaric acids round out the major phenolic acids. Among flavonoids, luteolin, apigenin, taxifolin, and naringenin appear most consistently, while the signature 3-deoxyanthocyanidins, luteolinidin and apigeninidin, define the pigmented cultivars. These rare pigments lack a hydroxyl group at the C-3 position of conventional anthocyanins, a small structural difference that confers remarkable stability against pH changes, heat, and bleaching agents such as ascorbic acid and sulfites. Total phenolic content varies more than tenfold between genotypes, from around 0.24 milligrams of gallic acid equivalents per gram in white grains to 11.5 in black cultivars, and antioxidant capacity measured by DPPH, ABTS, and FRAP assays tracks this variation closely.

The health implications documented across hundreds of studies are broad and mechanistically detailed. Sorghum phenolics neutralize reactive oxygen species directly while also upregulating the body’s own antioxidant defenses, increasing the activities of superoxide dismutase, catalase, and glutathione peroxidase in animal models. For metabolic disease, condensed tannins and flavonoids act as competitive inhibitors of alpha-glucosidase and alpha-amylase, in some cases exceeding the inhibitory potency of the antidiabetic drug acarbose, thereby slowing starch digestion and blunting postprandial glucose spikes. Compounds such as taxifolin activate AMPK and Akt signaling to boost glucose uptake in muscle cells, and sorghum extracts inhibit the formation of advanced glycation end products that drive diabetic complications. Anti-inflammatory effects operate largely through suppression of the NF-kappa B pathway, with molecular docking studies showing that apigeninidin and luteolinidin bind directly to critical cysteine residues in the NF-kappa B p65 subunit. Black sorghum extracts additionally protect vascular endothelium by downregulating NOX4 and upregulating nitric oxide synthase and heme oxygenase-1.

Perhaps most striking is the evidence that sorghum phenolics reshape the gut ecosystem. Because many phenolic acids are covalently bound to fiber, they survive upper digestion and reach the colon, where gut microbes release them and ferment them into short-chain fatty acids such as acetate, propionate, and butyrate. Diets rich in sorghum polyphenols increase beneficial genera including Akkermansia, Lactobacillus, Bifidobacterium, and Roseburia, while suppressing potentially harmful taxa such as Proteobacteria. The enrichment of Akkermansia is particularly noteworthy given its association with improved insulin sensitivity and metabolic health. Sorghum phenolics also strengthen the intestinal barrier by inducing tight junction proteins, raise villus height and goblet cell numbers in experimental models, and reduce colonic inflammation in chemically induced colitis. Early research even points toward neuroprotection, with sorghum extracts showing acetylcholinesterase inhibition and interference with amyloid-beta aggregation, though the authors caution that such findings remain confined to laboratory and preclinical settings.

The same chemistry that delivers benefits can also work against nutrition. Condensed tannins bind proline-rich kafirin storage proteins into complexes resistant to digestive enzymes, reducing protein digestibility, and catechol- and galloyl-containing tannins in brown sorghum form poorly absorbable complexes with iron in a dose-dependent manner. The review emphasizes that processing is the decisive lever for tipping this balance. Germination roughly doubles total phenolic content within 72 hours while cutting tannins by up to 38 percent and phytic acid by about 20 percent. Lactic acid fermentation releases bound phenolics through microbial esterases and glucosidases, raising antioxidant activity by up to 46 percent while degrading antinutrients. Extrusion cooking reduces tannins by 44 percent in red varieties even as total phenolics decline, and nixtamalization with lime slashes tannin content by as much as 82 percent. Remarkably, dry-heat treatments such as roasting and microwave heating often increase measurable phenolics and antioxidant activity, apparently by liberating bound compounds from the cell wall matrix.

Industrial applications are already emerging. White sorghum extract eliminated Campylobacter jejuni from inoculated chicken fillets within as little as six days while improving sensory scores, and tannin-rich sorghum combined with cowpea protein produces plant-based burgers with more protein, iron, and zinc and a firmer, meat-like bite. Greek yogurt fortified with 4 percent sorghum flour doubled its antioxidant capacity, and fermented sorghum beverages showed 57 percent inhibition of ACE-I, relevant to blood pressure control. Sorghum grain waste has been upcycled into biodegradable packaging films that extend the shelf life of fresh-cut apples by preventing browning and microbial growth. Meanwhile, the 3-deoxyanthocyanidins are positioning themselves as a natural colorant of unusual industrial value: their solutions retain 80 to 90 percent of their color after two hours at 95 degrees Celsius across the pH range of most foods, and they survive sterilization conditions that destroy ordinary anthocyanins.

The review’s authors, an Indonesian team led by Miftahurrahmi and colleagues working under the RIIM LPDP grant and the National Research and Innovation Agency, close with a research agenda that calls for randomized human clinical trials to validate the largely in vitro health evidence, standardized analytical protocols to make studies comparable, breeding programs that use genomic markers to stack beneficial phenolic traits, and scalable green extraction technologies such as ultrasound, microwave, and subcritical water methods that cut solvent use and processing time dramatically. They also highlight an underexplored frontier: phenolic-rich bran fractions that are currently diverted to animal feed could be valorized as functional food ingredients, a shift with particular relevance for Indonesia’s diverse sorghum cultivars and its push toward food diversification. As climate pressures intensify and consumers seek gluten-free, nutrient-dense alternatives, the humble grain once dismissed as birdseed may prove to be one of agriculture’s most quietly powerful assets.

Subject of Research: Phenolic compounds in sorghum grains, their chemistry, health effects, processing impacts, and applications in functional foods.

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

Article References: Miftahurrahmi, Antarlina, S. S., Ginting, E., Khamidah, A., Purwani, E. Y., Sihono, Ismail, N., Yustina, I., Ambarsari, I., & Fauziah, L. (2026). Sorghum phenolic compounds: Chemistry, health benefits, processing effects, and applications in functional foods. Journal of Agriculture and Food Research, 31, Article 103269. https://doi.org/10.1016/j.jafr.2026.103269

Image Credits: AI Generated

DOI: 10.1016/j.jafr.2026.103269

Keywords: sorghum, phenolic compounds, 3-deoxyanthocyanidins, condensed tannins, antioxidants, functional foods, gluten-free grains, food processing, fermentation, natural food colorants, gut microbiota, food security