Introduction sugar and lipids [3]. The main components of essential oil of Oregano plants are thymol, carvacrol,
1. Introduction sugar and lipids [3]. The main components of essential oil of Oregano plants are thymol, carvacrol,
Origanum vulgare L. is a member of the p-cymen and β-pinen [1, 4, 5]. Essential oil is a Lamiaceae family (Labiatea), commonly named mixture of volatile compounds produced in small oregano, wild marjoram, marzanjosh or mardaqoush, quantities as secondary metabolites from aromatic which grows abundantly on stony slopes and in and medicinal plants [6]. Thymol is a most valuable rocky mountain areas at a wide range of altitude [1]. crystalline phenol [7], have many biological The Origanum species, which are rich in essential activities, i.e. anti-oxidant [8], anti-cancer [9, 10], oils, have been used for thousands of years as spices anti-mutagenic [11], anti-inflammatory [12], and as local medicines. Arial parts of Origanum anti-microbial [13, 14], and anti-fungal activity [15]. vulgare are used in respiratory tract disorders such as The accumulation of secondary metabolites in plant cough or bronchial catarrh (as expectorant and tissue cultures has been obtained from various spasmolitic agents), in gastrointestinal disorders (as medicinal plants. The production of hyoscyamine and choleretic, digestive, eupeptic and spasmolitic agents) scopolamine has been reported in Callus cultures of as oral antiseptic, in urinary tract disorders (as Datura metel L. [16]. High in vitro production of diuretic and antiseptic) [2] and modulates blood indole alkaloids from Catharanthus roseus tissue
culture has also been reported [17]. In vitro studies in Corresponding author: Abedaljasim M. Jasim Al-Jibouri, Ph.D., assistant professor, research field: plant biotechnology.
Lamiaceae, callus culture of Origanum species were E-mail: [email protected].
Influence of Abiotic Elicitors on Accumulation of Thymol in Callus Cultures of Origanum vulgare L.
induced to study the effect of different type of nutrient
2.2 Callus Induction and Maintenance media and various growth regulators on different
Sterilized leaf segments (0.5 cm 2 ) were cultured on morphological responses [1], Arafeh et al. [6] studied solidified MS medium [20] supplemented separately the content of essential oil in intact plants (in vitro and with 0.5 mg/L or 1 mg/L 2,4-D, 0.5 mg/L or 1 mg/L ex vitro ), callus, and cell cultures in Origanum vulgare NAA, 0.5 mg/L 2,4-D and 3 mg/L BA and 0.5 mg/L and O. syriacum. The production of volatile oils 2,4-D and 3 mg/L Kn. All cultures were performed in has been shown in callus culture of Origanum the dark condition at 25 ± 2 °C. Data were recorded vulgare [18]. after 6 weeks on fresh and dry weight of callus. The The advantages of producing secondary compounds callus production was selected and maintained on using tissue culture technique are more reliable, fresh media (supplemented with 0.5 mg/L 2,4-D and 3 simpler, predictable, easy isolation and efficient mg/L BA which produced highest yield of callus) to compared with in vivo production. In addition, cell study the effect of abiotic elicitors on thymol culture can yield a source of defined standard
production.
phytochemicals in large volume and as technique could be a good model to evaluate various elicitors
2.3 Abiotic Elicitors Used
effects. Equal amount of callus (300 mg) was cultured on Secondary metabolite synthesis may be enhanced in maintenance medium (0.5 mg/L 2,4-D and 3 mg/L vitro by controlling the composition of the culture BA), three abiotic elicitors have been added to medium and the environment, certain secondary medium separately, 50 mg/L sucrose, 200 mg/L compounds are produced by the plant under the sodium chloride (NaCl) and amino acid proline at two influence of various biotic and abiotic factors that are concentrations 50 mg/L or 100 mg/L. All cultures known as “elicitors” [19]. were incubated under dark condition at 25 ± 2 °C. The main objective of present study was to examine Fresh and dry weights of callus were recorded after 6 the effect of exogenous elicitors on biomass weeks of incubation and thymol content were production and accumulation of thymol in callus
determined.
tissue of Origanum vulgare L. under dark condition.
2.4 Thymol Extraction