Photosynthetic Inhibitory Activity of Dihydro-β-agarofurans Sesquiterpenes from Maytenus disticha and Maytenus boaria (Celastraceae)

Abstract

The effects of 9β-benzoyloxy-lå, 2å, 6β, 8å, 15-pentaacetoxy-dihydro-β-agarofuran and 9β- furoyloxy-lå, 6β, 8å-triacetoxy-dihydro-β-agarofuran, major phytogrowth inhibitors isolated from the aerial parts of Maytenus disticha (Celastraceae) and seeds of Maytenus boaria (Cel- astaraceae), respectively, on different photosynthetic activities of isolated spinach chloroplasts have been investigated. Photophosphorylation and electron transport (basal, phosphor- ylating and uncoupled) were inhibited in a concentration dependent manner by both compounds, therefore acting as Hill reaction inhibitors. The site of action of these natural compounds was located in the span from P680 to QA. 9β-benzoyloxy-l,2,6,8,15-pentaacetoxy- dihydro-β-agarofuran was one order of magnitude more potent (I50 = 2.6 μm) than 9β-furoy- loxy-l,6,8,-triacetoxydihydro-β-agarofuran, suggesting that the substitution at C-9 and the acetoxy groups at carbons 2 and 15 are important structural requirements for the displayed inhibitory activity. © 2000, Verlag der Zeitschrift für Naturforschung. All rights reserved.