A Comparative Study on Phenolic Content, Antioxidant Activity and Anti-Inflammatory Capacity of Aqueous and Ethanolic Extracts of Sorghum in Lipopolysaccharide-Induced RAW 264.7 Macrophages

Abstract

Sorghum is an important cereal with diverse phenolic compounds that have potential health promoting benefits. The current study comparatively characterized the phenolic contents of two novel black-seeded sorghum lines (SC84 and PI570481) using different extraction systems (water, ethanol and their acidified counterparts) and evaluated their 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 RAW 264.7 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 RAW 264.7 cells, sorghum extracts dose-dependently inhibited the 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.

Anti-Inflammatory and Antioxidant Properties of Plant Extracts

“…Similar results were obtained with different organ extracts of Abeliophyllum distichum by suppressing ROS production and/or inhibiting the activation of protein kinases (ERK1/2) when treating RAW264.7 cells with LPS [5]. Likewise, in LPS-activated RAW2647.7 cells, sorghum extracts inhibited the production of nitric oxide (NO), interleukin-6 (IL-6), and ROS, with ethanolic extracts showing greater anti-inflammatory activity related to tannin content [6]. Berries are a rich source of phytochemicals, especially phenolics, which are well known for their protective activity against many chronic diseases.…”

Phenolic Compounds in Whole Grain Sorghum and Their Health Benefits

“…Black sorghum bran phenolics extract (10% w/v in 50% ethanol) showed an inhibitory effect on TNF-α and IL-1β in lipopolysaccharide-stimulated peripheral blood mononuclear cells at dilutions of 1:100-1:200 and 1:100-1:400, respectively [38]. Hong et al [39] showed that acidified ethanol extracts of sorghum (SC84MX, SC84KS, PI570481) at 50 mg gallic acid equivalent/mL inhibited nitric oxide (NO) production up to 72.45%, 68.32%, and 95.36%, respectively. The increase in the secretion of TNF-α and IL-6 of RAW 264.7 macrophages infected by the bacteria Legionella pneumophila was observed after the treatment of polyphenol extracts of sorghum (PI570481) (0.625 and 1.25 mg/mL) [39].…”

“…Hong et al [39] showed that acidified ethanol extracts of sorghum (SC84MX, SC84KS, PI570481) at 50 mg gallic acid equivalent/mL inhibited nitric oxide (NO) production up to 72.45%, 68.32%, and 95.36%, respectively. The increase in the secretion of TNF-α and IL-6 of RAW 264.7 macrophages infected by the bacteria Legionella pneumophila was observed after the treatment of polyphenol extracts of sorghum (PI570481) (0.625 and 1.25 mg/mL) [39]. The mRNA expressions of IL-6 and IL-β of RAW 264.7 macrophage cells were significantly inhibited by the soluble phenolic extracts of the sorghum variety (Tong Za 117) at 300 to 500 mg/mL and 50 to 500 mg/mL, respectively, though a non-toxic mechanism [37].…”

Sorghum: Nutritional Factors, Bioactive Compounds, Pharmaceutical and Application in Food Systems: A Review

“…In the studied extracts, tannins were the most dominant polyphenols (11,11,136,11 mg of the epicatechin equivalent/g of sorghum). Sorghum extracts have been more powerful than NO radicals in DPPH scavenging activity [89]. In the meantime, the capacity to inhibit DPPH production seemed much greater as all sorghum extracts compared to a further study with an average of 90% of antioxidant activity against DPPH for three separate genotypes.…”