Identification And Bioassay Of Herbicidal Active Compounds From Alternaria Amaranthi

In order to obtain new herbicidal activity compound, four pesticides was add to the liquid medium thatwas used for the fermentation of Alternaria amaranthi. The result showed that the fermentation broth ofAlternaria amaranthi cultured in bentazone medium have a higher herbicidal activeity against Amaranthusretroflexus L. than that of the mixture of bentazone and fermentation broth of Alternaria amaranthi. Basedon the reault, we guessed that there could have a herbicidal activeity compounds in the co-culture fermentationbroth. For the identification of herbicidal activeity compounds, the methods of column chromatography andthin layer chromatography were use in the experiment, and gas chromatography with mass spectrometry wasuseed to analyze the structure of herbicidal activeity compounds. The fermentation medium was optimized forincreasing the product rate of herbicidal activeity compounds. Conclusions are as follows.1.Compare with the mixture of fomesafen and fermentation broth of Alternaria amaranthi, the fermentationbroth of Alternaria amaranthi cultured in fomesafen medium do not show a significant activity for controllingthe Amaranthus retroflexus L. There are not significant difference between fermentation broth of Alternariaamaranthi cultured in fluorine sulfonamides the ether medium and the mixture of Alternaria amaranthi andfluorine sulfonamides the ether. However, the fermentation broth of Alternaria amaranthi cultured inbentazone medium have a higher herbicidal activeity against Amaranthus retroflexus L. than that of themixture of bentazone and fermentation broth of Alternaria amaranthi.2. The PSK medium is not suitable for the fermentation. The modified PSK medium not only acceleratefermentation process, but also increase the herbicidal activity of the fermentation broth. Therefore, themodified PSK medium was used for the experiment. The modified PSK medium is composed of PSK andpotato homogenate, but the glucose is not added in medium. The fermentation condition is25℃, pH6, and toensure adequate dissolved oxygen,at speed150rpm and7d.for culture.3. Herbicidal activity compound was isolated with column chromatography. The activity compound that waseluted with petroleum ether: ethyl acetate=1:5elution agent showed a highest herbicidal activity toAmaranthus retroflexus L. Thus, the activity compound was further isolated with a thin layer chromatographymethod. The9activity compounds were obtained in the experiment. All of the compound6and compound7significantly inhibited the seed germination and radicle growth of Amaranthus retroflexus L, and caused aobvious necrosis spot in leaves of by Amaranthus retroflexus L. The activity of he compound6and compound7was higher than that of bentazone.4. The method of gas chromatography with mass spectrometry was used to analyse the eluted component E.The result showed that there were15compounds from the petroleum ether: ethyl acetate=1:5eluent. BecauseThe one of15compounds have the molecular formula C₁₀H₁₂N₂O₃S, so it was identified as bentazon. Thecompound6was indentified as C₁₀H₁₄N₂O. For Si contamination. it is difficult to identify the molecularformula of the compound7therefore the compound7also need a process of repurification to obtain a newcrystal.