Furanocoumarin with Phytotoxic Activity from the Leaves of Amyris elemifera (Rutaceae)

Bioassay-guided fractionation of the ethyl acetate extract of Amyris elemifera leaves was carried out to identify phytotoxic and antifungal constituents. A novel phytotoxic furanocoumarin 8-(3-methylbut-2-enyloxy)-marmesin acetate (1) and its deacyl analog 8-(3-methylbut-2-enyloxy)-marmesin (2) were isolated. The X-ray crystal structure determination is reported for the first time for 1. Both 1 and 2 have the S configuration at C-2′ based on X-ray crystallographic data. Both these compounds inhibited the growth of the dicot Lactuca sativa (lettuce) and the monocot Agrostis stolonifera with a more pronounced inhibitory effect on the monocots at 330 μM by 1. In Lemna paucicostata Hegelm phytotoxicity bioassay, the IC₅₀ value for 1 was 26 μM, whereas 2 had an IC₅₀ value of 102 μM. Compounds 1 and 2 were weakly antifungal against Colletotrichum fragariae Brooks in TLC bioautography.