Insecticidal chromenes from the Asteraceae: structure-activity relations

Abstract

Chromenes (benzopyrans), common to many genera of the Asteraceae, are lethal to the neonate variegated cutworm, Peridrorna saucia Hiibner, when presented on the inner walls of glass vials at concentrations of 1.0 #mol/vial or less. Closely related benzofurans, including some from the same plants, are relatively inactive at these concentrations. The most potent of seven naturally-occurring and four derived chromenes is the well known allatocidin, precocene II, with an LDs0 of 0.134 t~mol/vial or 0.67 #g/cm 2. A more widely distributed chromene, desmethoxyencecalin, is also relatively toxic with an LDs0 of 0.98 #g/cm 2.Structure-activity comparisons of the chromenes tested in this study suggest that the presence of a free hydroxyl group at either C-7 or C-11 significantly diminishes activity. Saturation of the 3,4 double bond, which destroys the allatocidal activity of the precocenes, diminishes, but does not alleviate, contact toxicity of chromenes to cutworm larvae. Brief exposure (24 h) of 2-day-old larvae to chromene residues significantly inhibits subsequent larval growth. The degree of chronic growth inhibition (sublethal toxicity) from five different chromenes is highly correlated to their lethal potencies to neonate larvae.

Influence of light on plant allelochemicals: A synergistic defense in higher plants

“…The chrornenes from Piper hostmamianurn [46], an amazonian shrub, are structurally similar to chromenes from members of the Asteraceae which are phototoxic to various microbes [47] and insects [47,48]. Studies are under way to determine the identity of the antimicrobial metabolites in the genus Piper, and whether they are effective insecticides as is the ease with many other plant-derived phototoxins (see [l-31 and [14] for discussions of the broadspectrum toxicity of plant phototoxins).…”

Molluscicidal activity of vulgarone B against ram's horn snail (Planorbella trivolvis)

“…Vulgarone B has been reported as a gastropod repellant, and this has led us to test it for the molluscicidal activity 6. Plants in the family Asteraceae possess compounds with many biological activities, including phytotoxic, antifungal and insecticidal activities 7–11. Our preliminary bioassay of vulgarone B and the steam‐distilled oil of A douglasiana indicated lethal activity against P trivolvis .…”

Metabolism and excretion of acetylchromenes by the migratory grasshopper

“…), is insecticidal to a wide range of insect species [3-61, including some considered insensitive to the antihormonal effects of the precocenes. In our previous investigations of structureactivity relations for the insecticidal actions of acetylchromenes [6,7], we found that compounds possessing free hydroxyl groups were significantly less toxic to both cutworms and grasshoppers. In particular, the 7-demethyl derivative of encecalin (2) is significantly less toxic than encecalin in insects from four different orders so far tested [4-61. In the present report, we investigate differences in pharmacokinetics and metabolism between encecalin and DME* in the migratory grasshopper, Melanoplus sanguinipes.…”