1. Malformins Produced by Aspergillus niger Malformins induces root curvatures on corn plants and malformations on bean plants with other biological activities. Malformins were separated on HPLC and were served for structural determinations. Amino acid analyses and mass spectra suggested that all of them structurally resembled to cyclic pentapeptide malformin A₁. Two dimensional NMR experiments and MS/MS experiments led to deduce cyclo-D-cysteinyl- D-cysteinyl-L-amino acid-Damino acid-L-amino acid for the, essential structure of malformins. Both their structures and phytoactivities will be described. (그림) 2. Phytoxins Produced by Drechslera portulacae A fungal plant pathogen, Drechslera portulacae, is a causal agent of leaf spot of purslane (Portulaca oleracea) which is a noxious worldwide weed. Zearalenone derivatives (methyldihydroxyzearalenone 1 and zeaenol 2) have been isolated from this fungus, and the relative configuration of zeaenol was determined by single-crystal X-ray diffraction method together with assignments of ¹H and ^(13)C NMR spectra. Both compounds exhibited phytoactivity in two bioassay test systems. (그림)