Post acid treatment on pressurized liquid extracts of sorghum bicolor grain and plant material improves quantification and identification of 3-deoxyanthocyanidins

Authors: SANTANA, ADINA - KANSAS STATE UNIVERSITY; Peterson, Jaymi; PERUMAL, RAMASAMY - KANSAS STATE UNIVERSITY; HU, CHANGLING - NORTH CAROLINA AGRICULTURAL AND TECHNICAL STATE UNIVERSITY; SANG, SHENGMIN - NORTH CAROLINA AGRICULTURAL AND TECHNICAL STATE UNIVERSITY; SILIVERU, KALIRAMESH - KANSAS STATE UNIVERSITY; Smolensky, Dmitriy

Submitted to: Processes
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/5/2023
Publication Date: 7/12/2023
Citation: Santana, A.L., Peterson, J.M., Perumal, R., Hu, C., Sang, S., Siliveru, K., Smolensky, D. 2023. Post acid treatment on pressurized liquid extracts of sorghum bicolor grain and plant material improves quantification and identification of 3-deoxyanthocyanidins. Processes. https://doi.org/10.3390/pr11072079.
DOI: https://doi.org/10.3390/pr11072079

Interpretive Summary: Both sorghum grain and sorghum plant material contain high amounts of antioxidants, also known as polyphenols. Extracting these compounds is important in order to utilize them in foods and other applications. Using acid during extraction has helped isolate these beneficial compounds. One drawback of using acid is that some techniques/machines do not allow for the use of acid. In this paper, we demonstrated that small scale acid treatment after high-throughput pressurized extraction is a useful tool in quantifying and purifying these compounds. These findings will allow scientists to use pressurized extraction on sorghum to make high amounts of extract while utilizing less acid, leading to less waste.

Technical Abstract: Sorghum is a unique food source for diverse phenolic compounds, including 3-deoxyanthocyanidins (3-DA). Acid-based extraction solvents are widely used to obtain phenolic compounds including unique 3-DA. Certain systems like pressurized extractions do not allow the use of strong acids during the extraction process, thus limiting the extraction, identification and quantification of 3-DA and other phenolics. This study evaluated post pressurized extraction acidification of sorghum phenolic extracts to increase identification and quantification of sorghum phenolics, namely 3-DA. Sorghum material included the bran (Sumac and PI570366 genotypes) and leaf and leaf sheath tissue (SC991 genotype). Acid hydrolysis of Pressurized Liquid Extraction (PLE) extracts was done with methanolic solutions incorporated with HCl (0, 0.5, 1, 2 and 4%, v/v). Phenolic compositions were investigated for total phenolic content and antioxidant. Quantitative and qualitative chromatographic methods including HPLC and TLC were used to determine overall phenolic profile and intensity of 3-deoxyanthocyanidins. Changes in color were determined using L*a*b* values. Color analysis showed that redness and color saturation increased after acidification. No statistical difference was found in total phenolic content of acidified extracts, except for SC991, which increased. There were no differences in antioxidant activity following acidification in all samples. Levels of 3-DA increased after acid treatment. Thin layer chromatography showed the qualitative predominance of luteolinidin in the extracts, which was corroborated via HPLC analysis. However, some flavonoid and phenolic acid concentrations were negatively affected by acid treatment, including taxifolin, quercetin, and chlorogenic acid. Overall, the phenolic profile improved after acidification, regarding 3-DAs and color. However, 0.5%v/v HCl methanol acidification of ASE extracts was sufficient in increasing 3-DA and color and there was no benefit of higher acid concentration.