Abstract:
Phenolic compounds ubiquitously found in plants act as effective natural
antioxidants. Millets are underutilized cereals even in millet producing
countries but are good source of phenolics. In the present study, the effect of
extraction solvent and conditions on the total phenolic content (TPC), total
flavonoid content (TFC), and proanthocyanidins contents (PC), and
antioxidant activities of millet grains were investigated. Three solvent
systems, namely 70% acetone, 80% methanol, and 80% methanol with 1%
HCl were used. The extraction method used was refluxing at 600C, followed
by shaking in a water bath at 500C and room temperature. The TPC
measured using Folin Ciocalteu‟s reagent of finger and foxtail millets
differed from 34 to 111 and 4 to 14 µmol ferulic acid equivalents (FAE)/g
defatted meal, respectively. The TFC and PC contents of finger and foxtail
millets were in the range of 0.3–12.0 and 0.1–5.0 µmol of catechin
equivalents (CAE)/g of defatted meal, respectively. Aqueous methanol with
HCl was found to be the most effective solvent system among others used in
this study, and gave the highest TPC for finger and foxtail millet grains
under refluxing extraction. However, antioxidant activities, as determined by
reducing power (RP), trolox equivalent antioxidant capacity (TEAC) and
oxidation inhibition of β carotene in the β carotene-linoleate system differed
depending on the extraction techniques used. In conclusion, the results of
this study demonstrated that the solvent system as well as the extraction
method influenced the extraction efficacy of phenolic compounds in millet
grains and their antioxidant activities.
