Toxicity and plant growth regulator effects of cytochalasin H isolated from Phomopsis sp.

A biologically active metabolite was found in crude extracts of an unidentified species of Phomopsis isolated from weevil-damaged pecans. Purified metabolite was toxic to day-old cockerels, with an LD 50 of 12.5 mg/kg, and was markedly inhibitory to growth and floral development of tobacco plants at concentrations of 10 −2 to 10 −4 M. IR and 1 H-nmr spectra indicated an alkylphenyl moiety with a single nitrogen atom present as a secondary amide: and acetate ester, OH, CH 3 , and a trans-double bond function. Elemental and high-resolution mass-spectral analysis indicated a formula of C 30 H 39 NO 5 and a molecular weight of 493.2886. The metabolite was identified as cytochalasin H.