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      Chemical investigation of phytoalexins and phytoanticipins : isolation, synthesis and antifungal activity

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      Date
      2007
      Author
      Sarwar, Md Golam
      Type
      Thesis
      Degree Level
      Masters
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      Abstract
      The focus of my research was on the secondary metabolites produced by crucifer plants under stress and their biological activity against fungi. Both cultivated and wild plants were investigated to isolate phytoalexins and phytoanticipins, and determine their metabolite profiles.The first chapter of this thesis describes cruciferous plants and their most important pathogenic fungi. These plants are divided into three groups: oilseeds, vegetables and wild species. The metabolites isolated from these plants and their biosynthetic studies are reviewed. In addition economically important necrotrophic fungi such as Leptosphaeria maculans, Alternaria brassicae, Sclerotinia sclerotiorum and Rhizoctonia solani are also reviewed along with their phytotoxins. The second chapter of this thesis describes the detection, isolation, structure determination, syntheses of stress metabolites and biological activity of these metabolites against L. maculans, S. sclerotiorum and R. solani. The investigation of cauliflower led to the isolation of seven phytoalexins: 1-methoxybrassitin (55), spirobrassinin (71), isalexin (64), brassicanal C (60), caulilexins A (106), B (107), and C (105). The phytoalexins caulilexins A (106), B (107) and C (105) were reported for the first time. Caulilexin A (106), having a disulfide bridge, showed the highest activity against S. sclerotiorum and R. solani among the known phytoalexins. Similarly four phytoalexins: 1-methoxybrassitin, brussalexins A (121), B (117) and C (118) along with four metabolites: ascorbigen (51), diindolylmethane (50), 1-methoxy-3,3’-diindolylmethane (119) and di-(1-methoxy-3-indolyl)methane (120) were isolated from Brussels sprouts. The phytoalexins brussalexins A (121), B (117) and C (118) are new metabolites. Brussalexin A (121) is the only cruciferous phytoalexins having an allyl thiolcarbamate functional group. The metabolite 1-methoxy-3,3’-diindolylmethane (119) is reported for the first time.The investigation of brown mustard for polar metabolites led to the isolation of indole-3-acetonitrile (76) and spirobrassinin (71) along with isorhamnetin-3,7-diglucoside (134). Investigation of wild species such as Asian mustard, sand rocket, wallrocket, hedge mustard and Abyssinian mustard for production of stress metabolites led to the isolation of indole-3-acetonitrile (76), arvelexin (84), 1,4-dimethoxyindole-3-acetonitrile (137), rapalexins A (138) and B (142), methyl-1-methoxyindole-3-carboxylate (59) and metabolites bis(4-isothiocyanotobutyl)-disulfide (139), 5-(3-isothiocyanato-propylsulfanyl)-pentylisothiocyanate (136) and 3-(methylsulfinyl)-propylisothiocyanate (135). Two metabolites were also isolated from Brussels sprouts and brown mustard; however, these structures are not yet determined. The metabolites 1,4-dimethoxyindole-3-acetonitrile (137) and 5-(3-isothiocyanato-propylsulfanyl)-pentylisothiocyanate (136) are reported for the first time.
      Degree
      Master of Science (M.Sc.)
      Department
      Chemistry
      Program
      Chemistry
      Supervisor
      Pedras, M. Soledade C.
      Copyright Date
      2007
      URI
      http://hdl.handle.net/10388/etd-08022007-142117
      Subject
      cauliflower
      Brussels sprouts
      phytoalexins
      wild cricifer
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