Abstract
Purpose : To employ response surface methodology (RSM) hinged on a central composite design (CCD) for the optimization of the extraction of polyphenols from Sorghum moench (Sorghum M). Methods : The combined influence of independent variables were assessed with RSM. Total phenolic content (TPC) determination was carried out using Folin-Ciocalteu method. Derivative compounds of phenolic acid were assayed using high performance liquid (HPLC). Antioxidant potential was determined through 1,1-diphenyl-2- picrylhydrazyl (DPPH) radical scavenging test. Results : The optimized extraction conditions were: 60.37 % ethanol, temperature of 59.07 o C and 2.97 h of extraction duration, which resulted in the extraction of maximum amount of TPC, i.e., 313 mg GAE/100g dry weight. The interactions between temperature and ethanol concentration, and between extraction time and ethanol concentration had significant effects of TPC (p < 0.05). Under these conditions, there was a consistency between the projected and actual experimental levels of polyphenols. A positive correlation was found between TPC and DPPH radical scavenging activity (r=0.67, p <0.05). Furthermore, ferulic acid correlated positively with p-coumaric acid (r = 0.54, p <0.01). Conclusion : These results underscore the usefulness of conditions for extraction in accurate quantification of antioxidants and phenolic compounds from Sorghum M, for possible application in large scale commercial extraction. Keywords : Response surface methodology, Sorghum moench, Polyphenols, Antioxidants
Highlights
Sorghum moench ranks next to wheat as one of the very important cereal grains worldwide [1]
Response surface methodology (RSM) is an excellent statistical approach for optimizing variables, and if properly used, it identifies optimal conditions for process improvement. It is useful for defining the influence of single or combined independent variables on the process, being that interactions cannot be determined by considering the various factors one-at-a-time. .The most frequently used form of RSM is central composite design (CCD) [6]
The Total phenolic content (TPC) and diphenyl-2- picrylhydrazyl (DPPH) radical scavenging potential were influenced by the type of solvent used, and by the conditions used for extraction
Summary
Sorghum moench ranks next to wheat as one of the very important cereal grains worldwide [1]. RSM is an excellent statistical approach for optimizing variables, and if properly used, it identifies optimal conditions for process improvement It is useful for defining the influence of single or combined independent variables on the process, being that interactions cannot be determined by considering the various factors one-at-a-time. The simulataneous influence of two process variables on TPC content of sorghum extracts was determined with an orthogonal rotatable CCD for K=3 factors in a quadratic function, with ethanol concentration and temperature as variables, while TPC and DPPH radical scavenging ability formed the responses (Table 1). Peak area at maximum absorption was employed in calculating the phenolic acid levels This was carried out according to a method described previouly [10].
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