• Korean Journal of Weed Science
• /
• v.15 no.1
• /
• pp.85-98
• /
• 1995

Six malformin B's produced by Aspergillus niger van Tiegh. were separated by HPLC. Their structures determined by the methods of amino acid analyses, mass spectrometry, and two-dimensional NMR were revealed as cyclic pentapeptides structurally related to malformin $A_1$. Both the NMR and MS/MS data suggest that the respective structures of separated malformin B's were as follows; cyclo-D-Cys-D-Cys-L-Val-D-Leu-L-allo-Ile for $B_{1a}$, cyclo-D-Cys-D-Cys-L-Val-D-Leu-L-Leu for $B_{1b}$, cyclo-D-Cys-D-Cys-L-Val-D-Val-L-Leu for $B_2$, cyclo-D-Cys-D-Cys-L-Val-D-Ile-L-Leu for $B_3$, cyclo-D-Cys-D-Cys-L-Val-D-Ile-L-Ile for $B_4$, and cyclo-D-Cys-D-Cys-L-Val-D-Val-L-Ile for $B_5$. Among the malformin B's, the structure of $B_{1b}$ was the same as that of malformin $A_3$ or C. All the malformin B's showed physiological activities in the two assay systems using corn(Zea mays L.) roots and mung bean(Phaseolus aureus Roxb.) hypercotyl segments. The malformin B's with molecular weight 529 were more effective for inducing corn root curvature than those with molecular weight 515. The difference in molecular weight of malformin B's, i.e., the retention time on HPLC, results in the polarity change of the whole malformin molecule which affects the revealation of the malformin activities. In addition, the disulfide form of the malformin B's gives the rigidity of the molecule, whereas the combination of the fourth and the fifth amino acid residues provides the optimal three-dimensional configuration to the malformin receptor of plants. Presumably, these two factors are appeared to be essential for the greatest physiological activity of malformin B's. malformin $B_{1a}$ caused the corn root curvature by 90% at a concentration of $0.25{\mu}M$. However, such differential activities with molecular weight of 529 or 515 of malformin B's were not found in the mung bean hypercotyl segment test. Maximum stimulation of mung bean hypercotyl growth was observed at $0.1{\mu}M$ concentration of malformin B's. The growth of the segments treated with $B_5$ was 154% greater than that of the control.

• Korean Journal of Weed Science
• /
• v.15 no.1
• /
• pp.73-84
• /
• 1995

Four malformin A's produced by Aspergillus niger van Tiegh. were separated by HPLC equipped with $C_{18}$ reversed-phase column and subjected to structural determination. Amino acid analyses and mass spectra data of the compounds indicate that they structurally resemble the cyclic pentapeptide malformin $A_1$. Their structures were deduced by two dimensional NMR and MS/MS experiments as cyclo-D-Cys-D-Cys-L-Val-D-Leu-L-Ile for $A_1$, cyclo-D-Cys-D-Cys-L-Val-D-Leu-L-Val for $A_2$, cyclo-D-Cys-D-Cys-L-Val-D-Leu-L-Leu for $A_3$, and cyclo-D-Cys-D-Cys-L-Val-D-Ile-L-Val for $A_4$. Among the mal-formin A's, the structure of $A_3$ was identical to that of malformin C, which was produced by A. niger strain AN-1. All the malformin A's caused severe curvatures of corn(Zea mays L.) roots and the activities of the malformin A's with molecular weight 529 were greater than those with molecular weight 515. Malformin $A_1$ caused the corn root curvature by 83% at a concentration of $0.25{\mu}M$. In the mung bean(Phaseolus aureus Roxb.) hypercotyl segment test, however, the molecular weight of malformin A's was not a factor influencing the physiological activities. Malformin $A_1$ stimulated the growth of mung bean hypercotyles by 165% at a $0.1{\mu}M$ concentration.