Enhanced Aryltetralin Lignans Production in Linum Adventi-Tious Root Cultures.

Lignans are the main secondary metabolites synthetized by Linum species as plant defense molecules. They are also valuable for human health, in particular, for their potent antiviral and antineoplastic properties. In this study, the adventitious root cultures of three Linum species (L. flavum, L. mucronatum and L. dolomiticum) were developed to produce aryltetralin lignans. The effect of two elicitors, methyl jasmonate and coronatine, on aryltetralin lignans production was also evaluated. The adventitious root cultures from L. dolomiticum were obtained and analyzed for the first time and resulted as the best producer for all the aryltetralins highlighted in this system: Podophyllotoxin, 6-methoxypodophyllotoxin and 6-methoxypodophyllotoxin-7-O-ß-glucoside, the last showing a productivity of 92.6 mg/g DW. The two elicitors differently affected the production of the 6-methoxypodophyllotoxin and 6-methoxypodophyllotoxin-7-O-ß-glucoside.

Investigation of Linum flavum (L.) Hairy Root Cultures for the Production of Anticancer Aryltetralin Lignans.

Linum flavum hairy root lines were established from hypocotyl pieces using Agrobacterium rhizogenes strains LBA 9402 and ATCC 15834. Both strains were effective for transformation but induction of hairy root phenotype was more stable with strain ATCC 15834. Whereas similar accumulation patterns were observed in podophyllotoxin-related compounds (6-methoxy-podophyllotoxin, podophyllotoxin and deoxypodophyllotoxin), significant quantitative variations were noted between root lines. The influence of culture medium and various treatments (hormone, elicitation and precursor feeding) were evaluated. The highest accumulation was obtained in Gamborg B5 medium. Treatment with methyl jasmonate, and feeding using ferulic acid increased the accumulation of aryltetralin lignans. These results point to the use of hairy root culture lines of Linum flavum as potential sources for these valuable metabolites as an alternative, or as a complement to Podophyllum collected from wild stands.

Aryltetralin lignans from Hyptis brachiata inhibiting T lymphocyte proliferation.

Increased activation and proliferation of T lymphocytes plays an essential role in the development of chronic inflammation and autoimmune diseases. Currently used immunosuppressive drugs often do not provide long-lasting relief of symptoms and show a gradual loss of efficacy over time, and are accompanied by various side effects. Therefore, novel immunosuppressive lead substances are needed. For this purpose, an in-house library consisting of 600 extracts of plants from Panama was screened for inhibition of human T lymphocyte proliferation. As one of the hits, an ethyl acetate extract from the aerial parts of Hyptis brachiata (Lamiaceae) exhibited strong inhibitory effects. Subsequent investigation resulted in the isolation of seven aryltetralin lignans, five arylnaphthalene lignans, two flavonoids, three triterpenes, and cinnamyl cinnamate. Aryltetralin lignans inhibited T lymphocyte proliferation in a concentration-dependent manner without induction of apoptosis. No relevant inhibition was observed for the arylnaphthalene lignans, flavonoids, and triterpenes. Additional cell cycle arrest investigations revealed that isolated aryltetralin lignans potently inhibited cell division in G2/M phase similarly to podophyllotoxin. Multifluorescence panel analyses of the extract also showed weak suppressive effects on the production of IL-2 and TNF-α. Therefore, preparations made out of H. brachiata could be further explored as an interesting herbal alternative in the treatment of autoimmune diseases.

Kinetics of glucosylated and non-glucosylated aryltetralin lignans in Linum hairy root cultures.

Due to their pronounced cytotoxic activity, a number of aryltetralin lignans (ATLs), such as podophyllotoxin (PTOX), are used as antitumor compounds. The production of such molecules from entire plants or plant cell-tissue-organ cultures is thus of interest to the pharmaceutical industry. Hairy root cultures constitute a good tool not only for phytochemical production but also for investigating plant secondary metabolism. This work reports on the growth and ATL biosynthesis in two hairy root cultures of Linum album Kotschy ex Boiss. and Linum flavum. The kinetics of accumulation of the intermediates of MPTOX biosynthesis and of their glucosylated forms are described over a 21-day period of growth. An accumulation of non-glucosylated forms of the ATLs during the exponential phase of the cultures is followed by an accumulation of the glucosylated forms during the stationary phase. Our results show a strong coordination of the biosynthetic paths derived from deoxypodophyllotoxin via deoxypodophyllotoxin 6-hydroxylase and deoxypodophyllotoxin 7-hydroxylase, and a coordinated glucosylation of podophyllotoxin, methoxypodophyllotoxin, and 5'-demethoxymethoxypodophyllotoxin. Furthermore, our results suggest an important role of ß-peltatin-6-glucoside formation in the control of ATL accumulation in Linum hairy root cultures.