Novel chlorosis-inducing substances, AB5046Aand B, were isolated from the culture broth of a fungal strain. The producing organism, designated AB5046, was identified as a member of Nodulispor ium.AB5046Aand B were purified by extraction with EtOAc and silica gel chromatography. The structure of AB5046Aand B were determined to be 2-butyryl-3,5-dihydroxy-cyclohex-2-ene-l-one and 2-acetyl-3,5-dihydroxy-cyclohex-2-enel-one, respectively, by spectroscopic analyses. AB5046Aand B induced chlorosis against Japanese barnyard millet in vitro. The chlorosis activity of these compoundswas stronger against monocotyledonsthan dicotyledons. Inhibitionsof chloroplast formation, photosynthesis and essential amino acid's biosynthesis are considered as the important and attractive targets in the development of new herbicides with low toxicity to mammals. Some herbicides such as pyrazolate1}, methoxy-phenone2), fluridone3) are practically used as the inhibitors of chloroplast formation (chlorosis-inducing chemicals). Although it is known that some natural products (virdomic acids4), alternaric acid5), rhizobitoxin6), l -amino-2-nitrocyclopentanecarboxylic acid7), tentoxin8), etc.) have chlorosis-inducing activity, they are not utilized for control of weeds. In the course of screening for new herbicides, we found that a soil fungus produced new herbicidal substances, named AB5046A(1) and B (2), which induced chlorosis against Japanese barnyard millet in vitro. The color of generating foliage of the barnyard millet became completely white, as if they were bleached, whenthe seeds were treated with these compounds.In this paper, we describe the identification of the producing organism together with the isolation, fermentation, structure determination and biological activities of 1 and 2. Materials and Methods TaxonomyThe AB5046Aand B producing organism, strain AB5046, was isolated from a soil sample collected at Seta-gun in Gummaprefecture. Morphological observations of the strain grownon malt extract agar were carried out with a light microscope (Olympus Model BHS) and a scanning electron microscope (Hitachi S-430). The characteristics of the culture on potato -dextrose agar and malt extract agar were determined after 2 weeks of incubation

AB3217-A, a novel anti-mite substance, was isolated from the fermentation broth of a streptomycete strain. The strain was isolated from a soil collected at Kita-azumi, NaganoPrefecture, Japan, and identified as Streptomyces platensis AB3217. AB3217-A was purified by Amberlite IR120B, Diaion HP-20 and CM-Sephadex C-25 column chromatographies. The molecular formula was determined as C17H23NO7 by elemental analysis, MSand 13C NMRspectroscopy. The structure of AB3217-A was determined to be (IR,3S,4S,-7/?,8i?,l l i?,125',137?)-4,12,13-trihydroxy-8-(4-methoxyphenyl)-6-aza-2,9,14-trioxatncyclo-[9.2. 1.03i7]tetradecane by spectroscopic analysis and X-ray crystallographic analysis. The molecule of AB3217-Ahas unique structure that deacetylanisomycin and /?-D-xylofuranose linked through glycosidic bond and ether bond resulting in the formation of nine-membered ring. AB3217-Ashowed marked activity against the two spotted spider mite, Tetranychus urticae.