Lignan accumulation in callus and Agrobacterium rhizogenes-mediated hairy root cultures of flax (Linum usitatissimum)

Agrobacterium rhizogenes is gaining intensity in research to develop and produce a large number of commercially important secondary metabolites, such as lignans. Worldwide, lignans are receiving great attention because of their putative beneficial effects on human health. In this study, we investigated the potential of callus and A. rhizogenes, hairy roots, of flax Linum usitatissimum in accumulating lignans, namely, secoisolariciresinol diglucoside (SDG), secoisolariciresinol (SECO) and matairesinol (MAT). Callus cultures were established on Gamborg B5 medium supplemented with 2,4-dichlorophenoxyacetic acid (2,4-D) alone or in combination with 6-benzyladenine or gibberellic acid (GA3). These callus cultures were transformed with A. rhizogenes, which were initiated on 1.0 mg l(-1) 2,4-D + 0.5 mg l(-1) GA3 or 1.0 mg l(-1) GA3 media. Both hairy root culture 1 and hairy root culture 2 accumulated SDG, SECO and MAT with a total lignan concentration of 1.227 and 1.057 A mu mol g(-1), respectively. However, non-transformed cultures did not accumulate MAT but accumulated SECO. Determination of total phenolic content by high-performance liquid chromatography revealed higher phenolic acid content in hairy root cultures compared with that in non-transformed cultures. Antioxidant activity, as measured by 2,2-diphenyl-1-picryl-hydrazyl and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid-free radical scavenging assays, was significantly higher in hairy root cultures than in non-transformed cultures. Furthermore, the extract of hairy root culture showed inhibition of proliferation of human breast cancer cell line (MCF-7).