Characterization of Onosma bracteosum Hausskn. & Bornm. and Onosma thracicum Velen. Based on Fatty Acid Compositions and α-Tocopherol Contents of the Seed Oils

Year 2009, Volume: 68 Issue: 2, 75 - 83, 08.11.2010

Tamer Özcan

Abstract

Turkey is one of the important centres of origin for genus Onosma (Boraginaceae) with about 95 species including 48 endemics (ca.50%). A very limited number of investigations for fatty acid patterns and α-­tocopherol contents of the seed oils were reported in this genus. Some differences were observed in total oil (18.8-24.0%) and α-tocopherol contents (1.66-46.03%) between species. Major unsaturated fatty acids were α-linolenic (38.70-41.05%), linoleic (16.13-18.38%) and oleic acids (11.86-12.96%) respectively. Palmitic (6.32­7.71%), ɤ-linolenic (6.36-6.92%) and stearic (2.15-2.32%) acids showed considerable levels. Other fatty acid concentrations were at minor concentrations below 1 % of the seed oils. Total oil content in addition to oleic and α-linolenic acids quantified at higher levels in endemic O. bracteosum. The other fatty acids and α-tocopherol were observed at higher concentrations in O. thracicum. Some variations were examined in quantities, total percentages and the ratios of saturated and unsaturated fatty acids as additional chemotaxonomic markers. Differences for whole series of fatty acids were not significant between species but, significantly difference was found based on six calculated ratios of the fatty acids (p<0.05). Investigated Onosma species could be evaluated as the alternative wild sources for the production of essential fatty acids (EFA) including α-linolenic (ω-3), linoleic and unusual ɤ-linolenic (ω-6) acids.

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