ALLELOPATHIC POTENTIAL OF MENTHOFURAN MONOTERPENES FROM CALAMINTHA-ASHEI

A reversed-phase HPLC analysis was used to separate and quantify five menthofuran monoterpenes in Calamintha ashei leaf soaks and washes. ()-Evodone and desacetylcalaminthone were the major constituents of bot h soaks and washes. Concentrations of (+)-evodone and desacetylcalamin thone were as high as 0.66 and 0.74 mM, respectively, in leaf soaks. T he highest concentration of monoterpenes in leaf washes obtained by mi sting was 0.021 mM. Aqueous solubilities of the menthofurans were dete rmined to exceed concentrations required for growth inhibition. Bioass ays of individual Calamintha monoterpenes demonstrated effects on germ ination as low as 0.05 mM for (+)-evodone. An equimolar mixture of des acetylcalaminthone and (+)-evodone reduced Rudbeckia hirta germination by 17% at a combined concentration of 0.025 mM for Leptochloa dubia. Confirmation of allelopathic effects by Calamintha ashei will require long-term bioassays of Calamintha menthofurans on the growth of native sandhill species under conditions comparable to the harsh environment of the Florida scrub.