Document Type : Research Paper

Authors

• Fahimeh Gharaie ¹
• Monireh Cheniany ²
• Ali Ganjeali ¹

¹ Ferdowsi University of Mashhad

² Assistant Professor of Plant Physiology Department of Biology Faculty of Science Ferdowsi University of Mashhad-Iran

Abstract

Background and Objectives: Teucrium polium L. is a herbaceous plant from the mint family that has many uses in traditional medicine. In recent years, numerous medicinal effects such as anti-diabetes, anti-cancer, anti-spasm, and reducing fat and blood pressure have been reported. Therefore, cultivation of this plant under laboratory conditions is necessary to preserve its survival, reproduction, and increased secondary metabolites. Among the solutions, elicitors in the plant tissue culture technique are one of the most widely used methods to increase secondary-medicinal metabolites. Chitosan, as a biopolymer, induces defense responses, increases antioxidant enzyme activity, and accumulates phenolic compounds. In the present study, the effect of chitosan bio-elicitor was studied on some phenolic compounds of T. polium under in vitro culture to optimize secondary metabolites and increase antioxidant capacity.
Methodology: Leaf explants were prepared from preserved T. polium in hydroponic conditions and fed with Hoagland's solution. After sterilization with sodium hypochlorite 5% (v/v) and ethanol 70% (v/v), middle slices were prepared from the leaf explant and cultured on Murashige and Skoog (MS) culture medium containing separate and combined concentrations of benzyl amino purine (BAP)(1 and 1.5 mg.L^-1) and naphthalene acetic acid (NAA)(0.5 mg.L^-1). The samples were kept for four weeks in the dark at 25 degrees Celsius. With callogenesis, the samples were transferred to light conditions of 16 hours of light and 8 hours of darkness. At the end of the sixth week, the induced calli were subcultured. The calli were treated with chitosan at different concentrations (0, 50, 100, and 150 mg.L^-1). After eight weeks, green calli were collected. Finally, to prepare the final extract for biochemical assays, extraction was done from green calli. The content of phenolic compounds (phenol, flavonoid, flavone, and phenolic acids), antioxidant activity, and phenylalanine ammonialyase (PAL) activity was measured.
Results: According to the results, the application of different concentrations of chitosan (0, 50, 100, and 150 mg.L^-1) and all hormonal treatments (BAP1, BAP1.5, and BAP1.5+NAA 0.5 mg.L^-1) caused a significant increase in the content of phenolic compounds, antioxidant capacity, and PAL activity compared to the control samples. So the application of the simultaneous and combined treatment of BAP at a concentration of 1.5 mg.L^-1 with NAA at a concentration of 0.5 mg.L^-1, along with the treatment of 100 mg.L^-1 of chitosan induced green calli of T. polium in in vitro culture, results in the maximum content of phenolic derivatives (1884.95 for phenol, 936.65 for o-diphenol, 1462.28 for flavonoid, 631.07 for flavone, and 662.41 for phenolic acids). As compared to the control, the antioxidant capacities (measured by DPPH and FRAP assays) increased by 68.34 percent and 71.92 percent, respectively. A significant increase in PAL activity (65.81%) was observed in induced calli.
Conclusion: Considering the importance of T. polium as a medicinal plant, chitosan, a successful elicitor, promotes the synthesis of phenolic secondary metabolites. As a result, the increase of antioxidant power and PAL activity in the callus of T. polium.

Keywords

• Antioxidant
• Elicitor
• in vitro condition
• Callus
• Phenolic derivatives

Main Subjects

• Phytochemistry (extraction, identification and measurement of active components)