chlorophyll-a and sorgoleone

Our study of the mechanism(s) by which sorgoleone (1) acts as a photosystem II (PS II) inhibitor led to the isolation of a new benzoquinone derivative, 2-hydroxy-5-ethoxy-3-[(Z,Z)-8',11', 14'-pentadecatriene]-rho-benzoquinone (2), from the root exudate of sorghum. The structure of 2, which is being given the name 5-ethoxy-sorgoleone, was determined by spectroscopic means. A methoxy derivative (3) of 1 was also prepared. Both 2 and 3 caused a reduction in oxygen evolution by thylakoid membranes and induced variable chlorophyll fluorescence. These compounds, however, were less active inhibitors of PS II than 1.

Topics: Benzoquinones; Carbohydrate Sequence; Chlorophyll; Electron Transport; Herbicides; Lipids; Magnetic Resonance Spectroscopy; Mass Spectrometry; Molecular Sequence Data; Oxygen; Photosynthesis; Plants, Medicinal; Spectrophotometry, Infrared; Spectrophotometry, Ultraviolet; Spinacia oleracea