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ARS Home » Southeast Area » Oxford, Mississippi » Natural Products Utilization Research » Research » Publications at this Location » Publication #138531
Title: PS II INHIBITORY ACTIVITY OF RESORCINOLIC LIPIDS FROM SORGHUM BICOLOR

Author
item Rimando, Agnes
item Dayan, Franck
item STREIBIG, JENS - ROYAL AG/VET UNIV-DENMARK

Submitted to: Journal of Natural Products
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/3/2002
Publication Date: 1/2/2003
Citation: Rimando, A.M., Dayan, F.E., Streibig, J.C. 2003. Ps ii inhibitory activity of resorcinolic lipids from sorghum bicolor. Journal of Natural Products. 66:42-45.

Interpretive Summary: One known and two new resorcinolic lipids were isolated from the root extracts of Sorghum bicolor. The known compound was 4,6-dimethoxy-2-[(8Z,11Z)-8,11, 14-pentadecatriene] resorcinol (4). The two new compounds were analogues of 4 and were identified as 4-methoxy-6-ethoxy-2-[(8Z,11Z)-8,11,14-pentadecatriene]resorcinol (5), and 4-hydroxy-6-ethoxy-2-[(10Z,13Z)-10,13,16-heptadecatriene]resorcinol (6). Compounds 4 and 5 inhibited photosynthetic oxygen evolution (IC50 0.09 and 0.20 uM, respectively) with activity similar to that of sorgoleone, the major sorghum phytotoxin. Compound 4 could not be enzymatically converted into a quinone, suggesting that its activity does not require the presence of the quinone functionality, and that it may exert inhibition by some other mechanisms. Compound 4 also inhibited lettuce seed germination, with activity greater than that of sorgoleone at lower concentrations. This is the first report on phytotoxic and PSII inhibitory activities of compound 4, and for resorcinolic lipids as a class of compounds.

Technical Abstract: Resorcinolic lipids were isolated from the root extracts of Sorghum bicolor and identified as 4,6-dimethoxy-2-[(8Z,11Z)-8,11,14-pentadecatriene]resorcinol (4), 4-methoxy-6-ethoxy-2-[(8Z,11Z)-8,11,14-pentadecatriene]resorcinol (5), and 4-hydroxy-6-ethoxy-2-[(10Z,13Z)-10,13,16-heptadecatriene]resorcinol (6). Compounds 4 and 5 inhibited photosynthetic oxygen evolution (IC50 0.09 and 0.20 uM, respectively). Compound 4 could not be enzymatically converted to a quinone, suggesting that the quinone moiety is not required for its photosystem II inhibitory activity. This is the first report for this activity of 4. Compounds 5 and 6 are also being reported for the first time.