Effect of Ultrasonication on the Physicochemical Properties of Sorghum Kafirin and Evaluation of its Anti-inflammatory Properties <i>In Vitro</i>

Sorghum is one of the hardiest, most drought resistent cereal grains known to exist, providing the bulk of nutritional content for many semi-arid regions and developing countries throughout Africa and southwestern Asia. It contains dense nutritional value, but due to inhibition factors within the grain, much of these nutrients are indigestible. Access to these nutrients, which have shown to contain high contents of bioactive molecules linked to the decrease of prevalence of chronic disease, must then be facilitated before consumption. In sorghum, these molecules could include complex carbohydrates, proteins and polyphenols. The overall objective of this study was to determine the effect of ultrasonication on kafirin’s physicochemical properties and evaluate its effects on inflammatory response in vitro. Ultrasonication is a processing tool causing self-collapsing micro-cavitations disrupting structure and altering function. Kafirin was extracted and purified from sorghum flour using differential solubility extraction methods, concentrated and lyophilized. The effects of ultrasonication on the secondary structure of kafirin and its stability after ultrasonication against pepsinpancreatin hydrolysis were measured. Ultrasonication altered the secondary structure of kafirin, increased its solubility and improved its antioxidant capacity. Kafirin was also evaluated for its ability to halt the production of pro-inflammatory cytokines through inhibition of reactive oxygen species production in THP-1 human macrophages primed with lipopolysaccharides (LPS). An association exists between overexpressed inflammatory response from aberrant activation of the inflammatory pathway and chronic diseases. LPS-treated THP-1 macrophages were treated with 50 and 100 μg (microgram) kafirin/mL. The treatment of kafirin led to inhibition of the production of intracellular reactive oxygen species (ROS), disrupting the inflammatory signaling cascade and reducing the production of pro-inflammatory cytokines IL-6, IL-1β, and TNF-α. These results showed that kafirin can inactivate the inflammatory response pathway by inhibiting intracellular ROS production. This study is the first to report on ultrasonication as a viable option for increasing the digestibility of kafirin as well as kafirin’s potential as chemopreventive agent against chronic disease associated with aberrant inflammation.