Catnip, <I>Nepeta cataria</I> (Lamiales: Lamiaceae)—A Closer Look: Seasonal Occurrence of Nepetalactone Isomers and Comparative Repellency of Three Terpenoids to Insects

Abstract

Evidence of repellent properties in catnip, Nepeta cataria L., to flies and cockroaches was observed in preliminary studies. This study compared catnip essential oil from steam distillation and elemol, a major constituent of osage orange essential oil, to current commercial repellents. These comparative studies found both the catnip steam distillate and elemol to be as good, and in some cases better, at repelling house flies, Musca domestica L., and American cockroaches, Periplaneta americana L., than N,N-diethyl-m-toluamide (DEET) or citronellal. Both short-term and long-term repellency bioassays were used to assess repellency. Catnip essential oil showed greater repellency than DEET and citronellal in the short term. Extended repellency bioassays showed elemol to be more repellent than catnip steam distillate, citronellal, and DEET. Nepetalactone, the major constituent of catnip essential oil, is present as two isomers, and previous studies have shown the E,Z-nepetalactone [2-(2-hydroxy-1-methylethenyl)-5-methyl-cyclopentanecarboxylic acid delta lactone] isomer to be even more repellent to cockroaches than the dominant isomer, Z,E-nepetalactone. This study examined the seasonal variation of the two isomers, Z,E-and E,Z-nepetalactone, in catnip. Samples of fresh catnip mature leaves, immature leaves, and stems were steam-distilled separately, and isomer composition was analyzed using high-performance liquid chromatography and gas chromatography (GC). An analysis of variance (ANOVA) showed significant differences by week. The mature leaf essential oil samples were tested in a repellency bioassay and exhibited significant repellency to German cockroaches, Blattella germanica L. The catnip floral volatiles were sampled using solid phase microextraction, and analysis with GC/ mass spectrometry showed the presence of Z,E-nepetalactone, E,Z-nepetalactone, and β-caryophyllene as the major constituents. Phytophagous insects and potential pollinators present on sampling dates were recorded.ABSTRACT Evidence of repellent properties in catnip, Nepeta cataria L., to ßies and cockroaches was observed in preliminary studies. This study compared catnip essential oil from steam distillation and elemol, a major constituent of osage orange essential oil, to current commercial repellents. These comparative studies found both the catnip steam distillate and elemol to be as good, and in some cases better, at repelling house ßies, Musca domestica L., and American cockroaches, Periplaneta americana L., than N,N-diethyl-m-toluamide (DEET) or citronellal. Both short-term and long-term repellency bioassays were used to assess repellency. Catnip essential oil showed greater repellency than DEET and citronellal in the short term. Extended repellency bioassays showed elemol to be more repellent than catnip steam distillate, citronellal, and DEET. Nepetalactone, the major constituent of catnip essential oil, is present as two isomers, and previous studies have shown the E,Z-nepetalactone [2-(2-hydroxy-1-methylethenyl)-5-methyl-cyclopentaneca...

Repellency of α-pinene against the house fly, Musca domestica

“…DEET, one of the most widely used insect repellents against biting arthropods, is minimally effective against the non-biting house fly as shown here and by others (Schultz et al, 2004). DEET's mode of action is still not fully resolved and while its interactions with olfactory and gustatory receptors may prevent insects from detecting and biting mammalian hosts (Ditzen et al, 2008;Lee et al, 2010;Pellegrino et al, 2011), these interactions may not be appropriate to dissuade a house fly from landing and depositing pathogenic microorganisms on inanimate objects.…”

Stereoselective Chemical Defense in the Drosophila Parasitoid Leptopilina heterotoma is Mediated by (−)-Iridomyrmecin and (+)-Isoiridomyrmecin

“…The mode of action of iridomyrmecin as repellent or insecticide and its physiological effects are unknown. Despite iridomyrmecin being a rather rare natural product, structurally related iridoids such as actinidine, iridodial, and nepetalactone are more widespread and are found in the defensive secretions of a number of insects (e.g., Wheeler et al, 1977;Jefson et al, 1983;Tomalski et al, 1987;Huth and Dettner, 1990) and plants (e.g., catnip Nepeta cataria, Schultz et al, 2004). Furthermore, iridoid-glycosides are common secondary plant metabolites, and are as such part of the plants' defense strategy against insect herbivores.…”

Fast gas chromatography characterisation of purified semiochemicals from essential oils of Matricaria chamomilla L. (Asteraceae) and Nepeta cataria L. (Lamiaceae)

“…(catnip oil) (Lamiaceae) [17,18]. Another isomer of nepetalactone (E,Z)-form, is present in small proportions in the catnip essential oil and is reported to be repellent to cockroaches [18].…”