Identification by flow cytometry of Seiridin, one of the main phytotoxins produced by three Seiridium species pathogenic to cypress

Seiridin (SE), one of the main phytotoxins produced in vitro by Seiridium species pathogenic to cypress, was oxidized and the corresponding ketone derivative covalently linked to bovine serum albumin (BSA). The conjugate (SE-BSA) was used to prepare an antiserum to SE. The antibodies were absorbed with BSA and their specificity was assayed by ELISA and flow cytometry against SE, iso-seiridin (ISE), a structural isomer of SE, and some derivatives of these two metabolites. The antibodies tested in a competitive indirect ELISA did not show any binding activity to SE, ISE and their derivatives. The cytometry test, instead, was successful. SE-BSA and SE showed the highest binding activity with the antibodies. SE derivatives having a shift on the adjacent carbon, oxidation, or acetylation of the hydroxy group of the heptyl side chain at C-4 or conversion of the γ-lactone in the corresponding planar furane ring reacted less than SE. The 2′-dansylhydrazoneSE and the 3,4-dihydroSE having a bulky group attached to the heptyl side chain and a saturated lactone ring, respectively, showed a weak reactivity. SE derivatives in which the γ-lactone ring was destroyed and ISE derivatives presenting the shift of the hydroxy group at C-3′ and another structural modification had no binding activity