Rhizome and root yield of the cultivated Arnica montana L., chemical composition and histochemical localization of essential oil

Abstract

Arnica montana (L) is a medicinal plant whose flower heads are widely used for the topical treatment of bruises and sprains in phytopharmaceutical preparations. Despite being cultivated for flower heads production for a long time, the quantity and quality of its underground parts have not received much attention. In this study underground parts of a three-year cultivation trial have been estimated for yield potential and chemical composition of essential oil in two consecutive years. Yields of rhizome dry mass were about 208 kg ha(-1) and 647 kg ha(-1), and root dry mass were about 330 kg ha(-1) and 525 kg ha(-1) in the second and third year of growing period, respectively. The chemical composition of the essential oil from root and rhizome, obtained by hydrodistillation, was analyzed by gas chromatography-flame ionization detection and GC-mass spectrometry. At the end of second year essential oils from rhizome and root, yielded on average about 4.05% and 1.89%, and at the end of third year, they yielded 2.43% and 1.85%, respectively. The composition of essential oils was independent regarding cultivation trial factors with small differences regarding years. Aromatic hydrocarbons were predominant group of essential oil constituents (about 84% in average) and were identified as thymol derivates. Main individual components were 2,5-dimethoxy-p-cymene, thymol methyl ether and 2,6-diisopropylanisole. Furthermore, histochemical localization of essential oils in rhizome and root was carried out. Secretory structures responsible for essential oil synthesis and accumulation were studied using light, scanning and transmission microscopy. Secretory tissue is localized in the cortical region of the root and rhizome in form of idioblastic secretory cells and secretory cavities, respectively. Histochemical analyses confirmed the lipid nature of secreted material.