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United States Department of Agriculture

Agricultural Research Service

Title: A New Photosystem II Electron Transfer Inhibitor from Sorghum

Authors
item Rimando, Agnes
item Dayan, Franck
item Czarnota, M - UNIV OF KENTUCKY
item Weston, L - UNIV OF KENTUCKY
item Duke, Stephen

Submitted to: Journal of Natural Products
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 4, 1998
Publication Date: N/A

Interpretive Summary: A new natural product was isolated from root exudates of sorghum. It is an analog of sorgoleone, a natural herbicide produced by sorghum. A similar synthetic compound was also produced. These compounds were found to inhibit photosynthetis. Their biological and molecular activities were compared to the synthetic herbicide atrazine. The new compounds had either similar or greater activity than atrazine, but were less active than sorgoleone.

Technical Abstract: 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]-r-benzoquinone (2),from the root exudate of sorghum [Sorghum bicolor (L.) Moench (Poaceae)]. 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. However, these compounds were less active inhibitors of PS II than 1. These observations indicate that modifying the 3-hydroxy and 5-methoxy substituents of 1 affects its inhibitory activity.

Last Modified: 8/30/2014