Дослідження жирнокислотного складу деяких рослин родини айстрові (Аsteraceae)

Abstract

Introduction. Recently, much attention has been paid to the study of medicinal plants’ lipophilic complexes, part of which is fatty acids, which play an important role in the life activities of a human body. The plants of the Asteraceae family — yacon (the Smallanhus sonchifolius (Poepp. and Endl.) H. Robinson), stevia rebaudiana (Bertoni) Hemsley and cat’s paw (Antennaria dioica (L.) Gaertn.) contain the complex of biologically active substances, among which a significant place is given to lipophilic components (fatty acids, carotenoids, chlorophylls, etc.). In the sources of scientific literature, there is not enough information about the studied species’ fatty acid composition. Therefore, the purpose of our research is to study the lipophilic fractions of stevia leaves, yacon root tubers and leaves, cat’s paw herbs, and to determine the content of fatty acids in their composition.Research Methods. Lipophilic fractions of the studied species are obtained by exhaustive extraction of raw materials with chloroform in the Soxhlet apparatus. Determination of qualitative composition and quantitative content of fatty acids in the investigated medicinal plant material is carried out by the gas-liquid chromatographic/mass spectrometric method of fatty acids methyl esters on the gas chromatographic/mass spectrometric system Agilent 6890N/5973inert (Agilent Technologies, USA). The identification of fatty acid methyl esters in the test mixture is carried out by comparing the retention time of fatty acids methyl esters standard mixture (Supelco, USA). The NIST 02 mass spectrum library is used.Results and Discussion. The isolated lipophilic fraction from yacon root tubers – a thick oily homogeneous mass of brown colour with a pleasant specific odor; not soluble in water and ethanol, is readily soluble in chloroform. Lipophilic fractions of stevia leaves are of dark green colour; cat’s paw herbs – light green colour; according to other physical indicators, the obtained substances do not differ. It is established that the yield of lipophilic substances from yacon and stevia leaves are almost the same – (9.55±0.09)% and (9.05±0.07) %, from yacon roots – in 2.4 and 2.2 times smaller than leaves, respectively. The yield of the lipophilic fraction from cat’s paw herbs is (8.25 ± 0.09) %.9 fatty acids are detected in the lipophilic extract of yacon leaves and cat’s paw herbs, 2 of which are polyunsaturated (linoleic and linolenic). 8 fatty acids are detected in the lipophilic extract of stevia leaves, where linolenic acid is present in the largest number. The lipophilic extract of stevia leaves and cat’s paw herbs contains the saturated palmitic acid. The content of unsaturated fatty acids in the studied lipophilic extracts predominates over saturated. Their ratio in yacon leaves is 55.35:8.63; stevia leaves – 3.04:1.87; cat’s paw herbs – 29.09:20.26, respectively. Only the linoleic and linolenic acids are identified in the lipophilic extract of yacon root tubers.Conclusions. 1. The fatty acid composition of the lipophilic fractions of stevia leaves, yacon root tubers and leaves, and cat’s paw herbs is determined by the gas-liquid chromatographic/mass spectrometric method for the first time.2. The content of unsaturated fatty acids in stevia and yacon leaves, and cat’s paw herbs predominates over saturated. Polyunsaturated fatty acids (linoleic and linolenic) are dominant in the investigated objects.3. Only the linoleic and linolenic acids are identified in yacon root tubers.