Analytical characterization of lipids and antioxidant components in Flaxseeds (Linum usitatissimum)

Abstract

Flaxseed or linseed (Linum usitatissimum) belonging to family lineaceae is an ancient crop and has been grown for its fiber (linen) and oil seeds since 9000 to 8000 B.C. Flaxseed is cultivated in almost fifty countries of the world including Pakistan. Flaxseed is a rich source of alpha linolenic acid, very efficient antioxidant system and dietary fiber. These characteristics and the health benefits associated with these characteristics of flaxseed have made it a great attraction for the researchers in the field of functional foods and neutraceuticals. Keeping in view the immense importance of flaxseed as neutraceutical and functional food, the present study was planned to assess the nutritional composition, oil characteristics and antioxidant potential of different flaxseeds cultivars grown in Pakistan. Moreover qualitative and quantitative analysis of the flaxseed phenolics was done by HPLC and LC-MS. The proximate analysis of flaxseed that the oil, moisture, crude protein, fiber and ash contents in the seeds of different cultivars of flaxseed were observed to range from 33.25 to 38.38%, 5.98 to 6.22%, 16.02 to 18.50%, 23.30 to 26.80% and 3.21 to 3.60% respectively. Gamma tocopherol was observed to be the major tocopherol present in the oil with minor contents of alpha tocopherol. The unsaturated fatty acids in the oils extracted from different cultivars were observed to be in the range of 88.79 to 89.78%, with alpha linolenic acid with the highest contents and ranged from 44.51 to 54.87%. From the data for the physicochemical characteristics of the oils it was observed the oils were up to the mark in quality as compared to the international standards. 80% aqueous ethanol and methanol were the most effective solvents for recovering antioxidant components from flaxseed while the pure ethanol and acetone had shown the least efficacy towards isolation of flaxseed antioxidants as established by the antioxidant activity analysis by different methods. Furthermore, the sonication assisted shaking proved to be superior in extraction of antioxidant components. HPLC and LC-MS analysis established that SECO (secoisolariciricinol) was the major phenolic (lignan) and dominated all the other phenolic compounds. SDG, ferulic acid, coumaric acid, chlorogenic acid and gallic acids were the other phenolic compounds detected in the flaxseed. The data presented would certainly help to ascertain the potency of the flaxseeds grown in Pakistan, as viable source of natural antioxidants and alpha linolenic acid, thus suggest their uses for nutraceutical and functional food applications.