A comparative study on phenolic contents, antioxidant activity and anti-inflammatory capacity in lipopolysaccharide-induced RAW 264.7 macrophages of sorghum aqueous and ethanolic extracts

Authors: HONG, SHAN - University Of Tennessee; PANGLOLI, PHILIPUS - University Of Tennessee; PERUMAL, RAMASAMY - University Of Kansas; Cox, Sarah; Noronha, Leela; DIA, VERMONT - University Of Tennessee; Smolensky, Dmitriy

Submitted to: Antioxidants
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/15/2020
Publication Date: 12/18/2020
Citation: Hong, S., Pangloli, P., Perumal, R., Cox, S.R., Noronha, L.E., Dia, V.P., Smolensky, D. 2020. A comparative study on phenolic contents, antioxidant activity and anti-inflammatory capacity in lipopolysaccharide-induced RAW 264.7 macrophages of sorghum aqueous and ethanolic extracts. Antioxidants. https://doi.org/10.3390/antiox9121297.
DOI: https://doi.org/10.3390/antiox9121297

Interpretive Summary: In this study, we compared three sorghum samples for their phenolic composition and their antioxidant activity, as well as effects in macrophage cells. The samples were high phenolic sorghum, PI570481, grown in Mexico, SC84 grown in Kansas, US and SC84 grown in Mexico. Using various methods of measuring antioxidants, the antioxidant capacity was quantified for the samples extracted with both ethanol based and water based solvents. Specific compounds were identified using high pressure liquid chromatography. Tissue culture studies using macrophages indicated that the sorghum samples exhibited anti-inflammatory activity. One major finding of this study is that there were no major differences observed between SC84 sorghum grown in Kansas and Mexico, making SC84 a viable genotype for breeding programs in order to grow high phenolic grain in the United States.

Technical Abstract: Sorghum is an important cereal with diverse phenolic compounds that have potential health promoting benefits. The current study comparatively characterized sorghum phenolic contents of two novel black-seeded sorghum lines (SC84 and PI570481) using different extraction systems (water, ethanol and their acidified counterparts) and evaluated antioxidant and anti-inflammatory activities. Phenolic compositions were determined by spectrophotometric assays and HPLC analysis. Antioxidant activities were assessed by radical scavenging effects on nitric oxide (NO) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radicals, and the oxygen radical absorbance capacity (ORAC). Anti-inflammatory capacity was estimated by measuring levels of pro-inflammatory markers produced by lipopolysaccharide (LPS)-induced RAW264.7 macrophages. Results showed that effects of solvent types and HCl on extraction efficiency differed among phenolic compounds and sorghum samples. Tannins were the most dominant polyphenols in the studied extracts (11.11-136.11 mg epicatechin equivalent/g sorghum). Sorghum extracts exerted more potent scavenging activity on DPPH than NO radicals. In LPS-activated RAW264.7 cells, sorghum extracts dose-dependently inhibited production of NO, interleukin-6 (IL-6), and intracellular reactive oxygen species (ROS), with ethanolic extracts showing greater anti-inflammatory activity. Positive correlations were noted between tannin content and DPPH radical scavenging activity, and anti-inflammatory capacity. These results suggest the potential role of tannin-rich sorghum extracts against inflammation and associated diseases.