Nicanor J. Liquido

Saturated and monofluoro analogs of the oriental fruit fly attractant methyl eugenol show reduced genotoxic activities in yeast

Methyl eugenol, is a commercially used fruit fly attractant and a suspected carcinogen. Several phenylpropenes, including methyl eugenol and the known carcinogen safrole, score negative in the Salmonella assay but score positive in the yeast DEL assay that selects for intrachromosomal recombination events in the yeast Saccharomyces cerevisiae. In an attempt to dissociate the beneficial properties of methyl eugenol from its genotoxic properties, saturated or fluorinated analogs were evaluated for their ability to induce intrachromosomal (DEL) recombination in yeast. Field tests have previously shown that all of the analogs used have appreciable properties as fruit fly attractants. The analogs 1,2-dimethoxy-4-ethylbenzene, 1,2-dimethoxy-4-(2-fluoro-2-propenyl)benzene, 1,2-dimethoxy-4-(2-fluoroethyl)benzene and 1,2-dimethoxy-4-(3-fluoro-2-propenyl)benzene all showed reduced toxicity and reduced recombinagenicity in yeast compared to methyl eugenol. These results confirm the validity of fluorination and/or removal of the 2-propenyl moiety in reducing the toxicity and recombinagenicity of methyl eugenol derivatives.

Ring-Fluorinated Analog of Methyl Eugenol: Attractiveness to and Metabolism in the Oriental Fruit Fly, Bactrocera Dorsalis (Hendel)

Oriental fruit fly, Bactrocera dorsalis (Hendel), males are highly attracted to the natural phenylpropanoid methyl eugenol (ME). They compulsively feed on ME and metabolize it to ring and side-chain hydroxylated compounds that have both pheromonal and allomonal functions. Side-chain metabolic activation of ME leading to (E)-coniferyl alcohol has long been recognized as a primary reason for hepatocarcinogenicity of this compound in rodents. Earlier, we demonstrated that introduction of a fluorine atom at the terminal carbon of the ME side chain significantly depressed metabolism and specifically reduced formation of coniferyl alcohol but had little effect on field attractiveness to B. dorsalis. In the current paper, we demonstrate that fluorination of ME at the 4 position of the aromatic ring blocks metabolic ring-hydroxylation but overall enhances side-chain metabolism by increasing production of fluorinated (E)-coniferyl alcohol. In laboratory experiments, oriental fruit fly males were attracted to and readily consumed 1,2-dimethoxy-4-fluoro-5-(2-propenyl)benzene (I) at rates similar to ME but metabolized it faster. Flies that consumed the fluorine analog were as healthy post feeding as ones fed on methyl eugenol. In field trials, the fluorine analog I was ∼50% less attractive to male B. dorsalis than ME.

Monofluoro analogues of methyl eugenol: new attractants for males of Bactrocera dorsalis (Hendel) (Dipt., Tephritidae)1

Abstract: Reports questioning the safety of methyl eugenol (1,2‐dimethoxy‐4‐[2‐propenyl] benzene) stimulated us to develop and test synthetic analogues that may be used as alternative attractants for oriental fruit fly, Bactrocera dorsalis (Hendel), males. Attraction to one propyl‐substituted and six monofluorine‐substituted methyl eugenol analogues were compared with attraction to methyl eugenol in field bioassays with both laboratory‐reared and wild oriental fruit fly males. The attractiveness of the test compounds to oriental fruit fly males was compared using two parameters: number of adults caught per trap and number of adults caught per mg of compounds released in traps. Based on these two parameters (E)‐1,2‐dimethoxy‐4‐(3‐fiuoro‐2‐propenyl)benzene was consistently as attractive as methyl eugenol to both laboratory‐reared and wild oriental fruit fly males. With further studies to determine optimum release rates, (E)‐1,2‐dimethoxy‐4‐(3‐fluoro‐2‐propenyl)benzene may potentially replace methyl eugenol for survey, detection, delimitation of infestation and eradication of oriental fruit fly populations.

Assessment of Navel Oranges, Clementine Tangerines, and Rutaceous Fruits as Hosts of Bactrocera cucurbitae and Bactrocera latifrons (Diptera: Tephritidae).

Export of Citrus spp. fruits may require risk mitigation measures if grown in areas with established tephritid fruit fly (Diptera: Tephritidae) populations capable of infesting the fruits. The host status of Citrus spp. fruits is unclear for two tephritid fruit fly species whose geographic ranges have expanded in recent years: melon fly, Bactrocera cucurbitae (Cocquillett), and Bactrocera latifrons (Hendel). In no choice cage infestation studies, B. latifrons oviposited into intact and punctured Washington navel oranges (Citrus sinensis [L.] Osbeck) and Clementine tangerines (C. reticulata L. var. Clementine), but eggs rarely developed to the adult stage. B. cucurbitae readily infested intact and punctured tangerines, and to a lesser extent punctured oranges, but did not infest intact oranges. Limited cage infestation and only a single literature report of field Citrus spp. infestation suggest that risk mitigation of Citrus spp. for B. latifrons is not needed. Risk mitigation options of Citrus spp. for B. cucurbitae, including heat and cold treatments and systems approaches, are discussed.

Natural Field Infestation of Mangifera casturi and Mangifera lalijiwa by Oriental Fruit Fly, Bactrocera dorsalis (Diptera: Tephritidae):

Mango, Mangifera indica (Anacardiaceae), is a crop cultivated pantropically. There are, however, many other Mangifera spp (“mango relatives”) which have much more restricted distributions and are poorly known but have potential to produce mango-like fruits in areas where mangoes do not grow well or could be tapped in mango breeding programs. Because of the restricted distribution of many of the Mangifera spp, there has also been limited data collected on susceptibility of their fruits to infestation by tephritid fruit flies which is important to know for concerns both for quality of production and for quarantine security of fruit exports. Here, we report on natural field infestation by the oriental fruit fly, Bactrocera dorsalis (Diptera: Tephritidae), of two mango relatives native to Indonesia: Mangifera casturi and Mangifera lalijiwa. Rates of infestation of fruits of these two Mangifera spp by tephritid fruit flies have not previously been reported.

Natural Field Infestation of and by Oriental Fruit Fly, (Diptera: Tephritidae)

Mango, Mangifera indica (Anacardiaceae), is a crop cultivated pantropically. There are, however, many other Mangifera spp (“mango relatives”) which have much more restricted distributions and are poorly known but have potential to produce mango-like fruits in areas where mangoes do not grow well or could be tapped in mango breeding programs. Because of the restricted distribution of many of the Mangifera spp, there has also been limited data collected on susceptibility of their fruits to infestation by tephritid fruit flies which is important to know for concerns both for quality of production and for quarantine security of fruit exports. Here, we report on natural field infestation by the oriental fruit fly, Bactrocera dorsalis (Diptera: Tephritidae), of two mango relatives native to Indonesia: Mangifera casturi and Mangifera lalijiwa . Rates of infestation of fruits of these two Mangifera spp by tephritid fruit flies have not previously been reported.