Quinone production of some species of Tribolium

The quinone secretions of 6 Tribolium species were analyzed qualitatively and quantitatively by gas chromatography. Procedures were developed for collecting and weighing the secretion which prevented its contamination and oxidation of the quinones. Secretions of all species contained 2-methyl- and 2-ethyl-1,4-benzoquinones in amounts ranging from 50.5% in T. brevicornis to 73% in T. confusum. Ratios of 2-methyl- to 2-ethyl-1,4-benzoquinone were 1:1.7 in 2 species and 1:2.6 to 1:2.7 in 4 species. The most prevalent non-quinone in secretions of all species was 1-pentadecene, varying from 15.6% in T. confusum to 19.9% in T. brevicornis. Three unidentified compounds, probably long-chain hydrocarbons, were found and designated biosolvents. BS-2 was present in secretions of all species, BS-1a in 4 species and traces of BS-1b in 2 species. The primary function of 1-pentadecene, and probably the unidentified biosolvents, is quinone solvency. This is discussed in relation to other previously proposed functions and to the recently discovered activity as a sex pheromone.     

An arthropod deterrent attracts specialised bees to their host plants

Many bee species are adapted to just a few specific plants in order to collect pollen (oligolecty). To reproduce successfully, it is important for oligolectic bees to find and recognise the specific host flowers. In this study, we investigated the role of floral volatiles used by an oligolectic bee to recognise its host plants. We compared the attractiveness of natural and synthetic scent samples of host flowers to foraging-naïve and -experienced Hoplitis adunca (Megachilidae) bees that are specialised on Echium and Pontechium (Boraginaceae) plants. The investigations showed that naïve H. adunca females are attracted to 1,4-benzoquinone. During their lifetime, bees learn additional floral cues while foraging on host flowers. In contrast to naïve ones, experienced H. adunca females use, in addition to 1,4-benzoquinone, other compounds to recognise their host plants. 1,4-Benzoquinone is an uncommon floral compound only known from the host plants of H. adunca, and is therefore ideally suited to be used as a plant-specific recognition cue. Several arthropods use this compound to deter insect predators. Therefore, 1,4-benzoquinone as an attractant in Echium flowers may have evolved from a primary function as a defensive compound against insect herbivores.     

European earwig (Forficula auricularia) as a novel host for the entomopathogenic nematode Steinernema carpocapsae

The natural history of many entomopathogenic nematode species remains unknown, despite their wide commercial availability as biological control agents. The ambushing entomopathogenic nematode, Steinernema carpocapsae, and the introduced European earwig, Forficula auricularia, forage on the soil surface. Since they likely encounter one another in nature, we hypothesized that earwigs are susceptible to nematode infection. In the laboratory, the LC₅₀ for F. auricularia was 226 S. carpocapsae/earwig and the reproductive potential was 123.5 infective juvenile nematodes/mg tissue. This susceptibility depended on host body size with significantly higher mortality rates seen in larger earwigs. In a study of host recognition behavior, S. carpocapsae infective juveniles responded to earwig cuticle as strongly as they did to Galleria mellonella cuticle. We also found that earwigs exposed to S. carpocapsae cleaned and scratched their front, middle and back legs significantly more than controls. Coupled with previous field data, these findings lead us to suggest that F. auricularia may be a potential host for S. carpocapsae.     

Compatibility between Forficula auricularia and entomopathogenic nematodes to be used in pome fruit pest management

Use of predators, parasitoids and entomopathogens as biocontrol agents in pome fruit production can lead to more efficient and sustainable pest management programmes. The European earwig (Forficula auricularia Linnaeus [Dermaptera: Forficulidae]) is a major predator of key pests in pome fruit orchards, and entomopathogenic nematodes (EPNs) of the families Steinernematidae and Heterorhabditidae are obligate parasites of a large number of insect species. Therefore, the interaction between earwigs and EPNs can play an important role in pest management programmes. Susceptibility of the European earwig to Steinernema carpocapsae, Steinernema feltiae (Steinernematidae) and Heterorhabditis bacteriophora (Heterorhabditidae) was evaluated. S. carpocapsae was the only tested EPN capable of killing the European earwig. However, the European earwig can detect the presence of S. carpocapsae and therefore avoid nematode‐treated shelters. An earwig deterrent activity in EPN‐killed codling moth larvae that reduces the foraging of European earwig on insect cadavers containing nematodes and allows nematodes to complete their life cycle was also assessed with the three species of nematodes. These findings suggest a positive compatibility between the European earwig and EPNs.     

Necromenic life style of Histiostoma polypori (Acari: Histiostomatidae)

Histiostoma polypori (Histiostomatidae, Astigmata) is associated with the earwig Forficula auricularia, which has an interesting brood behavior: the adult earwig female cares for her eggs and stays with the N2 and N3 nymphs in the nest. Deutonymphs of H. polypori only leave the female earwig to develop on dead earwig N2 and N3 nymphs. The newly molted deutonymphs attach to live earwig N3 nymphs. The earwig’s cleaning behavior displaces the deutonymphs to the exuvial suture, around the area between cephalon and prothorax. From there, deutonymphs switch from one earwig stage to the following, always occupying that region. Histiostoma polypori obviously has a necromenic life style, that is, it ascends a carrier organism and develops on the carrier’s cadavers. Necromeny within the Histiostomatidae presumably derived at least twice convergently from phoretic transport.     

Vertical distribution of earwigs (Dermaptera: Forficulidae) in a temperate lowland forest,based on sampling with a mobile aerial lift platform

Although earwigs (Dermaptera) may be important components of ecosystems because of their locally high abundance and omnivory, their vertical distribution among forest strata is poorly understood. This study used a mobile aerial lift platform to survey the spatiotemporal distribution of earwigs along the vertical dimension in a forest. In 2013 and 2014, 57 trees in a lowland floodplain forest were sampled in the southeastern Czech Republic, Central Europe. Earwigs were collected along the complete vertical gradient of the foliage of the trees using square beating sheets and exhaustors. Of the three recorded earwig species (Apterygida media, Chelidura acanthopygia and Forficula auricularia), A. media was the most abundant. The distribution of its abundance with the height from ground (in the tree leaf layer) was unimodal, with a peak at 4–10 m, indicating that A. media is arboricolous. The vertical stratification of A. media differed among developmental stages, and in its abundance among tree species. Investigation of insect vertical stratification in forests should be facilitated by the use of a mobile aerial lift platform.     

Abundance,interannual variation and potential pest predator role of two co‐occurring earwig species in citrus canopies

Earwigs are usually considered pest predators in orchards. Because of its worldwide distribution, most research on earwigs focuses on the European earwig Forficula auricularia Linnaeus (Insecta: Dermaptera: Forficulidae). However, very little is known of this species in Mediterranean citrus orchards. Earwigs and aphids were collected monthly during 5 years (2006–2010) from citrus canopies. Two species of earwigs were found: F. auricularia and Forficula pubescens Gené (=Guanchia pubescens), with the latter seldom cited in the literature. The goals of this study were (i) to document the abundance of these two earwig species in Mediterranean citrus canopies; (ii) to determine whether they are positively or negatively associated with each other, or randomly distributed; (iii) to measure the interannual variation of the abundance of both species during a 5‐year period and (iv) to evaluate the potential role of earwigs as pest predators in citrus canopies. As compared to colder regions, F. auricularia active period in citrus canopies in our study site lasted longer. Both species co‐occurred randomly in canopies. In 2006, both species showed approximately the same abundance, but in 2010, F. pubescens abundance in canopies was 28 times greater than that of F. auricularia. The potential role of earwigs as pest predators is higher in the Mediterranean than in other colder regions, because of the longer active period. F. auricularia is a sedentary generalist predator, already present in citrus canopies at the onset of most pest outbreaks, while F. pubescens arrived later to the canopies, but most likely was abundant enough to contribute in the control of citrus pests.     

The synthesis and evaluation of thymoquinone analogues as anti-ovarian cancer and antimalarial agents

Thymoquinone (TQ), 2-isopropyl-5-methyl-1,4-benzoquinone, a natural product isolated from Nigella sativa L., has previously been demonstrated to exhibit antiproliferative activity in vitro against a range of cancers as well as the human malarial parasite Plasmodium falciparum. We describe here the synthesis of a series of analogues of TQ that explore the potential for nitrogen-substitution to this scaffold, or reduction to a hydroquinone scaffold, in increasing the potency of this antiproliferative activity against ovarian cancer cell lines and P. falciparum. In addition, alkyl or halogen-substituted analogues were commercially sourced and tested in parallel. Several TQ analogues with improved potency against ovarian cancer cells and P. falciparum were found, although this increase is suggested to be moderate. Key aspects of the structure activity relationship that could be further explored are highlighted.     

欧洲球螋的检疫

北京出入境检验检疫局从美国进境旅客携带的石榴中检出欧洲球螋。了解欧洲球螋的基本特性,能为相关部门对其检疫鉴定提供参考依据。对欧洲球螋的相关文献进行了查阅和整理,详细介绍了欧洲球螋的分类地位、分布、形态特征及近似种等信息,我国出入境检验检疫部门对球螋属的截获情况,讨论了欧洲球螋的检疫意义。认为欧洲球螋在我国无分布且具有一定的入侵风险,口岸应对该虫引起足够的重视。     

Insecticidal activities of a Diospyros kaki root-isolated constituent and its derivatives against Nilaparvata lugens and Laodelphax striatellus

Diospyros kaki root-derived materials were examined for insecticidal properties against Nilaparvata lugens and Laodelphax striatellus. Based on the LD₅₀ values, the chloroform fraction of D. kaki extracts showed the most activity against N. lugens (3.78 μg/female) and L. striatellus (7.32 μg/female). The active constituent of the chloroform fraction was isolated by various chromatographic methods and was identified as 5-hydroxy-2-methyl-1,4-naphthoquinone by spectroscopic analyses. To establish the structure–activity relationships, the insecticidal effects of 5-hydroxy-2-methyl-1,4-naphthoquinone and its derivatives against N. lugens and L. striatellus were determined using micro-topical application bioassays. On the basis of LD₅₀ values, 5-hydroxy-1,4-naphthoquinone was the most effective against N. lugens (0.072 μg/female) and L. striatellus (0.183 μg/female). 2-Bromo-1,4-naphthoquinone, 2-hydroxy-1,4-naphthoquinone, and 5-hydroxy-2-methyl-1,4-naphthoquinone also had potent insecticidal activities against N. lugens and L. striatellus. In contrast, no insecticidal activity was observed with 2-methoxy-1,4-naphthoquinone or 2-methyl-1,4-naphthoquinone. These results indicate that the functional group (bromo- and hydroxyl-) at the C-2 position of the 1,4-naphthoquinone skeleton and the change in position of the hydroxyl group play important roles in insecticidal activity. Therefore, naturally occurring D. kaki root-derived 5-hydroxy-2-methyl-1,4-naphthoquinone and its derivatives may be suitable as insecticides.     

Interaction of electron acceptors with thylakoids from halophytic and non-halophytic species

Thylakoid membranes isolated from halophytic species showed differences in their interactions with ionic and lipophilic electron acceptors when compared to thylakoids from non-halophytes. FeCN was considerably less efficient as electron acceptor with halophyte thylakoids, supporting much lower rates of O₂ evolution and having a lower affinity. FeCN accepted electrons at a different, DMMIB insensitive, site with these thylakoids. 1,4-Benzo-quinones with less positive midpoint potentials were less effective in accepting electrons from halophyte thylakoids compared to nonhalophyte thylakoids, also reflected in lower rates of O₂ evolution and lower affinity. Considering the lipolphilic nature and the fact that there was no apparent change in the site donating electrons to the quinones, an alteration in the midpoint potential of this site by about +100mV is postulated for the halophyte thylakoids.Abbreviations AMPD 2-amino-2-methyl-1,3-propanediol - Cyt b₆/f cytochrome b₆/f complex - DBMIB 2,5-dibromo-6-isopropyl-3-methyl-1,4-benzoquinone - DCBQ 2,6-dichloro-1,4-benzoquinone - DCIP 2,6-dichlorophenol-indolphenol - DMBQ 2,5-dimethyl-1,4-benzoquinone - E_m7 midpoint redox potential at pH 7.0, FeCN-K₃Fe(CN)₆ - HNQ 5-hydroxy-1,4-naphthoquinone - MV methylviologen - NQ 1,4-naphthoquinone - PBQ phenyl-1,4-benzoquinone - PC plastocyanin - PQ plastoquinone     

Predictive thresholds for forecasting the compatibility of <Emphasis Type="Italic">Forficula auricularia</Emphasis> and <Emphasis Type="Italic">Aphelinus mali</Emphasis> as biological control agents against woolly apple aphid in apple orchards

The woolly apple aphid (WAA), Eriosoma lanigerum (Hausmann) (Hemiptera: Aphididae) is a well-known pest of apple orchards world-wide. Several studies have demonstrated variable control of WAA populations by the European earwig, Forficula auricularia (L.) (Dermaptera: Forficulidae) and the WAA parasitoid Aphelinus mali (Halderman) (Hymenoptera: Aphelinidae). We examine whether a beneficial interaction between F. auricularia and A. mali exists and calculate optimal numbers for each species to maintain WAA infestations below acceptable levels. We demonstrate that trees possessing >14 earwigs per trunk trap per week within the first seven weeks post-blossom contained WAA infestations well below acceptable levels. Where these earwig thresholds were not met, a first generation of A.mali greater than 0.5 wasps per tree was required. If these beneficial insect targets were not met, severe WAA infestations occurred. Our findings suggest that if F. auricularia and A. mali numbers exceed these thresholds chemical intervention may not be required.     

Study of the protein-ubiquinone interaction in succinate-cytochrome C reductase with azido-ubiquinone derivatives

Several azido-ubiquinones have been synthesized for the study of protein-ubiquinone interaction in succinate-cytochrome $\text{c}$ reductase. In the absence of light, azido-ubiquinones are partially effective in restoring enzymatic activity to ubiquinone- and phospholipid-depleted reductase and the binding of azido-ubiquinones can be partially reversed by 5-(10-bromodecyl)-ubiquinone. When 2-azido-3-methoxy-5-geranyl-6-methyl-1,4-benzoquinone reactivated reductase is illuminated with long wavelength UV light, a complete and irreversible inhibition is observed. This specific photo-inactivation, exerted only by 2-azido-3-methoxy-5-geranyl-6-methyl-1,4-benzoquinone, and not by other azido-ubiquinone derivatives, is evidence for the existence of a specific benzoquinone ring binding site in the enzyme.     

Biosynthesis of tocopherols: A re-examination of the biosynthesis and metabolism of 2-methyl-6-phytyl-1,4-benzoquinol

A number of previous studies of the involvement of 2-methyl-6-phytyl-1,4-benzoquinol in the biosynthesis of α-tocopherol have failed to take account of the fact that this quinol and its quinone have very similar chromatographic properties to those of 2-methyl-3-phytyl-1,4-benzoquinol and 2-methyl-3-phytyl-1,4-benzoquinone respectively. It has now been shown that the two quinones can be separated from each other either by multidevelopment TLC or by HPLC and that the claims made earlier with regard to the biosynthesis and metabolism of 2-methyl-6-phytyl-1,4-benzoquinol in chloroplasts are correct. In particular, it has been established that this quinol is the only methyl phytylbenzoquinol formed from homogentisate and phytyl pyrophosphate in chloroplast preparations. It has also been shown for the first time that lettuce chloroplasts are able to synthesize ³H-labelled α- and γ-tocopherols from [methylene-³H] homogentisate.     

Aerobic respiration in mutants of Escherichia coli accumulating quinone analogues of ubiquinone

The ability of three naturally occurring analogues of ubiquinone to function in aerobic respiration in Escherichia coli has been studied. The compounds, which differ from ubiquinone in terms of the substituents on the quinone ring, accumulate in the cytoplasmic membranes of ubiE^?, ubiF^? and ubiG^? mutants. One of the analogues (2-octaprenyl-3-methyl-6-methoxy-1,4-benzoquinone, MMQ), which lacks the 5-methoxyl group of the benzoquinone ring of ubiquinone promoted the oxidation of NADH, d-lactate and α-glycerophosphate but not succinate. Electron transport supported by MMQ was found to be coupled to phosphorylation. In contrast, 2-octaprenyl-6-methoxy-1,4-benzoquinone, which lacks both the 3-methyl and 5-methoxyl groups of ubiquinone, and 2-octaprenyl-3-methyl-5-hydroxy-6-methoxy-1,4-benzoquinone, in which the 5-methoxyl group of ubiquinone is replaced by an hydroxyl group, were virtually inactive in the oxidases tested. The ability of MMQ to function in respiration in isolated membranes is consistent with the findings that the growth rate and yield of a ubiF^? strain, unlike other ubi^? strains, were only slightly lower than those of a ubiF⁺ strain.The fact that MMQ is active in some but not all oxidases provides further support for the concept that the quinones link the individual dehydrogenases to the respiratory chain and that each dehydrogenase has specific structural requirements for quinone acceptors.     

A quinone-hydroquinone couple from the Brown alga Cystoseira stricta

2′E,6′E)-2-(10′,11′-Dihydroxygeranylgeranyl)-6-methylquinol and 2′E,6′E)-2(10′,11′-dihydroxyeranylgeranyl)-6-methyl-1,4-benzoquinone have been isolated from the brown alga Cystoseira stricta. The structures of the new algal metabolites have been elucidated by spectral analysis and chemical degradation.     

Site-specific isotope labeling demonstrates a large mesomeric resonance effect of the methoxy groups on the carbonyl frequency in ubiquinones

The splitting of the carbonyl infrared bands of 2-methoxy-1,4-benzoquinone in solution can be related to a mesomeric resonance phenomenon leading to a conformation of the O-CH₃ bond coplanar to the quinone ring. The delocalization of the electron density induces a frequency downshift of the C₄=O carbonyl compared to 1,4-benzoquinone. This in turns decouples the two carbonyls leading to an upshift of the C₁=O vibration. Using selective ¹³C-labeling of Q₀ (2,3-dimethoxy-5-methyl-1,4-benzoquinone), we show that the effect of mesomeric resonance is an essential determinant of the carbonyl frequencies of ubiquinone in solution.     

Synthesis and biological evaluation of a series of A,B-ring modified 16,17-secoandrostane derivatives

The starting compound for the synthesis of 16,17-secoandrostane derivatives with the 4-en-3-on, 1,4-dien-3-on, 4,6-dien-3-on, and 1,4,6-trien-3-on systems was 3β-hydroxy-17-methyl-16,17-secoandrost-5-en-16-nitrile-17-one (1), the Oppenauer oxidation of which yielded the corresponding 4-en-3-one derivative 2. Dehydrogenation of compound 2 with the aid of 2,3,5,6-tetrachloro-1,4-benzoquinone (chloranil) gave the three products: 17-methyl-16,17-secoandrosta-1,4-dien-3,17-dione-16-nitrile (3), 17-methyl-16,17-secoandrosta-4,6-dien-3,17-dione-16-nitrile (4), and 17-methyl-16,17-secoandrosta-1,4,6-trien-3,17-dione-16-nitrile (5). On the other hand, epoxidation of compound 2 resulted in a mixture of α and β isomers of 4,5-epoxy-17-methyl-16,17-secoandrosta-3,17-dione-16-nitrile (6 and 7). Opening of the oxirane rings of the mixture of 6 and 7 by the action of formic acid yielded the 4-hydroxy-4-en derivative 8. Antiaromatase activity and in vitro cytotoxicity against three tumor cell lines (human breast adenocarcinoma ER+, MCF-7, human breast adenocarcinoma ER−, MDA-MB-231, and prostate cancer PC3) of selected compounds were evaluated. Compound 2 exhibited a relatively strong inhibition of aromatase and extremely potent cytotoxicity against PC3 cells. Compound 8 showed satisfactory cytotoxicity against MCF-7 cells.     

Furanosesquiterpenoids of Commiphora erythraea and C. myrrh

The isolation and structure determination of two new furanosesquiterpenoids, 2-O-acetyl-8,12-epoxygermacra-1(10),4,7,11-tetraene and 2-O-methyl-8,12-epoxygermacra-1(10)-4,7,11-tetraene, from gum exudates of Commiphora myrrh are reported. These two compounds, together with the known furanodienone isolated from C. erythraea, were found to have ixodicidal activity against Rhipicephalus appendiculatus tick larvae.