By Szabolcs Szarka, Éva B. Héthelyi, Éva Lemberkovics, István Bálványos, Éva Szőke, Edit Farkas and Inna N. Kuzovkina
Abstract: Abstract: The occurrence of volatile compounds in flowers and roots of intact plants and in vitro hairy root cultures of Tagetes patula L. was investigated by GC and GC/MS. The flowers oil was dominated by mono- and sesquiterpenes. The main component was the sesquiterpene hydrocarbon β-caryophyllene (50.2%). However, the oils of normal roots and hairy root cultures were found to contain sulfur-containing thiophene structures. The following four compounds were identified: 5-(3-buten-1-ynyl)-2,2’-bithiophene (BBT), 5-(3-penten-1-ynyl)-2,2’-bithiophene (PBT), 2,2’:5’,2”-terthiophene (α-terthiophene) and 5-(4-acetoxy-1-butynyl)-2,2’-bithiophene (BBTOAc). The main components were BBT (47.0%) and α-terthiophene (19.8%) in the normal root oil and BBT (25.0%), α-terthiophene (14.3%) and BBTOAc (13.7%) in hairy root oil, respectively. Key Word Index: Tagetes patula, Asteraceae, essential oil composition, β-caryophyllene, palmitic acid, α-terthiophene, in vitro culture.
Introduction
Tagetes patula L. (Asteraceae), commonly known as French marigold, is native of Mexico and other warmer parts of America. The plant is named after Tages, the Etruscan God of prophecy. He supposedly emerged from the earth, predicted the future to the villagers who saw him and taught them the rites of prophecy then died. His words became the foundation of Etruscan prophecy.
Today, T. patula is a well-known ornamental plant widespread all over the world. The plant is a bushy annual and has yellow or orange flower heads. This herb biosynthesizes many biologically active products that can be used by the flavor, fragrance and pharmaceutical industries. The essential oil components have antibacterial and antifungal activity (1–8). Lutein dipalmitate, the main component of petal xanthophylls, is a pharmacologically active compound, and is used as ophtalmological agent. These compounds are used as food colorants as well, because of the greater solubility in vegetable oils compared to synthetic carotenoids (1). Tagetes species accumulate a wide range of thiophenes in their roots (2–5). Thiophenes exhibit strong biocidal activity thus environmentally safe, potential alternatives to synthetic pesticides (2). These compounds show impressive UVA-dependent biological activities. The mechanism of action is thought to be a type II mechanism which requires singlet oxygen exclusively. So, in the presence of UVA, the generated free radicals may induce fatty acid peroxidation and hence membrane damage. Thiophenes have extremely potent phototoxic effects on animal viruses with membranes, bacteria, fungi or nematodes (6–8).
In vitro plant cell cultures can be used to produce high value secondary metabolites. The transgenic hairy root culture is an excellent model system to study the secondary metabolism of biologically active compounds. These cultures are produced by Agrobacterium rhizogenes inoculation of intact plant seedlings. The rhizogenic bacteria strains contain a single copy of a large Ri plasmid. One part of this plasmid, called T-DNA, is transferred to wounded plant cells and it gets stably integrated into the host genome. After the transformation, profuse roots form at the inoculation site (2,4,5,9,10). These hairy roots produce growth hormones, so they grow very intensively on hormone-free media as well. These cultures have a better advantage over callus and dispersed cultures for their genetic and biochemical stability. In many instances, they can synthetize a range of secondary metabolites that are produced by intact plants (5).
The purpose of the present study was to investigate the volatile compound production and composition. Transformed hairy root cultures and different organs (flowers and roots) of intact T. patula were used for GC and GC/MS analyses.
