Sybille Lorenz

Resistance of Australian Helicoverpa armigera to fenvalerate is due to the chimeric P450 enzyme CYP337B3

Worldwide, increasing numbers of insects have evolved resistance to a wide range of pesticides, which hampers their control in the field and, therefore, threatens agriculture. Members of the carboxylesterase and cytochrome P450 monooxygenase superfamilies are prominent candidates to confer metabolic resistance to pyrethroid insecticides. Both carboxylesterases and P450 enzymes have been shown to be involved in pyrethroid resistance in Australian Helicoverpa armigera, the noctuid species possessing by far the most reported resistance cases worldwide. However, specific enzymes responsible for pyrethroid resistance in field populations of this species have not yet been identified. Here, we show that the resistance toward fenvalerate in an Australian strain of H. armigera is due to a unique P450 enzyme, CYP337B3, which arose from unequal crossing-over between two parental P450 genes, resulting in a chimeric enzyme. CYP337B3 is capable of metabolizing fenvalerate into 4′-hydroxyfenvalerate, which exhibits no toxic effect on susceptible larvae; enzymes from the parental P450 genes showed no detectable fenvalerate metabolism. Furthermore, a polymorphic H. armigera strain could be bred into a susceptible line possessing the parental genes CYP337B1 and CYP337B2 and a resistant line possessing only CYP337B3. The exclusive presence of CYP337B3 in resistant insects of this strain confers a 42-fold resistance to fenvalerate. Thus, in addition to previously documented genetic mechanisms of resistance, recombination can also generate selectively advantageous variants, such as this chimeric P450 enzyme with an altered substrate specificity leading to a potent resistance mechanism.

Host strain specific sex pheromone variation in Spodoptera frugiperda

BackgroundThe fall armyworm Spodoptera frugiperda (Lepidoptera; Noctuidae) consists of two distinct strains with different host plant preferences for corn and rice. To assess whether pheromonal-mediated behavioral isolation accompanies the habitat isolation on different host plants, we compared the sex pheromone composition among females of the two strains. Pheromone glands were extracted with or without injection of pheromone biosynthesis activating neuropeptide (PBAN). To assess the mode of inheritance of this variation, we also analyzed the pheromone composition of F1 hybrid females.ResultsRelative to intra-strain variation, the pheromone composition of the two strains differed significantly. Corn strain females contained significantly more of the second most abundant pheromone compound Z11-16:Ac (m), and significantly less of most other compounds, than rice strain females. When females were injected with PBAN before their glands were extracted, the differences between the strains were less pronounced but still statistically significant. The pheromone composition of hybrid females showed a maternal inheritance of the major component Z9-14:Ac (M) as well as of Z11-16:Ac (m). Most other compounds showed an inheritance indicating genetic dominance of the corn strain. The within-strain phenotypic correlations among the various components were consistent with their hypothesized biosynthetic pathway, and between-strain differences in the correlation structure suggested candidate genes that may explain the pheromone differences between the two strains. These include Δ9- and Δ11 desaturases, and possibly also a Δ7-desaturase, although the latter has not been identified in insects so far.ConclusionThe two host strains of S. frugiperda produce systematically differing female sex pheromone blends. Previously-documented geographic variation in the sexual communication of this species did not take strain identity into account, and thus may be partly explained by different strain occurrence in different regions. The finding of pheromone differences reinforces the possibility of incipient reproductive isolation among these strains, previously shown to differ in the timing of nocturnal mating activity and host plant use. Finding the genetic basis of the pheromone differences, as well as these other biological traits, will help to elucidate the role of premating isolation in the continuing differentiation of these two strains that may eventually lead to speciation.

Preparation and synthetic application of partially protected brassinosteroids

Preparation of partially protected brassinosteroids is achieved through the reaction of the source material (24-epicastasterone and 24-epibrassinolide) with diol-specific reagents (2,2-dimethoxypropane and methylboronic acid). The obtained products were shown to be useful synthetic intermediates for further preparation of minor representatives of this class of natural phytohormones (such as 3,24-diepicastasterone and 3-dehydro-24-epibrassinolide).

Inhibition of 5-lipoxygenase as anti-inflammatory mode of action of Plectranthus zeylanicus Benth and chemical characterization of ingredients by a mass spectrometric approach.

ETHNOPHARMACOLOGICAL RELEVANCE The perennial herb Plectranthus zeylanicus Benth is extensively used in traditional medicine in Sri Lanka and South India for treating inflammatory conditions, but pharmacological features of Plectranthus zeylanicus are hardly explored in order to understand and rationalize its use in ethnomedicine. As 5-lipoxygenase (5-LO) is a key enzyme in inflammatory disorders such as asthma or atherosclerosis, we investigated 5-LO inhibition by Plectranthus zeylanicus extracts and analyzed relevant constituents. MATERIALS AND METHODS We applied cell-free and cell-based assays to investigate suppression of 5-LO activity. Cell viability, radical scavenger activities, and inhibition of reactive oxygen species formation (ROS) in neutrophils were analysed to exclude unspecific cytotoxic or antioxidant effects. Constituents of the extracts were characterized by bioassay-guided fractionation and by analysis using gas or liquid chromatography coupled to mass spectrometric (Orbitrap) analysis. RESULTS Extracts of Plectranthus zeylanicus prepared with n-hexane or dichloromethane potently suppressed 5-LO activity in stimulated human neutrophils (IC50=6.6 and 12µg/ml, respectively) and inhibited isolated human recombinant 5-LO (IC50=0.7 and 1.2µg/ml, respectively). In contrast, no significant radical scavenging activity or suppression of ROS formation was observed, and neutrophil viability was unaffected. Besides ubiquitously occurring ingredients, coleone P, cinncassiol A and C, and callistric acid were identified as constituents in the most active fraction. CONCLUSIONS Together, potent inhibition of 5-LO activity, without concomitant anti-oxidant activity and cytotoxic effects, rationalizes the ethnopharmacological use of Plectranthus zeylanicus as anti-inflammatory remedy. Modern chromatographic/mass spectrometric analysis reveals discrete chemical structures of relevant constituents.

Unprecedented Utilization of Pelargonidin and Indole for the Biosynthesis of Plant Indole Alkaloids

Nudicaulins are a group of indole alkaloid glycosides responsible for the color of yellow petals of Papaver nudicaule (Iceland poppy). The unique aglycone scaffold of these alkaloids attracted our interest as one of the most unusual flavonoid‐indole hybrid structures that occur in nature. Stable isotope labeling experiments with sliced petals identified free indole, but not tryptamine or l‐tryptophan, as one of the two key biosynthetic precursors of the nudicaulin aglycone. Pelargonidin was identified as the second key precursor, contributing the polyphenolic unit to the nudicaulin molecule. This finding was inferred from the temporary accumulation of pelargonidin glycosides in the petals during flower bud development and a drop at the point in time when nudicaulin levels start to increase. The precursor‐directed incorporation of cyanidin into a new 3′‐hydroxynudicaulin strongly supports the hypothesis that anthocyanins are involved in the biosynthesis of nudicaulins.

Foetithiophenes C-F, thiophene derivatives from the roots of Ferula foetida

Abstract Context: Ferula foetida Regel (Apiaceae) is an Iranian medicinal plant with various biological activities including antispasmodic and anthelmintic. Objective: The sulfur compounds from the roots of F. foetida were isolated and characterized to test their cytotoxic and antimicrobial activities. Materials and methods: The methanolic extract of the roots of F. foetida was fractionated using silica column chromatography. The components of each fraction were further purified using RP-HPLC. Their structures were elucidated by 1- and 2-D NMR spectroscopy as well as HREIMS. Their cytotoxic and antimicrobial activities were evaluated using Alamar Blue assay and broth microdilution method, respectively. Results: Four new thiophene derivatives, namely foetithiophenes C-F (3–6), together with four known compounds, foetithiophenes A (1) and B (2), coniferaldehyde, and sinapic aldehyde, were isolated from the roots of F. foetida. Antimicrobial activities were observed in particular against the Gram-positive bacteria. The best antimicrobial activity was observed for compound 6 against B. cereus with a MIC value 50 µg/mL. The tested compounds did not show cytotoxic properties against MCF-7 and K562 cells. Conclusion: Four new thiophene derivatives including foetithiophenes C-F (3–6) were characterized from the roots of F. foetida. Foetithiophene F (6) exhibited the most potent activity against the Gram-positive bacteria B. cereus.

The absolute configuration of salicortin, HCH-salicortin and tremulacin from Populus trichocarpa × deltoides Beaupré

The absolute configuration of salicortin, HCH-salicortin and tremulacin, isolated from leaves of Populus trichocarpa × deltoides Beaupré, was determined by comparing spectroscopic data of these compounds with those of idescarpin, isolated from leaves of Idesia polycarpa. All compounds were characterized by nuclear magnetic resonance spectroscopy, high-resolution mass spectrometry, and circular dichroism spectroscopy. It was found that the hydroxy cyclohexenonoyl (HCH) moiety in all compounds is (S)-configured. In addition, it was shown that leaves of Idesia polycarpa contain high amounts of (−)-idescarpin (1.1%, based on dry weight).

Sulfur-containing compounds from the roots of Ferula latisecta and their cytotoxic activities

Five new sulfur-containing compounds, with a new geometry (cis) of the propenyl moiety, and five known compounds were isolated from the roots of Ferula latisecta. The structures of these compounds, were elucidated on the basis of spectroscopic data including 1D and 2D NMR experiments and HRMS. All of the isolated compounds were tested against A2780, A549, HeLa, and HCT116 human cancer cell lines and some of them showed moderate cytotoxic activities.

Munronia pinnata (Wall.) Theob.: Unveiling phytochemistry and dual inhibition of 5-lipoxygenase and microsomal prostaglandin E2 synthase (mPGES)-1

ETHNOPHARMACOLOGICAL RELEVANCE Preparations from Munronia pinnata (Wall.) Theob. are extensively used in traditional medicine in Sri Lanka for the treatment of inflammatory conditions. However, neither the pharmacological features nor the phytochemistry of this plant are explored in order to understand and rationalize the reported ethnobotanical significance. As 5-lipoxygenase (5-LO) and microsomal prostaglandin E2 synthase (mPGES)-1 are crucial enzymes in inflammatory disorders, we evaluated their inhibition by M. pinnata extracts and studied the chemical profile of the plant for the identification of relevant constituents. MATERIALS AND METHODS Cell-free and cell-based assays were employed in order to investigate the suppression of 5-LO and mPGES-1 activity. Cell viability, radical scavenger activities, and inhibition of reactive oxygen species formation (ROS) in neutrophils were studied to assess cytotoxic and antioxidant effects. Gas and liquid chromatography coupled to mass spectrometric analysis enabled the characterization of secondary metabolites. RESULTS The n-hexane extract of M. pinnata efficiently suppressed 5-LO activity in stimulated human neutrophils (IC50 =8.7µg/ml) and potently inhibited isolated human recombinant 5-LO (IC50 =0.48µg/ml) and mPGES-1 (IC50 =1.0µg/ml). In contrast, no significant radical scavenging activity or suppression of ROS formation was observed, and neutrophil viability was unaffected. The phytochemistry of the plant was unveiled for the first time and phytosterols, fatty acids, sesquiterpenes and several other types of secondary metabolites were identified. CONCLUSIONS Together, potent inhibition of 5-LO and mPGES-1 activity, without concomitant antioxidant activity and cytotoxic effects, rationalizes the ethnopharmacological use of M. pinnata as anti-inflammatory remedy. Detailed chromatographic/mass spectrometric analysis reveals discrete chemical structures of relevant constituents.

Lipophilic extracts of Leucas zeylanica, a multi-purpose medicinal plant in the tropics, inhibit key enzymes involved in inflammation and gout

ETHNOPHARMACOLOGICAL RELEVANCE Leucas zeylanica (L.) W.T. Aiton is a popular, multi-purpose medicinal plant in Sri Lanka but the pharmacological potential and the chemical profile have not been systematically investigated to understand and rationalize the reported ethnobotanical significance. AIM OF THE STUDY The present study was undertaken to scientifically validate the traditional usage of this plant for the treatment of inflammatory conditions, gout and microbial infections. Inhibition of 5-lipoxygenase (5-LO), microsomal prostaglandin E2 synthase (mPGES)-1 and xanthine oxidase (XO) by different extracts of L. zeylanica was investigated to determine the anti-inflammatory and anti-gout activity, respectively. The antibacterial and antifungal activities were also studied and the relevant constituents in the bioactive extracts were tentatively identified. MATERIALS AND METHODS Cell-free and/or cell-based assays were employed in order to investigate the effects of the extracts against the activity of human 5-LO, mPGES-1 and XO as well as to assess antioxidant properties. The antibacterial activity of the extracts was determined by the broth micro-dilution method against Gram positive and Gram negative bacteria including methicillin-resistant Staphylococcus aureus while the agar dilution method was employed to determine the anti-Candida activity. Gas chromatography coupled to mass spectrometric (GC-MS) analysis enabled the characterization of secondary metabolites in the extracts. RESULTS The dichloromethane extract of L. zeylanica efficiently inhibited 5-LO activity in stimulated human neutrophils (IC50 = 5.5 µg/mL) and isolated human 5-LO and mPGES-1 (IC50 = 2.2 and 0.4 µg/mL). Potent inhibition of XO was observed by the same extract (IC50 = 47.5 μg/mL), which is the first report of XO-inhibitory activity of a Sri Lankan medicinal plant. Interestingly, significant radical scavenging activity was not observed by this extract. Only the n-hexane extract exhibited antibacterial activity against Staphylococcus aureus and Staphylococcus saprophyticus with a MIC of 250 µg/mL while the anti-Candida activity was moderate. GC-MS analysis revealed the presence of phytosterols, fatty acids, sesquiterpenes, diterpenes and several other types of secondary metabolites. CONCLUSIONS Potent inhibition of 5-LO, mPGES-1 and XO rationalizes the ethnopharmacological use of L. zeylanica as anti-inflammatory and anti-gout remedy. Interestingly, the antimicrobial activities were not prominent, despite its wide utility as an antimicrobial medication.