Inhibition of Aromatase andα-Amylase by Flavonoids and Proanthocyanidins fromSorghum bicolorBran Extracts

Abstract

We compared the ability of simple flavonoids and proanthocyanidins in Sorghum bicolor bran extracts to inhibit enzymes in vitro. In particular, aromatase is a target for breast cancer therapy, and inhibition of α-amylase can reduce the glycemic effect of dietary starches. Proanthocyanidin-rich sumac sorghum bran extract inhibited α-amylase at a lower concentration (50% inhibitory concentration [IC₅₀]=1.4 μg/mL) than did proanthocyanidin-free black sorghum bran extract (IC₅₀=11.4 μg/mL). Sumac sorghum bran extract inhibited aromatase activity more strongly than black sorghum bran extract (IC₅₀=12.1 μg/mL vs. 18.8 μg/mL, respectively). Bovine serum albumin (BSA), which binds proanthocyanidins, reduced inhibition by sumac but not black sorghum bran extract. When separated on Sephadex LH-20, sumac sorghum proanthocyanidins inhibited both enzymes but showed reduced inhibition with BSA. Flavonoids from either cultivar had higher IC₅₀ values than proanthocyanidins, and BSA had little effect on their inhibition. Proanthocyanidins and simple flavonoids in LH-20 fractions both inhibited aromatase with mixed kinetics and affected K(m) and V(max). The results show that potential health benefits of sorghum bran may include actions of monomeric flavanoids as well as proanthocyanidins.

Sorghum condensed tannins encapsulated in kafirin microparticles as a nutraceutical for inhibition of amylases during digestion to attenuate hyperglycaemia

“…The SCT (100% methanol extract from sorghum) used in this study was a stronger α-glucosidase inhibitor than the sorghum phenolic extract of Kim et al (2011) (IC 50 = 0.4 µg/ml versus 1.1-1.4 µg/ml), using a similar inhibition assay. However, the sorghum phenolic extracts of Kim et al (2011) (lowest IC 50 = 2.9 µg/ml) and Hargrove et al (2011) (1.4 µg/ml) were apparently far stronger α-amylase inhibitors than the SCT used in this study (554.5 µg/ml). The α-amylase inhibitory data are, however, not directly comparable.…”

Total Phenolics, Antioxidant Activity and Anti-Diabetic Capacities of Selected Iraqi Medicinal Plants

“…Our results showed that the inhibitory activity of the tested plants against both α-glucosidase and pancreatic α-amylase was positively correlated with the total phenolic compounds contents. Similarly, some studies have shown that the inhibitory activities of plant-based extracts or products against α-glucosidase and pancreatic α-amylase can be linked to the total phenolic compounds and flavonoids contents [52,53]. These correlations may indicate the importance of phenolic compounds as mediators for the inhibitory effects of plant-based foods on α-amylase and α-glucosidase.…”

Sorghum: An Underutilized Cereal Whole Grain with the Potential to Assist in the Prevention of Chronic Disease

“…(12) The lower starch digestibility reported for sorghum foods is not an intrinsic property of the sorghum starch granules themselves, but appears mainly to be a consequence of the interactions of the starch with the endosperm protein matrix, as well as with cell wall material and polyphenolic compounds, such as condensed tannins and flavonoids. (37)(38)(39)(40)(41) These interactions inhibit carbohydrate-hydrolyzing enzymes, such as α-glucosidase and α-amylase, thereby lowering starch digestibility. (42) The presence of the protein matrix has also been associated with reduced starch gelatinization during cooking resulting in partially-gelatinized sorghum starch granules that may resist enzymatic degradation in vivo.…”