Distribution, antioxidant and characterisation of phenolic compounds in soybeans, flaxseed and olives
Distribution, antioxidant and characterisation of phenolic compounds in soybeans, flaxseed and olives
Year: 2013
Authors: Alu'datt, M.H. Rababah, T. Ereifej, K. Alli, I.
Publication Name: Food Chem.
Publication Details: Volume 139; Pages 93-99
Abstract:
The distribution of free and bound phenolic compounds present in soybean, flaxseed and olive were investigated. The phenolic compounds were fractionated on the basis on their solubility characteristics in water, alcohol, dilute base and dilute acid. Reversed phase high pressure liquid chromatography (RP HPLC) and mass spectrometry (MS) were used for identification of individual components of phenolic compounds. Antioxidant activity (AApercent) of free and bound phenolic compounds was measured using the linoleic acid/b-carotene assay. The water-soluble phenolic compound fractions represented 68 to 81percent, 50 to 72percent and 46 to 56percent of the total phenolic compounds measured in full-fat soybean, olive and flaxseed, respectively. Methanolic extraction of free phenolic compounds without heat, solubilised 21 to 56percent, 42 to 62percent and 34 to 51percent of the total phenolic compounds measured in soybean, olive and flaxseed, respectively; methanol extraction of free phenolic compounds with heat solubilised a further 24 to 34percent, 31 to 37percent and 36 to 37percent of phenolic compounds from soybean, olive and flaxseed, respectively. Further dilute alkali and dilute acid solubilised the remaining 10 to 40percent, 1 to 21percent and 12 to 29percent of the total phenolic compounds from soybean, olive and flaxseed, respectively. Results indicated that the full-fat meals of soybean, flaxseed and olive showed higher antioxidant activity compared to defatted meals. RP HPLC and LC MS/MS profil1 for soybean, flaxseed and olive indicate two classes of phenolic compounds designated as free and bound phenolic compounds. (Authors abstract)
Phenolic compounds are now recognised as important minor components of many edible plants, including many oil bearing plants such as soybean, canola, flaxseed and olive that are used as food or sources of food ingredients. Recently phenolic compounds of these oil bearing plants have been of reviewed interest due to their therapeutic properties such as anticancer, antiviral, antiinflammatory, hypolipidimic, and hypoglycemic. Flaxseed contains natural source of major plant food phytochemicals such as flavonoids, coumarins, lignans and phenolic acids. Several studies have reported that the presence of free phenolic compounds in oilseeds and their products may contribute to the dark colour, bitter taste and objectionable flavour of products. The roles of phenolic compounds as antioxidants to maintain the quality of food and to prevent or delay deterioration and maintain the nutritional value of food and food products, and to protect body tissues from oxidative damage have been described. Phenolic compounds have different mechanisms for their action as antioxidants; these include reduction of oxygen concentration, terminating of free radicals, decomposing primary products of oxidation to non radical species, preventing continued hydrogen abstraction from substrate and chelators of metal ions that are lead to the formation of peroxidation compounds.The overall objective of this study was to determine the contents of free and bound phenolic compounds in oil-bearing plants and to identify the major phenolic compounds and their antioxidant activity in soybean, flaxseed and olive using reversed phase high performance liquid chromatography (RPHPLC) and electrospray ionisation mass spectrometry (ESIMS).
Antioxidant activity of phenolic extracts show the antioxidant activity of free and bound phenolic compounds for full-fat and defatted flaxseed, soybean, olive meal based on methanol extraction, methanol extraction/heat, alkaline hydrolysis and acid hydrolysis carried out in sequence. The fullfat meals showed higher antioxidant activity as compared to defatted meals. Bound phenolic compounds that were extracted using alkaline hydrolysis showed higher antioxidant activity 68percent and 25percent from both full-fat and defatted soybean meals, respectively compared to free phenolic compounds. The free phenolic compounds extracted from full-fat flaxseed had higher antioxidant activity (58percent) compared to bound phenolic compounds extracted from full-fat flaxseed (7 to 21percent). The total free and total bound phenolic compounds for flaxseed meals were higher when compared to soybean meals. The results obtained from RPHPLC and LCMS profiles for soybean, flaxseed and olive meal indicated some differences in the phenolic compounds designated as free and bound phenolic compounds. RPHPLC showed that the flaxseed contains a number of both ‘free’ and ‘bound’ phenolic compounds while soybeans contain primarily ‘free’ phenolic compounds. The antioxidant activity of full-fat meals for both free and bound phenolic compounds in soybean and flaxseed had higher than defatted. Most of phenolic compound for full fat and defatted from flaxseed, soybean and olive exist in free form as compared to bound phenolic compounds. (Editors comments)
