Purification And Chemical Structure Of The Selective Mycotoxin Fraction Produced By Exserohilum Turcicum

Northern Leaf Blight of corn (NLBC) is a major leaf disease in com planting. A lot of reseaches indicated that the pathotoxin (HT-toxin) produced by Exserohilum turcicum was the important reason causing this disease.The best isolating and purificating conditions for HT-toxin based on following standrads such as isolating spectrum> peak height and peak area have been studied using high performance liquid chromatography(HPLC). The results were as follows: hyperpure water could be used as mobile phase to isolate HT-toxin; UV detection had high sensitivity between 254nm and 269nm, that was convenient to observe and to prepare toxin fractions; the pH value of mobile phase had largely effect on separating degree of HT-toxin , and every peak had good separating degree at pH3.25; in control test, mobile phase hadn' t any UV absorption in the condition of detective wavelength range and the best suitable pH value. 1.8mL/min was chosed as the flow rate of mobile phase, and 2% methanol was added after 57 minutes in the test. Thus it needed 80 minutes to finish the seperation, and 13 fractions could be isolated from HT-toxin.The bioassay results to every fraction using acupuncturing leaves in vitro manifested that fraction K fraction 3 (mixture fraction) and fraction 6 had different toxicity to corn. The lesion areas on OH43Ht; produced by fraction 3 and fraction 6 were larger than that on other corns. Fraction 6 and HT-7 which was a selective fraction isolated in former test were the same fraction through HPLC analysis. Moreover, some nontoxic frations were also isolated in this test and the qualitative analysis of fraction 6 was done,,The experimental results showed that the retention time of standard toxin fraction ( 5-hydroxymethyl-2-furancarboxaldehyde) was the same as that of fraction 8 isolated in this test by HPLC.On the basis of HPLC analysis, the active fractions were prepared, and the identification of chemical structural of fraction 1 and fraction 6 have preliminary been done by MS^ NMR and IR analysis. Fraction 1 was supposed as a saccharide which has -CH3x -CH2- ^ -C-O-and some others, and it' s molecular weight was 163. Fraction 6 was likely a compound having-C=C-, -C=(K -CH2- , and it' s molecular weight might59be 142. The specific chemical structure should be analyzed and identified ulteriorly.