88(P2-18) カンキツ黒斑病菌tangerine pathotypeが生産するACT毒素の構造と宿主特異性に関する化学的考察(ポスター発表の部)  [in Japanese] 88(P2-18) CHEMICAL STUDIES ON STRUCTURES AND HOST-SPECIFICITIES OF ACT-TOXINS PRODUCED BY ALTERNARIA ALTERNATA TANGERINE PATHOTYPE CAUSING CITRUS BROWN SPOT DISEASE  [in Japanese]

ACT-toxin AI and AIII are host-specific toxins produced by Alter-naria alternata tangerine pathotype causing citrus brown spot disease in USA. They were isolated from both culture filtrates and spore germinating fluid of the toxin producer and the chemical structures were elucidated to be 6 and 7, which contain the conjugated carboxylic acid moieties found in AK-toxins (4 and 5) and AF-toxins (1, 2 and 3) produced by A. alternata Japanese pear pathotype and strawberry pathotype, respectively. We suppose that ACT-toxin AI is an original form produced by enzyme system of the fungus and ACT-toxin AII is an artifact originated by photochemi-c al isomerization of ACT-toxin AI. They exibited potent toxicitiesn of only to the host-plant (citrus) but also to the other plant (Japanese pear). Conjugated acid derivatives, 13b and 13c, were also isolated from culture filtrates of ACT-toxins producer and identified witht he authentic samples isolated from both culture filtrates of AK-toxins producer and AF-toxin producer. Since the decatrienoic acid 13 had been determined to be a biological precursor of AK-toxins, biosynthetic pathway of AK-toxins, AF-toxins and ACT-toxins must be very similar as shown in the scheme.