CHARACTERIZATION OF ACTIVE COMPOUNDS IN RESISTANCE-INDUCING PLANT EXTRACTS OF REYNOUTRIA SACHALINENSIS
A SCHMITT1, KH GANSBAUER2, O VOSTROWSKI2, J HUBER1 and HJ BESTMANN2
1Biological Research Centre for Agriculture and Forestry, Institute for Biological Control, 64287 Darmstadt, Germany; 2FA-University Eriangen-Nornberg, Institute for Organic Chemistry, 91054 Eriangen, Germany
Background and objectives
Results and conclusions
The HPLC profile of the two resulting fractions showed that after hydrolysis the number and height of peaks were enhanced to a large extent. Also, on thin layer chromatograms (TLC) the unhydrolysed methanol fraction could not be separated in the given solvent system, whereas after hydrolysis two yellow bands could be seen. These bands and the rest of the TLC plate were re-eluted and bioassayed against S. fuliginea on cucumber. Band 1 reached an efficacy of 83%, while band 2 and the rest of the TLC plate had no influence on the development of the pathogen. Investigations by GC-MS and comparison with known compounds led to the identification of the two anthrachinones physcion (band 1) and emodin (band 2). Bioassays on cucumber with synthetically produced physcion and emodin supported these findings: only physcion reduced the development of powdery mildew on cucumbers, while emodin did not. Both compounds could be identified in the HPLC profile of the hydrolysed, but not in the unhydrolysed methanol extract, indicating that the aglyca have been released by acid hydrolysis from a bonded form. In literature there are reports on the occurrence of physcion and emodin and their glycosides in R. sachalinensis. Therefore the activity in this fraction could either be due to the physcion glycoside or to other compounds not yet determined. Further investigation will be necessary to clarify this question.