Solvent effects on phenolic content, composition, and antioxidant activity of extracts from florets of sunflower (Helianthus annuus L.)

The common sunflower (Helianthus annuus L.) has been reported to be a rich source of phenolic compounds. The effects of solvent, of different polarities (distilled water (polarity P' = 10.20), 50%(v/v)aqueous methanol (P' = 8.40), 50% (v/v) aqueous ethanol (P' = 7.25), 90% (v/v) aqueous methanol (P' = 6.69), 90% (v/v) aqueous ethanol (P' = 4.89), and ethyl acetate (P' = 4.30), on the extraction of phenolics from ray florets and disc florets of H. annuus L were studied. Total phenolic contents, phenolic composition and antioxidant activity of the extracts were evaluated. Results indicated that the efficiency of solvents in the extraction of phenolics were in the following order: aqueous alcohols > water > ethyl acetate. The florets extracts with 90% (v/v) aqueous methanol presented the highest phenolic contents and the highest antioxidant activities. Nine and six phenolic compounds, respectively, were identified and quantified in aqueous alcohol extracts of ray florets and disc florets. p-Coumaric acid hexose and two caffeic acid hexose isomers were only detected in aqueous alcohol extracts of ray florets. The antioxidant activity correlated highly with total phenolic contents, indicating that phenolic compounds are the major contributors to the antioxidant properties of sunflower florets which could be considered as a good source of natural antioxidants. (C) 2015 Elsevier B.V. All rights reserved.