Phytotoxins from Hofmeisteria schaffneri:: Isolation and synthesis of 2′-(2-hydroxy-4-methylphenyl)-2′-oxoethyl acetate

Activity-directed fractionation of a CH2Cl2-MeOH (1:1) extract of Hofmeisteria schaffneri led to the isolation of a new phytotoxin characterized as 2'-(2-hydroxy-4-methylphenyl)-2'-oxoethyl acetate and designated the trivial name of hofmeisterin (1). In addition, the known compounds beta-carotene, euparin, and 3',4',4a',9a'-tetrahydro-6,7'-dimethylspiro[benzofuran-3(2H),2'-pyrano[2,3-b]benzofuran]-2,4a'-diol (2) were obtained. The identification of the isolates was accomplished by spectroscopic methods. The structure of 1 was unequivocally confirmed by synthesis. The methyl derivative la was also synthesized following the same strategy. Compounds 1 and 2 inhibited radicle growth of Amaranthus hypochondriacus (IC50 = 3.2 x 10(-4) and 1.2 x 10(-5) M, respectively) and significantly inhibited activation of the calmodulin (CaM)-dependent enzyme cAMP phosphodiesterase (PDE) with IC50 values of 4.4 and 4.22 mu M, respectively.