Abstract
Recently there is a great interest in using high energy techniques (HET) which involve microwave or ultrasound-assisted extraction (MAE and UAE) for isolation of natural bioactive compounds from plant foods. Such bioactive compounds are phenolics which were determined from sunflower (Helianthus annuus L.) kernels and hulls (defatted) utilising two different high energy extraction techniques, ultrasound and microwave assisted solvent extraction. All samples were characterised by ultra-high-performance liquid chromatography-electrospray ionization-mass spectrometry (UHPLC-ESI-MS). The effect of parameters such as the nature of the solvent, volume of solvent, temperature and time is discussed. It is proved that the techniques applied had reduced solvent consumption and shorter extraction times, and extraction yields of the analytes were equal to or to some extent higher than those obtained with conventional techniques. Total Phenolic Composition (TPC) of samples examined was studied by the Folin-Ciocalteu method and results were presented in μg gallic acid equivalents (GAE)/g dry extract. Kernels proved to have the higher amount of TPC while the press residues had shown comparable TPC results. The antioxidant activity of samples was spectrophotometrically determined by 2,2-Diphenyl-1-Picrylhydrazyl (DPPH) assay using Butylated hydroxyl toluene (BHT) as reference compound to compare with samples. Sunflower seeds (kernels) showed again the highest antiradical efficiency (AE) compared to hulls and press-residue extract. Afterwards, ferric reducing ability of plasma (FRAP) and trolox equivalent antioxidant capacity (TEAC) assays were used for measuring the antioxidant capacity of samples. Press residue, a by-product of sunflower oil extraction, contained phenolics as shown by UHPLC-ESI-MS analysis. Hence, later on these compounds can be possibly utilised by food or neutraceutical industries. Phenolic substances characterised in hulls, kernels, and press residue were phenolic acids, mainly chlorogenic, caffeic, cinnamic, 4-hydroxybenzoic and p-coumaric.
Highlights
Plant derived foods have always been utilised for their potent therapeutic properties and have been in use for many years for the treatment of diseases by traditional practitioners
Four major variables: solvent polarity, solvent volume, temperature and extraction time were studied for their effects over antioxidant activity, Total Phenolic Composition (TPC) and phenolics composition from sunflower kernels, hulls and press residue extracts
The plant matrices analysed consisted of sunflower kernels from dehulled sunflower seeds and hulls, as well as press residue from whole seeds donated by an industrial biofuel production company
Summary
Plant derived foods have always been utilised for their potent therapeutic properties and have been in use for many years for the treatment of diseases by traditional practitioners. Sunflower seeds possess high nutritive value, being a good source of nutritional unsaturated fats, proteins, inorganic compounds, and phytochemicals. They have potent anti-inflammatory, anticancer, antioxidant, antihypertensive, analgesic, skin-protective, hypocholesterolemic, antibacterial activity and calming effects on nerves, muscles and blood vessels [5]. MAE and UAE are easy and rapid non-conventional extraction methods, applied to extract analytes out of solid matrices [8,9,10]. These two different extraction methodologies were compared both for total phenolic content and antiradical activity (AA). Four major variables: solvent polarity, solvent volume, temperature and extraction time were studied for their effects over antioxidant activity, TPC and phenolics composition from sunflower kernels, hulls and press residue extracts
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