Carnivorous Plants from Nepenthaceae and Droseraceae as a Source of Secondary Metabolites.

Carnivorous plants are able to attract small animals or protozoa and retain them in their specialized traps. Later, the captured organisms are killed and digested. The nutrients contained in the prey bodies are absorbed by the plants to use for growth and reproduction. These plants produce many secondary metabolites involved in the carnivorous syndrome. The main purpose of this review was to provide an overview of the secondary metabolites in the family Nepenthaceae and Droseraceae, which were studied using modern identification techniques, i.e., high-performance liquid chromatography or ultra-high-performance liquid chromatography with mass spectrometry and nuclear magnetic resonance spectroscopy. After literature screening, there is no doubt that tissues of species from the genera Nepenthes, Drosera, and Dionaea are rich sources of secondary metabolites that can be used in pharmacy and for medical purposes. The main types of the identified compounds include phenolic acids and their derivatives (gallic, protocatechuic, chlorogenic, ferulic, p-coumaric acids, gallic, hydroxybenzoic, vanillic, syringic caffeic acids, and vanillin), flavonoids (myricetin, quercetin, and kaempferol derivatives), including anthocyanins (delphinidin-3-O-glucoside, cyanidin-3-O-glucoside, and cyanidin), naphthoquinones (e.g., plumbagin, droserone, and 5-O-methyl droserone), and volatile organic compounds. Due to the biological activity of most of these substances, the importance of the carnivorous plant as a pharmaceutical crop will increase.

Ultrasensitive Bioelectronic Tongue Based on the Venus Flytrap Domain of a Human Sweet Taste Receptor.

Sweet taste is an important factor that regulates calorie intake and contributes to food preferences in humans and animals. Therefore, the evaluation of sweet substances is essential for various fields such as healthcare, food, and pharmaceutical industries. Sweet tastants are detected by sweet taste receptors which are class C G-protein-coupled receptors. T1R2 venus flytrap (VFT) of the sweet taste receptor is known as a primary ligand-binding domain for sweet tastants. In this study, we developed an ultrasensitive artificial sweet taste bioelectronic tongue based on the T1R2 VFT of a human sweet taste receptor. Here, the T1R2 VFT of a human sweet taste receptor was successfully overexpressed in a bacterial expression system. A T1R2 VFT-immobilized carbon nanotube field-effect transistor with floating electrodes was exploited as an artificial sweet taste sensory system. Significantly, our T1R2 VFT-functionalized bioelectronic tongue could be used to detect solutions of sweet tastants down to 0.1 fM and selectively discriminate sweet substances from other taste substances. Furthermore, our device could be used to monitor the response of the T1R2 VFT domain of a sweet taste receptor to sweet substances in real food environments such as apple juice and chamomile herb tea. Moreover, our device was used to evaluate the inhibition and enhancement effects on sweet taste receptors by zinc ions and chamomile tea, respectively. In addition, our device demonstrated long-term storability and reusability. In this respect, our sweet taste bioelectronic tongue could be a promising tool for various basic research and industrial applications.

The aquatic carnivorous plant Aldrovanda vesiculosa (Droseraceae) exhibits altered developmental stages in male gametophyte.

Aldrovanda vesiculosa (Droseraceae) is a rare aquatic carnivorous plant, distributed in Europe, Asia, Africa, and Australia. Aldrovanda populations can flower prolifically under favourable conditions, but seed set is very limited. We studied the structure of Aldrovanda pollen collected from flowers in different developmental stages (opened and non-opened anthers) from both European and Australian populations to elucidate pollination traits and the basis of poor seed set on the basis of microscopic observation of pollen and anther structure. Microscopic analyses of Aldrovanda pollen showed that this plant has pollen arranged in tetrads like other species in the Droseraceae family. In hydrated pollen, cytoplasmic protrusions originate from pores located along the equatorial wall of monads, and can develop into pollen tubes. Interestingly, pollen development from microspores occurs in open anthers, suggesting a delay of the developmental stages. In addition, pollen development displays altered sperm cell formation and precocious pollen germination. Precocious germination may characterize recalcitrant pollen, which naturally do not undergo dehydration before anthesis and remain partially hydrated, particularly in aquatic and wetland plants. These alterations of male gametophyte development could affect fertilization processes, and be the reason for the low reproductive capability of Aldrovanda observed both in the field and in cultures. Generally, reduced pollen longevity and very quick germination are considered an adaptation to aquatic or wet environments.

A Chemometry of Aldrovanda vesiculosa L. (Waterwheel, Droseraceae) Populations.

The genus Aldrovanda is a Palaeogene element containing a single extant species, Aldrovanda vesiculosa L. This aquatic carnivorous herb has a very wide range of distribution, natively covering four continents; however, it is a critically endangered aquatic plant species worldwide. Previous studies revealed that A. vesiculosa had an extremely low genetic variation. The main aim of the present paper is to explore, using chemometric tools, the diversity of 16 A. vesiculosa populations from various sites from four continents (Eurasia, Africa, Australia). Using chemometric data as markers for genetic diversity, we show the relationships of 16 A. vesiculosa populations from various sites, including four continents. Phytochemical markers allowed the identification of five well-supported (bootstrap > 90%) groups among the 16 populations sampled. The principal component analysis data support the idea that the strongly related African (Botswana) and Australian (Kimberley, NT, NW Australia) populations are the most distant ones, separated from the European and Asian ones. However, considering the five Australian populations sampled, three are nested within the Eurasian group. The chemometric data are correlated positively with the geographical distances between the samples, which suggests a tendency toward isolation for the most distant populations.

Elicitation-Based Method for Increasing the Production of Antioxidant and Bactericidal Phenolic Compounds in Dionaea muscipula J. Ellis Tissue.

The carnivorous plant Dionaea muscipula J. Ellis (Venus flytrap) is a widely known medical herb, capable of producing various phenolic compounds known for their strong antioxidant and antibacterial properties. In the pharmaceutical industry, Venus flytrap is grown in tissue cultures, as the natural population of D. muscipula is very limited. Here, we describe an improved method to increase the quantity and quality of phenolic compounds produced in D. muscipula. This is achieved by combining biotic elicitation (using Cronobacter sakazakii bacteria lysate) of D. muscipula cultured with rotary shaking (hydromechanical stress), which we describe here for the first time. The antibacterial activity and the antioxidant properties of the obtained compounds were studied on two antibiotic-resistant human pathogenic bacteria. The proposed plant culture conditions resulted in an increase in fresh weight, as well as a higher total phenolic content, in comparison to traditional tissue cultures on agar-solidified medium. With the use of high-performance liquid chromatography, we demonstrated that the described elicitation strategy leads to an increased synthesis of myricetin, caffeic acid, ellagic acid and plumbagin in D. muscipula tissue. We also found that a higher level of antioxidant activity, exhibited by the plant extract, corresponded with its higher phenylpropanoid content. The bactericidal activity of the extract against Staphylococcus aureus was dependent on the duration of plant culture under described elicitation conditions, whereas neither elicitation condition (duration or elicitor concentration) seemed relevant for the bactericidal activity of the extract towards Escherichia coli. This suggest that Gram-negative bacteria are less sensitive to compounds derived from Venus flytrap tissue.

Is a blue-red light a good elicitor of phenolic compounds in the family Droseraceae? A comparative study.

Plants from the family Droseraceae, especially Drosera sp. and Dionaea sp., are naturally rich in phenolic derivatives such as plumbagin, among others. Plumbagin is known both for its pharmacological significance and its protective properties against light stress. Light stress - high light intensity or/and light spectral composition - activates plants' response mechanisms including, among others, hormonal (salicylic acid, jasmonic acid) pathways and secondary metabolite (phenolic compounds, proline) pathways. Short-wavelength radiation, due to its high energy, will induce the synthesis of protective secondary metabolites, including those with pharmaceutical properties. The aim of the study was to describe and compare acclimation strategies of Drosera peltata and Dionaea muscipula to blue-red light in the context of phenolic compound accumulation, and salicylic acid, jasmonic acid and proline synthesis. For the first time, differences in the responses of D. muscipula and D. peltata to blue-red light (in the ratio 6:1) were established. In Dionaea sp., it was associated with the use of redox equivalents (in particular, plastoquinone pool) for the synthesis of primary metabolites used in the process of growth and development. In Drosera sp., a rapid adjustment of redox state led to the synthesis of secondary metabolites, constituting a reservoir of carbon skeletons and allowing for a quick defence response to stress factors. In both species, blue-red light did not induce the jasmonic acid pathway. However, the salicylic acid pathway was induced as an alternative to the phenolic compound synthesis pathway. Nevertheless, the applied blue-red light was not an effective elicitor of phenolic compounds in the plants examined.

How water flow, geometry, and material properties drive plant movements.

Plants are dynamic. They adjust their shape for feeding, defence, and reproduction. Such plant movements are critical for their survival. We present selected examples covering a range of movements from single cell to tissue level and over a range of time scales. We focus on reversible turgor-driven shape changes. Recent insights into the mechanisms of stomata, bladderwort, the waterwheel, and the Venus flytrap are presented. The underlying physical principles (turgor, osmosis, membrane permeability, wall stress, snap buckling, and elastic instability) are highlighted, and advances in our understanding of these processes are summarized.

Digestive glands extraction and precise pigment analysis support the exclusion of the carnivorous plant Dionaea muscipula Ellis from the Caryophyllales order.

In the order Caryophyllales, plants synthesize betalains instead of anthocyanins, with only two exceptions, the Caryophyllaceae and Molluginaceae. Dionaea muscipula Ellis was included in the Caryophyllales order but recent research based on genetic studies proposed the consideration of the Droseraceae family into the Nepenthales order. In this work we face the dilemma of the phylogenetic classification of Dionaea from a phytochemical point of view. Dionaea's pigments were analyzed by using techniques of structural analysis. Extracts from the leaves, mature stem and flowers of different specimens of Dionaea were analyzed, to find possible differences in the types of pigments or in their proportion in different parts of the plant. These extracts were analyzed by spectrophotometry, HPLC co-elution and ESI-MS/MS. In addition, digestive glands were extracted from the snap trap with minor sample manipulation and by reducing the non-pigmented plant tissue. Considering only the digestive glands instead of whole snap traps, the analyses allowed to quantitate and elucidate the structure of the compounds responsible for the red coloration: delphinidin-3-O-glucoside (myrtillin), cyanidin-3-O-glucoside (kuromanin) and a third compound, the aglycone cyanidin, detected in the species for the first time. The unambiguous results of the present work support the exclusion of Dionaea from the Caryophyllales.

The structure of Plasmodium falciparum 3D7_0606800 reveals a bi-lobed architecture that supports re-annotation as a Venus Flytrap protein.

Plasmodium falciparum, the causative agent of malaria, employs a diverse array of surface displayed proteins to promote dissemination and establish infection in the human host. Of these, Pf3D7_0606800 is highly immunogenic and has been designated a potential top 10 candidate for inclusion in a multicomponent malarial vaccine. The role of Pf3D7_0606800 in parasite biology, however, is unknown and its characterization has been complicated by a lack of sequence identity with proteins of known structure or function. Towards elucidating Pf3D7_0606800 function, we determined its structure to a resolution of 2.35 Å using selenium single wavelength anomalous dispersion. A bi-lobed architecture displays the core structural hallmarks of Venus Flytrap (VFT) proteins prompting us to re-annotate Pf3D7_0606800 as PfVFT1. Structural analysis further revealed an extended inter-lobe groove that, when interrogated by molecular docking, appears well suited to bind peptide-based ligands. Collectively, our structural characterization of the highly antigenic P. falciparum surface protein PfVFT1 provides intriguing functional insight and establishes a structural template that could prove valuable for malaria vaccine engineering studies.

Anticancer Properties and Pharmaceutical Applications of Plumbagin: A Review.

It has been shown that plumbagin, a bioactive naphthoquinone isolated from three major plant families viz. Plumbaginaceae, Ebenceae and Droseraceae, definitively exhibits anticancer potential in diverse cancer cells both in vitro and in vivo. Plumbagin shows antineoplastic effects via multi-channel molecular mechanisms, including the induction of apoptosis and autophagy, the disruption of the cell cycle, the inhibition of invasion and metastasis, and anti-angiogenesis. Plumbagin inhibits the growth of cancer cells mainly through the modulation of the signals of PI3K/Akt/mTOR, AMPK, Ras, and so on. The pharmaceutical applications of plumbagin combined with nanocarriers to achieve better therapeutic efficiency are discussed in this review Among them, liposomes, nanoparticles, microspheres, micelles, and nisosomes are used in cancer treatment. The anticancer study of plumbagin in vivo is also summarized in this review. On the whole, we aim to review the research progress of plumbagin both in pharmacological and pharmaceutical filed, which may provide some reference for further research of plumbagin.

Virulence regulation with Venus flytrap domains: structure and function of the periplasmic moiety of the sensor-kinase BvgS.

Two-component systems (TCS) represent major signal-transduction pathways for adaptation to environmental conditions, and regulate many aspects of bacterial physiology. In the whooping cough agent Bordetella pertussis, the TCS BvgAS controls the virulence regulon, and is therefore critical for pathogenicity. BvgS is a prototypical TCS sensor-kinase with tandem periplasmic Venus flytrap (VFT) domains. VFT are bi-lobed domains that typically close around specific ligands using clamshell motions. We report the X-ray structure of the periplasmic moiety of BvgS, an intricate homodimer with a novel architecture. By combining site-directed mutagenesis, functional analyses and molecular modeling, we show that the conformation of the periplasmic moiety determines the state of BvgS activity. The intertwined structure of the periplasmic portion and the different conformation and dynamics of its mobile, membrane-distal VFT1 domains, and closed, membrane-proximal VFT2 domains, exert a conformational strain onto the transmembrane helices, which sets the cytoplasmic moiety in a kinase-on state by default corresponding to the virulent phase of the bacterium. Signaling the presence of negative signals perceived by the periplasmic domains implies a shift of BvgS to a distinct state of conformation and activity, corresponding to the avirulent phase. The response to negative modulation depends on the integrity of the periplasmic dimer, indicating that the shift to the kinase-off state implies a concerted conformational transition. This work lays the bases to understand virulence regulation in Bordetella. As homologous sensor-kinases control virulence features of diverse bacterial pathogens, the BvgS structure and mechanism may pave the way for new modes of targeted therapeutic interventions.

Flytrap-inspired robot using structurally integrated actuation based on bistability and a developable surface.

The Venus flytrap uses bistability, the structural characteristic of its leaf, to actuate the leaf's rapid closing motion for catching its prey. This paper presents a flytrap-inspired robot and novel actuation mechanism that exploits the structural characteristics of this structure and a developable surface. We focus on the concept of exploiting structural characteristics for actuation. Using shape memory alloy (SMA), the robot actuates artificial leaves made from asymmetrically laminated carbon fiber reinforced prepregs. We exploit two distinct structural characteristics of the leaves. First, the bistability acts as an implicit actuator enabling rapid morphing motion. Second, the developable surface has a kinematic constraint that constrains the curvature of the artificial leaf. Due to this constraint, the curved artificial leaf can be unbent by bending the straight edge orthogonal to the curve. The bending propagates from one edge to the entire surface and eventually generates an overall shape change. The curvature change of the artificial leaf is 18 m(-1) within 100 ms when closing. Experiments show that these actuation mechanisms facilitate the generation of a rapid and large morphing motion of the flytrap robot by one-way actuation of the SMA actuators at a local position.

Antimicrobial activity of the carnivorous plant Dionaea muscipula against food-related pathogenic and putrefactive bacteria.

Solvent extracts from the carnivorous plant Dionaea muscipula (Venus flytrap) were prepared using eight different organic solvents, and examined for antibacterial activity against food-related pathogenic and putrefactive bacteria. All solvent extracts showed higher antibacterial activity against gram positive bacteria than against gram negative bacteria. The TLC-bioautography analysis of the extracts revealed that a yellow spot was detected at Rf value of 0.85, which showed strong antibacterial activity. The UV, MS, and NMR analyses revealed that the antibacterial compound was plumbagin.

Shape-changing shell-like structures.

Plants such as Dionaea muscipula (Venus Flytrap) can change the shape of their shell-like leaves by actively altering the cell pressures. These leaves are hydraulic actuators that do not require any complex controls and that possess an energy efficiency that is unmatched by natural or artificial muscles (Huber et al 1997 Proc. R. Soc. A 453 2185-205). We extend our previous work (Pagitz et al 2012 Bioinspir. Biomim. 7 016007) on pressure-actuated cellular structures by introducing a concept for shape-changing shell-like structures that can significantly alter their Gaussian curvature. The potential of this concept is demonstrated by a hemispherical shell that can reversibly change the sign of its Gaussian curvature. Furthermore, it is shown that a snap-through behaviour, similar to the one known from Dionaea muscipula, can be achieved by lowering the pressure in a single layer of cells.

Phenolic metabolites in carnivorous plants: Inter-specific comparison and physiological studies.

Despite intensive phytochemical research, data related to the accumulation of phenols in carnivorous plants include mainly qualitative reports. We have quantified phenolic metabolites in three species: Drosera capensis, Dionaea muscipula and Nepenthes anamensis in the "leaf" (assimilatory part) and the "trap" (digestive part). For comparison, commercial green tea was analysed. Phenylalanine ammonia-lyase (PAL) activities in Dionaea and Nepenthes were higher in the trap than in the leaf while the opposite was found in Drosera. Soluble phenols and majority of phenolic acids were mainly accumulated in the trap among species. Flavonoids were abundant in Drosera and Dionaea traps but not in Nepenthes. Phenolic acids were preferentially accumulated in a glycosidically-bound form and gallic acid was the main metabolite. Green tea contained more soluble phenols and phenolic acids but less quercetin. In vitro experiments with Drosera spathulata revealed that nitrogen deficiency enhances PAL activity, accumulation of phenols and sugars while PAL inhibitor (2-aminoindane-2-phosphonic acid) depleted phenols and some amino acids (but free phenylalanine and sugars were elevated). Possible explanations in physiological, biochemical and ecological context are discussed.

Activity against Mycobacterium smegmatis and M. tuberculosis by extract of South African medicinal plants.

Seven ethnobotanically selected medicinal plants were screened for their antimycobacterial activity. The minimum inhibitory concentration (MIC) of four plants namely Artemisia afra, Dodonea angustifolia, Drosera capensis and Galenia africana ranged from 0.781 to 6.25 mg/mL against Mycobacterium smegmatis. G. africana showed the best activity exhibiting an MIC of 0.78 mg/mL and a minimum bactericidal concentration (MBC) of 1.56 mg/mL. The MICs of ethanol extracts of D. angustifolia and G. africana against M. tuberculosis were found to be 5.0 and 1.2 mg/mL respectively. The mammalian cytotoxicity IC(50) value of the most active antimycobacterial extract, from G. africana, was found to be 101.3 microg/mL against monkey kidney Vero cells. Since the ethanol G. africana displayed the best antimycobacterial activity, it was subjected to fractionation which led to the isolation of a flavone, 5,7,2'-trihydroxyflavone. The MIC of this compound was found to be 0.031 mg/mL against M. smegmatis and 0.10 mg/mL against M. tuberculosis. This study gives some scientific basis to the traditional use of these plants for TB-related symptoms.

Using of liquid chromatography coupled with diode array detector for determination of naphthoquinones in plants and for investigation of influence of pH of cultivation medium on content of plumbagin in Dionaea muscipula.

The interest of many investigators in naphthoquinones is due to their broad-range of biological actions from phytotoxic to fungicidal. The main aim of this work was to investigate the influence of different pH values of cultivation medium on naphthoquinone content in Dionaea muscipula. For this purpose, we optimized the simultaneous analysis of the most commonly occurring naphthoquinones (1,4-naphthoquinone, lawsone, juglone and plumbagin) by high performance liquid chromatography coupled with diode array detector (HPLC-DAD). The most suitable chromatographic conditions were as follows: mobile phase: 0.1 mol l-1 acetic acid:methanol in ratio of 33:67 (%, v/v), flow rate: 0.75 ml min-1 and temperature: 42 degrees C. Moreover, we looked for the most suitable technique for preparation of plant samples (D. muscipula, Juglans regia, Paulownia tomentosa, Impatience glandulifera, Impatience parviflora, Drosera rotundifolia, Drosera spathulata and Drosera capensis) due to their consequent analysis by HPLC-DAD. It clearly follows from the results obtained that sonication were the most suitable technique for preparation of J. regia plants. We also checked the recoveries of the determined naphthoquinones, which were from 96 to 104%. Finally, we investigated the changes in content of plumbagin in D. muscipula plants according to different pH of cultivation medium. The content increased with increasing pH up to 5 and, then, changed gradually. The lower content of plumbagin at lower pH values was of interest to us. Therefore, we determined the content of this naphthoquinone in the cultivation medium, what has not been studied before. We discovered that the lower tissue content of plumbagin was due to secretion of this naphthoquinone into the cultivation medium.

Naphthalene glucoside and other phenolics from the shoot and callus cultures of Drosophyllum lusitanicum.

The callus and, for the first time established, shoot cultures of Drosophyllum lusitanicum Link. (Droseraceae) yielded new naphthalene glucoside-5-hydroxy-4-methoxy-2-naphthalenecarboxylic acid 5-O-beta-glucoside (drosophylloside) and 5-hydroxy-4-methoxy-2-naphthalenecarboxylic acid methyl ester besides other phenolics like naphthalenes-5-hydroxy-4-methoxy-2-naphthalenecarboxylic acid (ancistronaphthoic acid B), hydroplumbagin 4-O-glucoside, naphthoquinones-plumbagin and 3-chloroplumbagin, C-glycosylflavones- vitexin, isovitexin, orientin and isoorientin. The pattern of phenolics found supports affinity of Drosophyllum to the families-Droseraceae, Ancistrocladaceae and Dioncophyllaceae.