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Arylnaphthalene and aryltetralin-type lignans in hairy root cultures of Linum perenne, and the stereochemistry of 6-methoxypodophyllotoxin and one diastereoisomer by HPLC-MS and NMR spectroscopy.

INTRODUCTION
Hairy root cultures of Linum sp. are an alternative for the high production of lignans. Linum perenne is known to produce arylnaphthalene-type lignans such as justicidin B, isojusticidin and diphyllin.


OBJECTIVE
To elucidate the presence of aryltetralin-type lignan diastereoisomers, besides the known arylnaphthalene-type lignans, in hairy roots of Linum perenne, and to determine the configurations of one diastereoisomer of 6-methoxypodophyllotoxin (6-MPTOX).


METHODS
Lignans from hairy root cultures of Linum perenne were extracted and separated by HPLC. Arylnaphthalene-type lignans were identified by LC-MS, according to the literature. Two diastereoisomers of aryltetralin-type lignans were analysed by mass spectrometry and NMR spectroscopy.


RESULTS
Numerous arylnaphthalene-type lignans (diphyllin-2-hexose-pentose, diphyllin-3-pentose and diphyllin-hexose) were identified in hairy root cultures. Methoxypodophyllotoxin, an aryltetralin-type lignan, was also identified, as well as one diastereoisomer. This aryltetralin-type lignan could be derived via 7-hydroxymatairesinol as a hypothetical biosynthetic pathway. The stereochemical configurations of aryltetralin isomers were determined.


CONCLUSION
Arylnaphthalene and two diastereoisomers of aryltetralin-type lignans are produced in Linum perenne hairy root cultures. Matairesinol, the precursor of justicidin B, also seems to be converted into 6-MPTOX via 7-hydroxymatairesinol. This is the first report of the stereochemical configurations of an aryltetralin-type lignan other than podophyllotoxin (PTOX).