Floral Scent Chemistry and Pollinators of a Sexually Dimorphic Neotropical Orchid.

Catasetum is a speciose Neotropical orchid genus of which male and female flowers emit scents acting both as attractant and reward for their exclusive pollinators, male orchid bees (Euglossini: Apidae). In Catasetum, it is well known that flowers display a remarkably morphological sexual dimorphism. However, it remains poorly investigated whether this is also true for floral scents. Here, we investigated the pollination ecology and floral scent traits (chemistry and total emission) of C. maranhense, a species endemic to the Brazilian N/NE region. Males of Euglossa securigera are the only pollinators of C. maranhense. The floral scent of C. maranhense is composed of 29 volatile compounds, with eucalyptol, indole, (E)-Methyl p-methoxycinnamate, and (Z)-Methyl p-methoxycinnamate accounting for more than 80% of the scent bouquet. No sexual dimorphism was detected in any of the traits investigated. We discuss the ecological and evolutionary significance of our findings to Catasetum species and other unisexual perfume plants.

Environmental Stress Tolerance and Antioxidant Response of Palisada perforata (Rhodophyta) from a Tropical Reef1.

In this study, we analyzed the antioxidant activity and total phenolic content of the intertidal seaweed Palisada perforata collected from different reef microhabitats (sheltered site, tide pool, plateau, and exposed site) along the coast of Pernambuco (Brazil). Both parameters were compared with the same parameters of this species grown in the laboratory under two experiments simulating temperature, salinity, and desiccation conditions found in the reef. After both experiments (temperature x salinity and desiccation), the algal photosynthetic performance was measured through chlorophyll fluorescence parameters using a pulse-amplitude modulation fluorometer to test their stress response. Palisada perforata likely underwent stress by desiccation due to tidal fluctuations rather than to temperature or salinity changes. This conclusion agrees with our observations of the plateau site´s specimens, which were exposed to both air and UV radiation during low tides and exhibited higher antioxidant activity to avoid oxidative damage. However, despite the environmental stress, the antioxidant activity remained low, suggesting that photoinhibition is a crucial protection mechanism against oxidative damage.

A Semivolatile Floral Scent Marks the Shift to a Novel Pollination System in Bromeliads.

Perfume flowers (sensu Vogel1) produce intense scents that function both as attractants and as the sole rewards for pollinators. The scent is collected exclusively by male euglossine bees and used during pre-mating behavior.2-5 Perfume flowers have evolved independently in 15 angiosperm families, with over 1,000 reported species across the Neotropical region.6 Members of Cryptanthus (Bromeliaceae) represent a puzzling exception among perfume flowers, as flowers produce nectar and do not emit a noticeable scent yet still attract euglossine males.7 Here, we studied the pollination ecology of Cryptanthus burle-marxii and decode the chemical communication between its flowers and euglossine males. Field observations revealed euglossine males and hummingbirds as potential pollinators. The bees always contacted anthers/stigma of C. burle-marxii while scraping the petals to obtain chemicals, whereas nectar-seeking hummingbirds normally only contacted the anthers. Based on gas chromatography-mass spectrometry/nuclear magnetic resonance analyses of flower scent samples and bioassays, we identified the diterpene copalol as the only floral scent compound triggering scent-gathering behavior in euglossine males. Unlike euglossine-bee-mediated pollination, hummingbird pollination is ancestral in the Cryptanthus clade, suggesting a case of an ongoing pollinator shift8-10 mediated by the evolution of perfume as a reward. Copalol was previously unknown as a floral scent constituent and represents the heaviest and least-volatile compound known to attract euglossine males. Our study provides the first experimental evidence that semivolatile floral compounds can mediate euglossine bee interactions. Male euglossine pollination in other plant species lacking noticeable floral scents11-13 suggests that semivolatile-mediated pollinator attraction is more widespread than currently appreciated.

Evaluation of Piper marginatum (Piperales: Piperaceae) Oil and Geraniol on the Embryonic Development of Spodoptera frugiperda (Lepidoptera: Noctuidae) in Comparison to Formulated Products.

Essential oils and their isolated constituents are constantly being studied for the control of insect pests. In this context, the present research reports the chemical composition of Piper marginatum (Jacq.) oil aiming to: 1) establish lethal concentrations LC30 and LC50 for this oil and the compound geraniol, 2) histologically examine the embryonic development of Spodoptera frugiperda (J.E. Smith) through light microscopy and scanning electron microscopy (SEM), as well as 3) compare the efficacy of the P. marginatum oil with that of the botanical insecticide azadirachtin, the synthetic insecticide deltamethrin, and acetone as a negative control. Semithin sections of S. frugiperda eggs revealed that the oil, geraniol, azadirachtin, and deltamethrin affected embryonic development at both concentrations. However, geraniol and the oil were more efficient because they caused more significant damage, even at lower concentrations. SEM revealed that all products altered the morphology of the eggs, modifying the structure of the chorion and making the eggs nonviable. Thus, this work demonstrates that P. marginatum oil is effective in the control of S. frugiperda because it results in embryonic damage even at the lowest concentrations.

CdTe-GSH as luminescent biomarker for labeling the larvicidal action of WSMoL lectin in Aedes aegypti larvae.

Mosquito-borne arboviruses compromise human health worldwide. Due to resistance to chemical insecticides, natural compounds have been studied to combat mosquitoes. Previous works have demonstrated a larvicidal activity of the water-soluble Moringa oleifera lectin (WSMoL) against Aedes aegypti, suggesting a mechanism of action based on the interaction between lectin and chitin present in the larvae's peritrophic matrix. In this work, it was investigated the WSMoL activity against Aedes aegypti larvae, by using luminescent bioconjugates of WSMoL conjugated to l-glutathione capped CdTe quantum dots. The conjugation was confirmed by ITC experiments, presenting high enthalpy associated to hydrogen bond interactions between nanoparticles and lectins. The bioconjugate luminescence stability was evaluated by the quantum yield (QY) at different pHs, ionic strengths and heat treatment time. The best parameters reached were pH 7.0, absence of electrolytes and heat treatment, giving QY = 4.4 %. The larvae were exposed to the bioconjugates and analyzed by confocal and fluorescence microscopy. CdTe-WSMol were detected along the entire midgut tract, suggesting a strong interaction with peritrophic matrix and lumen of the Aedes aegypti.

Evaluation of the Activity of the Essential Oil from an Ornamental Flower against Aedes aegypti: Electrophysiology, Molecular Dynamics and Behavioral Assays.

Dengue fever has spread worldwide and affects millions of people every year in tropical and subtropical regions of Africa, Asia, Europe and America. Since there is no effective vaccine against the dengue virus, prevention of disease transmission depends entirely on regulating the vector (Aedes aegypti) or interrupting human-vector contact. The aim of this study was to assess the oviposition deterrent activity of essential oils of three cultivars of torch ginger (Etlingera elatior, Zingiberaceae) against the dengue mosquito. Analysis of the oils by gas chromatography (GC)-mass spectrometry revealed the presence of 43 constituents, of which α-pinene, dodecanal and n-dodecanol were the major components in all cultivars. Solutions containing 100 ppm of the oils exhibited oviposition deterrent activities against gravid Ae. aegypti females. GC analysis with electroantennographic detection indicated that the oil constituents n-decanol, 2-undecanone, undecanal, dodecanal, trans-caryophyllene, (E)-ß-farnesene, α-humulene, n-dodecanol, isodaucene and dodecanoic acid were able to trigger antennal depolarization in Ae. aegypti females. Bioassays confirmed that solutions containing 50 ppm of n-dodecanol or dodecanal exhibited oviposition deterrent activities, while a solution containing the alcohol and aldehyde in admixture at concentrations representative of the oil presented an activity similar to that of the 100 ppm oil solution. Docking and molecular dynamics simulations verified that the interaction energies of the long-chain oil components and Ae. aegypti odorant binding protein 1 were quite favorable, indicating that the protein is a possible oviposition deterrent receptor in the antenna of Ae. aegypti.

Effects of α,ß-unsaturated lactones on larval survival and gut trypsin as well as oviposition response of Aedes aegypti.

Lactones are organic cyclic esters that have been described as larvicides against Aedes aegypti and as components of oviposition pheromone of Culex quinquefasciatus. This work describes the effect of six α,ß-unsaturated lactones (5a-5f) on survival of A. aegypti fourth instar larvae (L4). It is also reported the effects of the lactones on L4 gut trypsin activity and oviposition behavior of A. aegypti females. Five lactones were able to kill L4 being the lactones 5a (LC50 of 39.05 ppm), 5e (LC50 of 36.30 ppm) and 5f (LC50 of 40.46 ppm) the most promising larvicides. Only the lactone 5a inhibited L4 gut trypsin activity, with an IC50 of 115.15 µg/mL. Lactones 5a, 5c, 5d and 5e did not exert deterrent or stimulatory effects on oviposition, whereas lactone 5b exhibited a strong deterrent oviposition activity. In conclusion, this work introduces new α,ß-unsaturated lactones as promising alternatives to control A. aegypti dissemination. The larvicidal mechanism of the lactone 5a can involve the disruption of proteolysis at larval gut.

Assessment of toxicity of Moringa oleifera flower extract to Biomphalaria glabrata, Schistosoma mansoni and Artemia salina.

This study reports the effect of an aqueous extract from Moringa oleifera Lam. flowers on Biomphalaria glabrata embryos and adults and on Schistosoma mansoni adult worms. The extract contains tannins, saponins, flavones, flavonols, xanthones, and trypsin inhibitor activity. The toxicity of the extract on Artemia salina larvae was also investigated to determine the safety of its use for schistosomiasis control. After incubation for 24h, the flower extract significantly (p<0.05) delayed the development of B. glabrata embryos and promoted mortality of adult snails (LC50: 2.37±0.5mgmL(-1)). Furthermore, treatment with the extract disrupted the development of embryos generated by snails, with most of them remaining in the blastula stage while control embryos were already in the gastrula stage. Flower extract killed A. salina larvae with a LC50 value (0.2±0.015mgmL(-1)) lower than that determined for snails. A small reduction (17%) in molluscicidal activity was detected when flower extract (2.37mgmL(-1)) was exposed to tropical environmental conditions (UVI index ranging from 1 to 14, temperature from 25 to 30°C, and 65% relative humidity). Toxicity to A. salina was also reduced (LC50 value of 0.28±0.01mgmL(-1)). In conclusion, M. oleifera flower extract had deleterious effects on B. glabrata adults and embryos. However, unrestricted use to control schistosomiasis should be avoided due to the toxicity of this extract on A. salina.

Extract of Bowdichia virgilioides and maackiain as larvicidal agent against Aedes aegypti mosquito.

The larvicidal activities of extracts of three hardwood species (Hymenaea stigonorcapa, Anadenanthera colubrina and Bowdichia virgilioides) against 4th instar larvae of Aedes aegypti were evaluated using WHO guidelines. Extracts of H. stignocarpa and A. colubrina showed weak activity. The highest larvicidal effect was obtained with the cyclohexane extract of the heartwood of B. virgilioides, which caused 100% mortality at concentrations at 50 and 100 µg/mL. Fraction toluene/EtOAc (8:2) from this extract showed larvicidal activity (LC50 = 34.90 ± 1.27 µg/mL). A mixture of two compounds identified as medicarpin and maackiain exhibited a very good larvicidal activity (sub-fraction 2, LC50 = 17.5 ± 1.87 µg/mL) and maackiain showed to be a strong larvicidal compound (LC50 = 21.95 ± 1.34 µg/mL). This result can be of value in the search for new natural larvicidal compounds from other hardwood plant extracts and presents the first report of B. virgilioides being used to control a mosquito vector.

Effects of Croton rhamnifolioides essential oil on Aedes aegypti oviposition, larval toxicity and trypsin activity.

Although numerous reports are available concerning the larvicidal potential of essential oils, very few investigations have focused on their mechanisms of action. In the present study, we have investigated the chemical composition of the leaf oil of Croton rhamnifolioides during storage and its effects on oviposition and survival of larvae of the dengue fever mosquito Aedes aegypti. In addition, we have established a possible mechanism of action for the larvicidal activity of the essential oil. GC-MS analyses revealed marked differences in the composition of oil that had been freshly isolated and that of a sample that had been stored in a sealed amber-glass vial under refrigeration for three years. However, both fresh and stored oil exhibited substantial larvicidal activities with LC50 values of 122.35 and 89.03 ppm, respectively, and oviposition deterrent effects against gravid females at concentrations of 50 and 100 µg·mL-1. These results demonstrate that the larvicidal effect of the essential oil was unchanged during three years of storage even though its chemical composition altered. Hence, the essential oil could be used in the preparation of commercial products. In addition, we observed that the trypsin-like activity of mosquito larvae was inhibited in vitro by the essential oil of C. rhamnifolioides, suggesting that the larvicidal effect may be associated with inhibition of this enzyme.

Effects of the oral treatment with Copaifera multijuga oil on reproductive performance of male Wistar rats

Copaiba oil, extracted from Copaifera multijuga Hayne, Fabaceae, is widely used for medicinal purposes, especially to treat inflammatory processes. However, there is no report regarding its effect on reproductive performance after used in repeated doses orally. The present study evaluated the effects of the oral administration of Copaiba oil (at doses of 200, 500 or 2500 mg/kg) or water (control) for eight weeks in male Wistar rats. Treated males mated untreated females, and parameters as fertility rates, absolute and relative mass of accessory sexual organs and histology and development of the offspring were evaluated. Chemical analysis revealed the presence of 22 components accounting for 99.11% of the Copaiba oil. The main compounds identified were sesquisterpenes. The reproductive toxicology results indicate that there was no difference between the treated groups compared with the control group in any of the parameters, suggesting that the oral treatment with C. multijuga oil for eight weeks does not affect reproductive performance of male Wistar rats.

The enzyme 3-hydroxykynurenine transaminase as potential target for 1,2,4-oxadiazoles with larvicide activity against the dengue vector Aedes aegypti.

The mosquito Aedes aegypti is the vector agent responsible for the transmission of yellow fever and dengue fever viruses to over 80 million people in tropical and subtropical regions of the world. Exhaustive efforts have lead to a vaccine candidate with only 30% effectiveness against the dengue virus and failure to protect patients against the serotype 2. Hence, vector control remains the most viable route to dengue fever control programs. We have synthesized a class of 1,2,4-oxadiazole derivatives whose most biologically active compounds exhibit potent activity against Aedes aegypti larvae (ca. of 15 ppm) and low toxicity in mammals. Exposure to these larvicides results in larvae pigmentation in a manner correlated with the LC50 measurements. Structural comparisons of the 1,2,4-oxadiazole nucleus against known inhibitors of insect enzymes allowed the identification of 3-hydroxykynurenine transaminase as a potential target for these synthetic larvicides. Molecular docking calculations indicate that 1,2,4-oxadiazole compounds can bind to 3-hydroxykynurenine transaminase with similar conformation and binding energies as its crystallographic inhibitor 4-(2-aminophenyl)-4-oxobutanoic acid.

Differential vulnerability of substantia nigra and corpus striatum to oxidative insult induced by reduced dietary levels of essential fatty acids.

Oxidative stress (OS) has been implicated in the etiology of certain neurodegenerative disorders. Some of these disorders have been associated with unbalanced levels of essential fatty acids (EFA). The response of certain brain regions to OS, however, is not uniform and a selective vulnerability or resilience can occur. In our previous study on rat brains, we observed that a two-generation EFA dietary restriction reduced the number and size of dopaminergic neurons in the substantia nigra (SN) rostro-dorso-medial. To understand whether OS contributes to this effect, we assessed the status of lipid peroxidation (LP) and anti-oxidant markers in both SN and corpus striatum (CS) of rats submitted to this dietary treatment for one (F1) or two (F2) generations. Wistar rats were raised from conception on control or experimental diets containing adequate or reduced levels of linoleic and α-linolenic fatty acids, respectively. LP was measured using the thiobarbituric acid reaction method (TBARS) and the total superoxide dismutase (t-SOD) and catalase (CAT) enzymatic activities were assessed. The experimental diet significantly reduced the docosahexaenoic acid (DHA) levels of SN phospholipids in the F1 (~28%) and F2 (~50%) groups. In F1 adult animals of the experimental group there was no LP in both SN and CS. Consistently, there was a significant increase in the t-SOD activity (p < 0.01) in both regions. In EF2 young animals, degeneration in dopaminergic and non-dopaminergic neurons and a significant increase in LP (p < 0.01) and decrease in the CAT activity (p < 0.001) were detected in the SN, while no inter-group difference was found for these parameters in the CS. Conversely, a significant increase in t-SOD activity (p < 0.05) was detected in the CS of the experimental group compared to the control. The results show that unbalanced EFA dietary levels reduce the redox balance in the SN and reveal mechanisms of resilience in the CS under this stressful condition.

Effect of Moringa oleifera lectin on development and mortality of Aedes aegypti larvae.

Aedes aegypti larvae have developed tolerance to many insecticides used for mosquito control. Moringa oleifera seeds contain a water-soluble lectin (WSMoL) and this paper reports the effect of M. oleifera seed extracts (MoE(1-15)) and WSMoL on development and survival of A. aegypti larvae. WSMoL peptide from in-gel trypsin digestion is also described. MoE(1-15) showed hemagglutinating activity and WSMoL had similarity with flocculating proteins from M. oleifera seeds. MoE(1) and MoE(3) delayed larval development which stopped in the third instar (L3) in MoE(6) and MoE(15). Significant (p<0.0001) larval mortality was only detected in MoE(15). Native WSMoL showed larvicidal activity (LC(50) 0.197 mg mL(-1)) and heated lectin, without hemagglutinating activity, did not kill fourth instar (L4) larvae. Optical microscopy showed that live L4 from MoE(1) presented underlying epithelium, increased gut lumen and hypertrophic segments; dead L4 from WSMoL were absent of underlying epithelium, had increased gut lumen and hypertrophic segments. The presence of hemagglutinating activity in the extracts suggests that soluble lectin promotes the delay of larval development and mortality; furthermore, the absence of larvicidal activity in heat-denatured WSMoL strengthens the involvement of lectin in this activity mechanism.