Optimal extraction method and immunological effects of sorghum polyphenols

Abstract

Sorghum is a cereal grain with immense nutraceutical polyphenolic compounds that have demonstrated multiple beneficial qualities such as anti-proliferative, anti-cancer, anti-diabetic, anti-obesity, anti-inflammatory, and apoptotic effects. While there is a large amount of diversity within sorghum varieties in both quantity and composition of polyphenols, it is often found to possess high levels of tannins that may interfere with polyphenol extraction and detection. Here, the extraction process was evaluated, and multiple steps varied to determine the optimal procedure and solvent to be used. A combination of 70% ethanol and 5% citric acid solvent was found to be optimal, as it extracted some of the highest levels of polyphenols while minimizing effects on the bioactivity of the polyphenols on Human colorectal adenocarcinoma HCT15 and human hepatocellular carcinoma HEP2 cells. The extracts were then used to treat RAW 264.7 cells to evaluate their immunological effects. Both the HP (High Polyphenol; accession number, PI570481) and SC84 (high polyphenol brown sorghum) extracts demonstrated significant changes in cytokine production and DNA expression. The HP extract was also found to increase autophagy. In chapter 1, the nutritional and nutraceutical properties of sorghum polyphenols are explored. The different varieties and their basic structures are discussed, and the potential health qualities such as anti-cancer and anti-inflammation effects are evaluated. In chapter 2, the process of extracting total polyphenols from sorghum bran is evaluated and optimized. The effects of sorghum polyphenols on inflammation and the immune system are evaluated in Chapter 3 using LPS and IFN Y activated RAW 264.7 cells. RAW 264.7 cells showed significant increase in interleukin 6 (IL-6) and interleukin 10 (IL-10) when exposed to polyphenolic extracts from both sorghum lines. The RAW 264.7 cells also demonstrated structural changes by developing multiple large vacuoles over time. Finally, both sorghum varieties increased LC3 II production in the RAW 264.7 cells, indicating an increase in autophagy. These results indicate that sorghum polyphenols modulate the immune system and inflammatory response. They also provide support that sorghum polyphenols have anti-proliferative effects, and the optimization of food grade total polyphenolic extraction assay will be beneficial for quantification of total polyphenolic content in future research as well as dietary supplement development.