Chemical Defense in Millipedes (Myriapoda,Diplopoda): Do Representatives of the Family Blaniulidae Belong to the ‘Quinone’ Clade?

The defensive secretions of two blaniulid millipedes, Nopoiulus kochii and Cibiniulus phlepsii, were characterized by GC‐FID and GC/MS analyses, which showed the presence of a complex mixture of benzoquinones, hydroquinones, and oleates. Altogether, 13 compounds were identified. The major compound in the secretions of both analyzed species was 2‐methyl‐1,4‐benzoquinone (toluquinone). The second major constituent in the N. kochii secretion was 2‐methyl‐3,4‐(methylenedioxy)phenol, while in that of C. phlepsii, it was 2‐methoxy‐3‐methyl‐1,4‐benzoquinone. The defensive secretion of N. kochii also showed a high content of hydroquinones (13.5%) in comparison to that of C. phlepsii (0.8%). Hexyl oleate and octyl oleate were detected for the first time in defensive millipede fluids. The chemical composition of the defensive secretions supports the chemotaxonomic position of the family Blaniulidae in the ‘quinone’ millipede clade.     

Unusual structural and chemical characteristics of the Dufour gland in the ant Meranoplus diversus

Abstract The Dufour gland of both queens and workers of Meranoplus diversus is very large. The reservoir is lined with flat epithelial cells, which usually contain smooth endoplasmic reticulum but also show the unusual accumulation of electron‐dense inclusions. Chemically, the gland contains an unusual mixture of long‐chain fatty acids and their derivatives, including hydrocarbons, ketones and amines with long‐chain substituents, hydroquinone, and sugars. Some of the substances identified are already known as insect defensive compounds against other arthropods.     

Secolignans with antiangiogenic activities from Peperomia dindygulensis

Two new secolignans, peperomins G and H ( 1 and 2 , resp.), were isolated from the whole plant of Peperomia dindygulensis, together with five known secolignans, peperomin A ( 3 ), peperomin E ( 4 ), peperomin B ( 5 ), 2,3‐trans‐2‐methyl‐3‐{(3‐hydroxy‐4,5‐dimethoxyphenyl)[5‐methoxy‐3,4‐(methylenedioxy)phenyl]methyl}butyrolactone ( 6 ), 2,3‐cis‐2‐(hydroxymethyl)‐3‐{bis[5‐methoxy‐3,4‐(methylenedioxy)phenyl]methyl}butyrolactone ( 7 ). Their structures and configurations were elucidated by spectroscopic methods including 2D‐NMR techniques. Antiangiogenic effects of all compounds were evaluated using human umbilical vein endothelial cells (HUVEC) proliferation and tube‐formation tests, with compounds 4 and 5 being active in the bioassay. Compounds 4 and 5 induced obvious cell toxicity to HUVEC with IC₅₀ values of 1.64±0.19 and 8.44±0.4 μM , respectively. Compounds 4 and 5 also exhibited significant HUVEC tube formation‐inhibiting activity with IC₅₀ values of 3.13±0.09 and 6.24±0.12 μM , respectively.     

A comparative study of the chemical defensive system of tenebrionid beetles: Chemistry of the secretions

The chemical compositions of the defensive secretions of 147 species of tenebrionid beetles from 55 genera and 16 tribes were analysed by gas-liquid chromatography on three different stationary phases. All species contained toluquinone and ethylquinone, but benzoquinone was relatively rare. A great many species contained various 1-alkenes in addition to quinones. Species of Pedinini were distinguished by the secretion of n-propylquinone, whereas 2,3-methylmethoxyquinone set apart the subgenus Blapylis (of Eleodes) and possibly Amphidora. Large amounts of octanoic acid were restricted to the genera Embaphion and Neobaphion (both Eleodini), and small amounts of 1-nonadecene were restricted to Lariversius (Eleodini) and Cratidus (Amphidorini). Most species of Eleodes had complex secretions with toluquinone, ethylquinone, 1-nonene, 1-undecene, and 1-tridecene in various ratios. 1-Pentadecene and/or 1-heptadene occurred in substantial amounts in Tribolium, Uloma, Phaleria, Pyanisia, Melanopterus, Gonopus, Schelodontes, Psorodes, Neatus, and Merinus. The genus Argoporis (Scaurini) is unique in its synthesis of 6-alkyl-1,4-naphthoquinones, and other members of the tribe also contain characteristic, as yet unidentified compounds. Many groups not distinguished by unique compounds still show characteristic combinations and ratios of compounds, and these are discussed along with problems of variation at the individual, geographic, specific, and generic levels.     

Wehrsubstanzen und wehrverhalten der termite Macrotermes carbonarius

Soldiers of the termite Macrotermes carbonarius which forage on the surface have a special defensive behaviour: they stab their sickle-shaped mandibles into the skin of the enemy and by crossing them they are irreversibly fixed. After this a brownish watery secretion from the huge labial glands is discharged by rhythmic contractions of the abdomen. The secretion was analysed by thin-layer chromatography and u.v.-spectroscopy. The main compound is toluquinone. A minor component is benzoquinone,     

Inhibition of glucose transport by benzoquinone and the addition product of benzoquinone and dithiothreitol

Hydroxylated benzene derivatives inhibited transport of d-glucose into calf-thymocyte plasma-membrane vesicles. The relative effectiveness of these was pyrogallol >hydroquinone catechol phloroglucinol. The most thoroughly studied of these agents, hydroquinone, produced weak, immediate inhibition when first added to membranes (K_i > 10 mM). This was followed by a gradual, time-dependent inhibition of the residual transport activity. The instantaneous inhibition could not be prevented by any agent tested, whereas the time-dependent phase was affected by reducing agents and superoxide dismutase. Several reducing agents (dithiothreitol, glutathione, NADH, ascorbate, bisulfite but not cysteine) prevented, while superoxide dismutase and cysteine potentiated time-dependent inhibition when added to the membrane suspension simultaneously with hydroquinone. NADH and ascorbate also prevented, whereas dithiothreitol potentiated, further time-dependent inhibition when added to membranes 2 h after hydroquinone. In contrast, all three reducing agents arrested time-dependent inhibition when added 2 h after pyrogallol. Numerous agents had no effect on time-dependent hydroquinone inhibition: oxidants (H₂O₂), metal chelators (EDTA, bathophenanthroline disulfonate, Desferral), radical scavengers (benzoate, ethanol), anti-oxidants (butylated hydroxytoluene) and catalase. Benzoquinone, an oxidation product of hydroquinone, was a much more potent inhibitor (K_i 1 mM) than hydroquinone. Several reducing agents (ascorbate, NADH, bisulfite) prevented this effect, while cysteine and dithiothreitol potentiated it. Below 300 μM, benzoquinone had little or no effect on sugar transport with or without glutathione or cysteine. Addition of dithiothreitol to benzoquinone (10–300 μM) resulted in potent inhibition of sugar transport (K_i 50 μM). Maximal inhibition occurred with a 1 : 1 mol ratio of these agents or with excess dithiothreitol. The inhibitory agent from benzoquinone and dithiothreitol lost potency in the presence of air and membranes, but was stable for hours in the presence of either of these alone. dl-threo-1,4-bis(2,5-dihydroxyphenylthio)-2,3-butanediol was obtained from the reaction of equimolar quantities of dithiothreitol and benzoquinone in ethanol. The structure of this adduct was established by spectroscopic and chemical methods. This compound exhibited all of the properties of the inhibitor which had been formed from benzoquinone and dithiothreitol in aqueous solution.     

Detrimental effects of plant compounds on a polyembryonic parasitoid are mediated through its highly polyphagous herbivore host

Plant defensive compounds can have sometimes severe deleterious effects on both herbivores and their natural enemies. Iridoid glycosides (IGs) are defensive compounds that are well established as deterrent to several generalist herbivores and generalist predators. Trichoplusia ni Hübner (Lepidoptera: Noctuidae) is exceptional among generalist herbivores for its ability to tolerate and thrive when feeding upon IG‐producing plant species; however, it is not known whether the compounds themselves have a harmful effect on T. ni and whether the effects in turn affect its oligophagous endoparasitoid Copidosoma floridanum Ashmead (Hymenoptera: Encyrtidae). To examine these effects, a semi‐purified extract of the IG‐containing plant Plantago lanceolata L. (Plantaginaceae), containing the IGs aucubin and catalpol, was added to artificial diets at 0, 1, 5, or 10% diet dry weight. These diets were fed to both C. floridanum‐parasitized and unparasitized T. ni. Diets higher in IGs tended to be more toxic to both parasitized and unparasitized larvae: host larvae that did survive were slightly smaller and took longer to develop on higher IG diets and total clutch size and survival of the parasitoid C. floridanum were greatly reduced as the host's dietary intake of IGs increased. Only small amounts of aucubin were detected inside the T. ni hemocoel, suggesting that the negative effect of these compounds on C. floridanum is due to nutritional quality of the host being reduced rather than direct toxic effects of the compounds.     

A one‐pot process for synthesis of mitomycin analogs catalyzed by laccase/lipase optimized by response surface methodology

To reach the excellent yield as well as environmental friendliness, an efficient one‐pot process for the synthesis of 2‐methyl‐3‐n‐butylaminoyl‐1,4‐benzoquinone, a mitomycin‐like compound by the domino reaction of 2‐methyl‐1,4‐hydroquinone and butylamine using laccase/lipase as co‐catalysts, has been developed. In this present study, the process proposed here was further improved by optimizing the relevant factors using the response surface methodology based on Box–Benkhen Design. The optimum condition that afforded the highest yield (98%) of 2‐methyl‐3‐n‐butylaminoyl‐1,4‐benzoquinone was obtained as follows: molar ratio of amines to hydroquinones 1.16:1, activity ratio of laccase to lipase 1.14:2, and reaction temperature 38.9°C. The results obtained indicate that this process may be useful as a green alternative method for higher yield production of mitomycin analogs.     

Exploring a key synapomorphy: correlations between structure and function in the sternum V glands of Trichoptera and Lepidoptera (Insecta)

The sternum V glands are a key synapomorphy that unites Trichoptera with Lepidoptera, but their functional aspects have not been analysed from an evolutionary perspective. We examine phylogenetic trends and correlations between chemical and morphological features of these glands. The most likely ancestral gland compounds are heptan‐2‐ol, 4‐hepten‐2‐one and ‐ol, nonan‐2‐one, and 6‐nonen‐2‐one and ‐ol, making pheromone production a plausible ancestral function. The most widespread gland compounds (heptan‐2‐one and ‐ol and nonan‐2‐one and ‐ol) are not known from Apataniidae + Limnephilidae (Trichoptera), which in turn uniquely produce a number of methylated 3‐ketones and their corresponding alcohols, probably functioning as pheromones. We propose a functional connection between perforated patches on sternum IV in females and a scaly/dome‐covered area around the gland openings, as well as between perforated patches and lack of Trichoptera‐type opening muscles. We also propose a functional connection between the shape of the gland reservoirs and the presence of gland reservoir musculature. The perforated patches were significantly correlated with several gland compounds that had double bonds between carbon atoms: the double bonds may lower the viscosity of the compounds, facilitating secretion through the tiny pores of the perforated patches. The production of defensive substances in Pycnopsyche (Trichoptera: Limnephilidae) is probably connected to the presence of large, compartmentalized gland reservoirs. Large glands in male Hydropsyche (Trichoptera: Hydropsychidae) are probably linked to male aggregation pheromone production. The relative sizes of sternum V gland reservoirs and fenestral gland reservoirs in female philopotamids (Trichoptera) suggest a complementary function of the two structures. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 106 , 561–579.     

Quenching of graphene quantum dots fluorescence by alkaline phosphatase activity in the presence of hydroquinone diphosphate

In this work, a turn‐off photoluminescent sensing proof‐of‐concept based on blue luminescent graphene quantum dots (GQDs) as the fluorescent probe was developed. For that purpose, GQDs optical response was related with the catalytic enzymatic activity of alkaline phosphatase (ALP), in the presence of hydroquinone diphosphate (HQDP). The hydrolysis of HQDP by ALP generated hydroquinone (HQ). The oxidation of HQ, enzymatically produced, to p‐benzoquinone (BQ) resulted in the quenching of GQDs fluorescence (FL). Therefore, the developed luminescent sensing mechanism allowed the FL quenching with ALP activity to be related and thus quantified the concentration of ALP down to 0.5 nM of enzyme. This innovative design principle appears as a promising tool for the development of enzymatic sensors based on ALP labeling with fluorescent detection or even for direct ALP luminescent quantification in an easy, fast and sensitive manner.     

Acridone Alkaloids from Swinglea glutinosa (Rutaceae) and Their Effects on Photosynthesis

Continuing our search for herbicide models based on natural products, we investigated the action mechanisms of five alkaloids isolated from Swinglea glutinosa (Rutaceae): Citrusinine‐I ( 1 ), glycocitrine‐IV ( 2 ), 1,3,5‐trihydroxy‐10‐methyl‐ 2,8‐bis(3‐methylbut‐2‐en‐1‐yl)‐9(10H)‐acridinone ( 3 ), (2R)‐2‐tert‐butyl‐3,10‐dihydro‐4,9‐dihydroxy‐11‐methoxy‐10‐methylfuro[3,2‐b]acridin‐5(2H)‐one ( 4 ), and (3R)‐2,3,4,7‐tetrahydro‐3,5,8‐trihydroxy‐6‐methoxy‐2,2,7‐trimethyl‐12H‐pyrano[2,3‐a]acridin‐12‐one ( 5 ) on several photosynthetic activities in an attempt to find new compounds that affect photosynthesis. Through polarographic techniques, the compounds inhibited the non‐cyclic electron transport in the basal, phosphorylating, and uncoupled conditions from H₂O to methylviologen (=MV). Therefore, they act as Hill reaction inhibitors. This approach still suggested that the compounds 4 and 5 had their interaction site located at photosystem I. Studies on fluorescence of chlorophyll a suggested that acridones ( 1 – 3 ) have different modes of interaction and inhibition sites on the photosystem II electron transport chain.     

Novel Phenyl‐1‐benzoxepinols from Butcher's Broom (Rusci rhizoma)

Two novel compounds, (3S)‐2,3‐dihydro‐3‐(4‐hydroxyphenyl)‐1‐benzoxepin‐8‐ol ( 1 ; ruscozepine A) and (3S)‐2,3‐dihydro‐3‐(4‐hydroxyphenyl)‐8‐methoxy‐1‐benzoxepin‐7‐ol ( 2 ; ruscozepine B) were isolated from butcher's broom (Rusci rhizoma) together with a biosynthetically possible phenylethanoid precursor, hydroxytyrosol ( 3 ). The structures were elucidated by spectroscopic methods such as 1D‐ and 2D‐NMR (COSY, HSQC, HMBC, ROESY), and HR‐EI‐MS experiments. The absolute configuration of the ruscozepines was determined by electronic circular dichroism.     

Antifouling substances of natural origin: Activity of benzoquinone compounds from Maesa Lanceolata against marine crustaceans

A screening of antifouling activity from plants extracts led to selection and further study of Maesa lanceolata Forssk. Two p‐benzoquinone compounds were isolated from the fruits and found to be active against Artemia salina. The anti‐crustacean activity of both p‐benzoquinones is reported for the first time.     

Structural characterization of 2,6‐dichloro‐p‐hydroquinone 1,2‐dioxygenase (PcpA) from Sphingobium chlorophenolicum,a new type of aromatic ring‐cleavage enzyme

PcpA (2,6‐dichloro‐p‐hydroquinone 1,2‐dioxygenase) from Sphingobium chlorophenolicum, a non‐haem Fe(II) dioxygenase capable of cleaving the aromatic ring of p‐hydroquinone and its substituted variants, is a member of the recently discovered p‐hydroquinone 1,2‐dioxygenases. Here we report the 2.6 Å structure of PcpA, which consists of four βαβββ motifs, a hallmark of the vicinal oxygen chelate superfamily. The secondary co‐ordination sphere of the Fe(II) centre forms an extensive hydrogen‐bonding network with three solvent exposed residues, linking the catalytic Fe(II) to solvent. A tight hydrophobic pocket provides p‐hydroquinones access to the Fe(II) centre. The p‐hydroxyl group is essential for the substrate‐binding, thus phenols and catechols, lacking a p‐hydroxyl group, do not bind to PcpA. Site‐directed mutagenesis and kinetic analysis confirm the critical catalytic role played by the highly conserved His10, Thr13, His226 and Arg259. Based on these results, we propose a general reaction mechanism for p‐hydroquinone 1,2‐dioxygenases.     

Carbon dioxide‐ and temperature‐mediated changes in plant defensive compounds alter food utilization of herbivores

Although the impact of elevated carbon dioxide and rising temperature on plants and animals has been extensively documented recently, only limited understanding exists regarding their combined effects. The objective of this research was to address the consequences of using combinations of elevated CO₂ and elevated temperature on a plant's defensive chemistry, and subsequent utilization of the plant as insect food. Our results indicated that elevated CO₂ and increased temperature, for the most part, act independently on the production of defensive compounds in broccoli leaves (Brassica oleracea L. var. italica). CO₂ concentrations had significant effects on the foliar water content, total phenolic compounds, polyphenol oxidase and trypsin inhibitor concentrations. The herbivore Spodoptera litura (Fabricius; Lepidoptera: Noctuidae) responded to changes in the plant secondary chemistry, with larvae consuming more plant materials that had been exposed to elevated CO₂. The food utilization efficiencies of second‐instar larvae were more sensitive to CO₂‐treated foliage than those of the third‐ and fourth‐instar larvae. Temperature did exert a significant effect on food utilization (ECD) by the larvae. Our study will provide important information in future predictions on plant–insect interactions as a result of climate change. The study also demonstrated that since various larval stages might respond differently to climate change, this possibility needs to be considered in future forecasting and monitoring.     

Oxidation of hydroquinone, 2,3-dimethylhydroquinone and 2,3,5-trimethylhydroquinone by human myeloperoxidase

Abstract

Myeloperoxidase is very susceptible to reducing radicals because the reduction potential of the ferric/ferrous redox couple is much higher compared with other peroxidases. Semiquinone radicals are known to reduce heme proteins. Therefore, the kinetics and spectra of the reactions of p-hydroquinone, 2,3-dimethylhydroquinone and 2,3,5-trimethylhydroquinone with compounds I and II were investi-gated using both sequential-mixing stopped-flow techniques and conventional spectrophotometric measurements. At pH 7 and 15°C the rate constants for compound I reacting with p-hydroquinone, 2,3-dimethylhydroquinone and 2,3,5-trimethylhydroquinone were determined to be 5.6±0.4×10⁷ M^-1s^-1, 1.3±0.1×10⁶ M^-1s^-1 and 3.1±0.3×10⁶ M^-1s^-1, respectively. The corresponding reaction rates for compound II reduction were calculated to be 4.5±0.3×10⁶ M^-1s^-1, 1.9±0.1×10⁵ M^-1s^-1 and 4.5±0.2×10⁴ M^-1s^-1, respectively. Semiquinone radicals, produced by compounds I and II in the classical peroxidation cycle, promote compound III (oxymyeloperoxidase) formation. We could monitor formation of ferrous myeloperoxidase as well as its direct transition to compound III by addition of molecular oxygen. Formation of ferrous myeloperoxidase is shown to depend strongly on the reduction potential of the corresponding redox couple benzoquinone/semiquinone. With 2,3-dimethylhydroquinone and 2,3,5-trimethylhydroquinone as substrate, myeloperoxidase is extremely quickly trapped as compound III. These MPO-typical features could have potential in designing specific drugs which inhibit the production of hypochlorous acid and consequently attenuate inflammatory tissue damage.     

Pre-copulatory isolation in sympatric Melolontha species (Coleoptera: Scarabaeidae)

1 The two most abundant cockchafer species in Europe, the forest cockchafer Melolontha hippocastani Fabr. and the European cockchafer Melolontha melolontha L., tend to form calamitous mass breedings with casual reports on sympatric and simultaneous occurrence. 2 Both species are known to use feeding‐induced green leaf volatiles (GLV) as primary attractants (sexual kairomones) for mate finding. The attractiveness of GLV is enhanced by the sex pheromones 1,4‐benzoquinone in M. hippocastani and toluquinone in M. melolontha. Phenol attracts males from both species. All three compounds are present in females of both species. 3 In the present study, it is confirmed that only male M. melolontha perform the typical swarming flight at dusk, as has already been shown for M. hippocastani. Furthermore, whether swarming Melolontha males were cross‐attracted to heterospecific females, and whether males could discriminate olfactorily between conspecific and heterospecific females, was tested in the field. 4 Males of both species preferred females when given the choice between females and males of the other species. However, they preferred conspecific females when females from both species were offered simultaneously. 5 The results suggest that species‐specific pheromone blends contribute to precopulatory reproductive isolation in sympatric populations of M. melolontha and M. hippocastani, but are not mutually exclusive or indispensable prerequisites for mate finding as in other insects.     

Enantiopurity and absolute configuration determination of arene cis‐dihydrodiol metabolites and derivatives using chiral boronic acids

The relative merits of the methods employed to determine enantiomeric excess (ee) values and absolute configurations of chiral arene and alkene cis‐1,2‐diol metabolites, including boronate formation, using racemic or enantiopure (+) and (?)‐2‐(1‐methoxyethyl)phenylboronic acid (MEPBA), are discussed. Further applications of: 1) MEPBA derived boronates of chiral mono‐ and poly‐cyclic arene cis‐dihydrodiol, cyclohex‐2‐en‐1‐one cis‐diol, heteroarene cis/trans‐2,3‐diol, and catechol metabolites in estimating their ee values, and 2) new chiral phenylboronic acids, 2‐[1‐methoxy‐2,2‐dimethylpropyl]phenyl boronic acid (MDPBA) and 2‐[1‐methoxy‐1‐phenylmethyl]phenyl boronic acid (MPPBA) and their advantages over MEPBA, as reagents for stereochemical analysis of arene and alkene cis‐diol metabolites, are presented.     

Dietary plant phenolic improves survival of bacterial infection in Manduca sexta caterpillars

Plant phenolics are generally thought to play significant roles in plant defense against herbivores and pathogens. Many plant taxa, including Solanaceae, are rich in phenolic compounds and some insect herbivores have been shown to acquire phenolics from their hosts to use them as protection against their natural enemies. Here, we demonstrate that larvae of an insect specialist on Solanaceae, the tobacco hornworm, Manduca sexta L. (Lepidoptera: Sphingidae), acquire the plant phenolic chlorogenic acid (CA), and other caffeic acid derivatives as they feed on one of their hosts, Nicotiana attenuata L. (Solanaceae), and on artificial diet supplemented with CA. We test the hypothesis that larvae fed on CA‐supplemented diet would have better resistance against bacterial infection than larvae fed on a standard CA‐free diet by injecting bacteria into the hemocoel of fourth instars. Larvae fed CA‐supplemented diet show significantly higher survival of infection with Enterococcus faecalis (Andrewes & Horder) Schleifer & Kilpper‐Bälz, but not of infection with the more virulent Pseudomonas aeruginosa (Schroeter) Migula. Larvae fed on CA‐supplemented diet possess a constitutively higher number of circulating hemocytes than larvae fed on the standard diet, but we found no other evidence of increased immune system activity, nor were larvae fed on CA‐supplemented diet better able to suppress bacterial proliferation early in the infection. Thus, our data suggest an additional defensive function of CA to the direct toxic inhibition of pathogen proliferation in the gut.     

Synthesis of novel ligustrazine derivatives as NA+/H+ exchange inhibitors

A novel series of 3,5,6‐trimethylpyrazine‐2‐methoxy (or methylamino) substituted benzoyl‐guanidine derivatives were designed and synthesized as Na⁺/H⁺ exchange (NHE) inhibitors. In this study, compounds with electron‐withdrawing substituents on the benzene ring seemed to improve NHE‐1 inhibitory activities. Compounds 6d, 6k , and 6l were found to be potent inhibitors of NHE‐1 (IC₅₀=3.0±1.6, 3.0±1.4, and 1.6±0.4 nmol/l, resp.). Furthermore, they showed a remarkable reduction of infarct size in the rat myocardial infarction model in vivo.