PHENOLIC ACIDS OF RHAPONTICUM CARTHAMOIDES

Abstract

The relation between the age of plants and the accumulation of phenolic acids, as well as their composition in particular organs of Rhaponticum carthamoides (Willd.) Iljin [Leuzea carthamoides D.C.] was investigated. The content of phenolic acids in rhizomes was higher than in roots (1.40% and 0.85% respectively). The content of these compounds in basal leaves was higher than in stem leaves. Underground organs and leaves were characterised by different compositions of phenolic acids. The dominant compound in the fraction of free phenolic acids from underground organs (rhizomes and roots) appeared to be gentisic acid and in the fractions of bound acids – o-hydroxyphenylacetic acid. The dominant compound in the fraction of free phenolic acids from basal leaves was protocatechuic acid. The biggest share in the fraction of free phenolic acids from stem leaves had ohydroxyphenylacetic and m-hydroxybenzoic acids. It is worth stressing that both gentisic acid (present in underground organs) and protocatechuic acid (in leaves) are known to reveal an immunotropic activity. INTRODUCTION Rhaponticum carthamoides (Willd.) Iljin [Leuzea carthamoides D.C.] – a perennial originating from Siberia – is considered to be one of the adaptogenic plants. Its rhizomes with roots have been used for many years as a stimulant, roborant and tonic agent. Recently, also Rhaponticum’s leaves have been taken into consideration as a medicinal raw material, especially in respect of their immunotropic properties. So far, it has been stated that immunomodulatory activity of Rhaponticum extracts could be connected with the presence of polysaccharides (Lamer-Zarawska et al., 1996). However, it is known that one of the important groups of plant constituents of immunotropic activity are phenolic compounds, including phenolic acids. They are responsible for many other pharmacological effects, too. Some of them reveal e.g. biligenic, antibacterial and antiviral activity (Borkowski, 1993; Borkowski and Milkowska, 1996). Phenolic acids have not been an object of thorough research in Rhaponticum as yet. The aim of the present study was to determine the content and composition of phenolic acids in underground and above ground organs of Rhaponticum, obtained from plants of different age. MATERIALS AND METHODS Plant Material Plant material for analysis was obtained from the experimental field of Dept. of Vegetable and Medicinal Plants. Rhizomes and roots of one-, twoand three-year-old plants were collected in October. Basal and stem leaves of two-, threeand four-year-old plants were harvested in May (at the stage of plant blooming). The raw materials were dried at 40°C. Quantitative Determination of Phenolic Acids The total polyphenolic acid content (converted into caffeic acid) was determined according to Polish Standard (PN-91/R-87019). Proc. Int. Conf. on MAP Eds. J. Bernath et al. Acta Hort. 597, ISHS 2003 120 Qualitative Determination of Phenolic Acids The isolation of phenolic acid fractions was made according to Krzaczek (1984). Free phenolic acids and those revealed after alkaline and acid hydrolysis were sililated (with BSTFA, Fluck) and identified by a GC method. Gas chromatography was performed on a Hewlett Packard 6890 as follows: capillary column HP-5, length 30 m, diameter 0.32 mm; detector FID temperature 250oC; injector temperature 220oC; carrier gas–helium with the flow rate 2 ml/min. Column temperature was programmed as follows: 60oC (2 min.), temperature increment 8oC/min. and finally 280oC (5 min.). Particular compounds were identified on the ground of retention times of the standard phenolic acids. RESULTS The content of phenolic acids in rhizomes was higher than in roots, regardless of the age of plants (Fig. 1). On the basis of GC, 17 phenolic acids were identified. They were present especially in a free form and some of them also in a bound form. The composition of these compounds in rhizomes and roots of oneand two-year-old plants was similar (in the fractions of free phenolic acids the dominant was gentisic acid and in the fractions of bound acids – o-hydroxyphenylacetic acid). Three-year-old plants were characterised by different composition of phenolic acids. There was no clearly dominant compound in the fractions of free phenolic acids, however in rhizomes a little bigger share in this fraction had protocatechuic acid and in roots p-hydroxybenzoic, protocatechuic and p-coumaric acids. In the fractions obtained after alkaline and acid hydrolysis of extracts, of both rhizomes and roots, the main compound was p-coumaric acid (Table 1). The content of phenolic acids in basal leaves of twoand three-year-old plants was higher than in stem leaves. In four-year-old plants there was no difference in the content of these compounds between basal and stem leaves (Fig. 2). The dominant compound in the fraction of free phenolic acids from basal leaves was protocatechuic acid. In the fractions of bounded acids the main compounds were proto