Constituents From Brazilian Propolis Against Edwardsiella ictaluri and Flavobacterium covae, Two Bacteria Affecting Channel Catfish (Ictalurus punctatus).

Edwardsiella ictaluri and Flavobacterium covae are two bacteria species that cause diseases in farm-raised channel catfish (Ictalurus punctatus) that cause heavy economic damage to the aquaculture industry, particularly to the channel catfish farming. In search for environmentally benign antibacterial compounds active against E. ictaluri and F. covae, we investigated the constituents isolated from Brazilian red, brown and green propolis. We have also synthetically modified active constituents to see if lipophilicity plays a role in enhancing antibacterial activities. Vestitol, neovestitol and methylvestitol were found to be the active constituents with minimum inhibitory concentration (MIC) relative to drug control florfenicol (RDCF) values (MIC-RDCF) of 7.6, 7.6 and 7.9 mg/L, respectively, against F. covae. The activity against E. ictaluri was not significant.

Characterization of the Phytotoxic Potential of Seven Copaifera spp. Essential Oils: Analyzing Active Compounds through Gas Chromatography-Mass Spectrometry Molecular Networking.

In recent years, there has been a need for environmentally friendly compounds for weed management in agriculture. This study is aimed to assess the phytotoxic constituents of oils obtained from oleoresins of seven Copaifera species (known as copaiba oils). Copaiba oils were separated from the resins by hydro-distillation, and the distillates were analyzed using gas chromatography-mass spectrometry (GC-MS) to characterize their chemical compositions. Multivariate analyses and molecular networking of GC-MS data were conducted to discern patterns in the chemical composition and phytotoxic activity of the oils, with the aim of identifying key compounds associated with phytotoxic activity. Seed germination bioassay revealed strong or complete germination inhibition against the monocot, Agrostis stolonifera but not the dicot Lactuca sativa. GC-MS analysis showed variations in composition among Copaifera species with some common compounds identified across multiple species. Caryophyllene oxide and junenol were associated with the observed phytotoxic effects. Automated flash chromatography was used to isolate the major compounds of the oils. Isolated compounds exhibited differing levels of phytotoxicity compared to the oils, suggesting the importance of interactions or synergism among oil components. These findings highlight the potential of copaiba oils as natural herbicidal agents and underscore the importance of considering species-specific responses in weed management strategies.

Larvicidal Activity of Constituents from the Main Brazilian Propolis Types: Green, Red, and Brown against Aedes aegypti.

In search of environmentally benign and mammalian-friendly mosquito-mitigating compounds, we conducted an investigation into the constituents isolated from Brazilian red, brown, and green propolis. Additionally, we synthetically modified active constituents to explore the role of lipophilicity in enhancing their larvicidal activity. Honeybees collect plant resins from their habitats, mix them with saliva, and utilize them to seal their beehives. The constituents present in propolis exhibit a unique composition specific to the geographical location and the fauna of the region. As part of the plant's natural defense mechanism, propolis compounds demonstrate antibacterial, insecticidal, and phytotoxic properties. Given that several insecticides target the enzyme acetylcholinesterase, we conducted in silico studies to examine the interactions between propolis compounds and acetylcholinesterase through molecular docking. In this study, we present the mosquito larvicidal activities of propolis constituents.

Pantoea ananatis, a plant growth stimulating bacterium, and its metabolites isolated from Hydrocotyle umbellata (dollarweed).

A bacterium growing on infected leaves of Hydrocotyle umbellata, commonly known as dollarweed, was isolated and identified as Pantoea ananatis. An ethyl acetate extract of tryptic soy broth (TSB) liquid culture filtrate of the bacterium was subjected to silica gel chromatography to isolate bioactive molecules. Indole was isolated as the major compound that gave a distinct, foul odor to the extract, together with phenethyl alcohol, phenol, tryptophol, N-acyl-homoserine lactone, 3-(methylthio)-1-propanol, cyclo(L-pro-L-tyr), and cyclo(dehydroAla-L-Leu). This is the first report of the isolation of cyclo(dehydroAla-L-Leu) from a Pantoea species. Even though tryptophol is an intermediate in the indoleacetic acid (IAA) pathway, we were unable to detect or isolate IAA. We investigated the effect of P. ananatis inoculum on the growth of plants. Treatment of Lemna paucicostata Hegelm plants with 4 × 109 colony forming units of P. ananatis stimulated their growth by ca. five-fold after 13 days. After 13 days of treatment, some control plants were browning, but treated plants were greener and no plants were browning. The growth of both Cucumis sativus (cucumber) and Sorghum bicolor (sorghum) plants was increased by ca. 20 to 40%, depending on the growth parameter and species, when the rhizosphere was treated with the bacterium after germination at the same concentration. Plant growth promotion by Pantoea ananatis could be due to the provision of the IAA precursor indole.

Larvicidal constituents from Poncirus trifoliata root extracts.

In the search for effective and environmentally friendly mosquito control agents, we have examined natural sources, such as microbes and plants, and the synthetic analogs of natural products. These plants and microbes have evolved in their ecological niches to produce defensive compounds against other competing organisms in their surroundings such as microbes, plants, and insects as a means to enhance their survival. Thus, some of these plants and microbes have bioactive compounds with insecticidal, fungicidal, and phytotoxic activities. In our previous research, we successfully isolated bioactive constituents from natural sources. We have carried out synthetic modifications and total synthesis of marginally active isolated compounds to achieve significantly higher active compounds. We have focused on plants in the Rutaceae family as the members of this family are known to possess bioactive compounds with algicidal, antifungal, insecticidal, and fungicidal activities. In this article, we report the isolation and structure elucidation of mosquito larvicidal constituents from Poncirus trifoliata (Rutaceae) root extract.

Characterization of Toxicological and Neurophysiological Effects of Natural Product Based Chromenes to Fall Armyworm, Spodoptera frugiperda.

We previously extracted and purified a chromene amide from Amyris texana and found this scaffold is moderately insecticidal and thus, this study aimed to test the insecticidal properties of 13 synthetically derived chromene analogs to the fall armyworm (FAW, Spodoptera frugiperda). Microinjection of chromenes with alcohol or aldehydes substitutions at the meta position on the benzopyran moiety led to moderate toxicity that was approximately 2- to 3-fold less toxic when compared to permethrin, yet microinjection of differently substituted chromenes exhibited little to no toxicity. Similarly, chromenes with alcohol or aldehydes substitutions at the meta position on the benzopyran moiety were among the most toxic chromenes studied through ingested exposure. In addition to acute toxicity, select chromenes significantly increased the percentage of developmental defects upon eclosion that prevented adult moths from being capable of flight, suggesting these compounds alter development. Interestingly, microinjection yielded differing signs of intoxication between alcohol and aldehyde substitutions where the alcohol resulted in flaccid paralysis and lethargy whereas aldehyde led to tonic contractions and hyperactivity. These contrasting signs of intoxication were also observed in electrophysiological assays where alcohol substitutions led to the depression of central neuron firing activity and aldehyde substitutions led to hyperexcitation of central neurons. In summary, the chromene amides led to acute lethality and/or altered developmental trajectories of FAW, yet the high doses required for acute mortality suggest these scaffolds hold relatively little promise for development into FAW-directed insecticides but may represent novel growth regulators for FAW.

Microbial transformation of some simple isoquinoline and benzylisoquinoline alkaloids and in vitro studies of their metabolites.

Simple isoquinoline alkaloids (heliamine, dehydroheliamine), a phthalide isoquinoline alkaloid noscapine, and an aporphine alkaloid boldine are biosynthetically derived from an amino acid tyrosine. These substrates and a simple synthetic isoquinoline alkaloid (2-acetyl-7-amino-1,2,3,4-tetrahydroisoquinoline) contain an isoquinoline nucleus. The biotransformation of these substrates via reduction, oxidation, hydroxylation, and N-oxidation reactions with different microorganism produced nine metabolites, namely: N-(2-acetyl-1,2,3,4-tetrahydroisoquinolin-7-yl) acetamide (Metabolite 1), heliamine N-oxide (Metabolite 2), 6,7-dimethoxyisoquinoline (Metabolite 3), 3,4-dihydro-6,7-dimethoxy isoquinolin-1-one (Metabolite 4), heliamine (Metabolite 5), dehydroheliamine N-oxide (Metabolite 6), cotarnine (Metabolite 7), 5-hydroxy cotarnine (Metabolite 8), and boldine N-oxide (Metabolite 9). Primarily, the metabolites are structurally elucidated by one-dimensional (1D) and two-dimensional (2D) nuclear magnetic resonance (NMR) analyses, and high-resolution electrospray ionization mass spectrometry (HR-ESIMS). Furthermore, the substrates and their isolated metabolites are evaluated in vitro for their anti-inflammatory, antimicrobial, cytotoxicity, and anticancer activities. The in vitro studies reveal that some of the isolated compounds are potential as anti-inflammatory, antitumor, and antimicrobial leads.

In silico and in vitro studies of isolated constituents from Callistemon citrinus leaves: Anti-microbial potential and inhibition of iNOS activity.

Phytochemical investigation of Callistemon citrinus (Curtis) Skeels (syn. Callistemon lanceolatus (Sm.) Sweet and Melaleuca citrina (Curtis) Dum.Cours.) leaves resulted in the isolation of five undescribed compounds, including one acylphloroglucinol derivative and four monoterpene galloylglucosides, in addition to 29 known diverse secondary metabolites. Interestingly, this study reports chemosystematically significant isolation of the monoterpene galloylglucosides from the genus for the first time. Furthermore, exploration of the isolated compounds as inhibitors of inflammation-related molecular targets, molecular docking studies targeting human adipocyte lipid-binding protein FABP4 (3P6H) and human nitric oxide synthase (3E7G) were carried out in order with the in vitro evaluation of the isolated compounds for their anti-microbial and inhibitory of inducible nitric oxide synthase (iNOS) activities. Molecular docking studies revealed that eighteen compounds showed lower docking scores than ibuprofen, the native ligand in the crystal structure 3P6H, and nine compounds showed lower docking scores than AR-C95791, the native ligand in the binding site of 3E7G. Additionally, in vitro studies revealed that seven compounds showed moderate iNOS inhibitory activity. They also were moderately cytotoxic to HepG2, LLC-PK1 and Vero cells. Pulverulentone A showed moderate antibacterial activity against MRSA (IC50 22.2 µM) and antifungal activity against C. neoformans, while corosolic acid showed strong antibacterial activity against VRE (IC50 15.9 µM).Thus, the in silico and in vitro studies indicated that some isolated compounds hold potentials as inhibitors of iNOS activity and anti-microbial agents.

Furanocoumarin with Phytotoxic Activity from the Leaves of Amyris elemifera (Rutaceae).

Bioassay-guided fractionation of the ethyl acetate extract of Amyris elemifera leaves was carried out to identify phytotoxic and antifungal constituents. A novel phytotoxic furanocoumarin 8-(3-methylbut-2-enyloxy)-marmesin acetate (1) and its deacyl analog 8-(3-methylbut-2-enyloxy)-marmesin (2) were isolated. The X-ray crystal structure determination is reported for the first time for 1. Both 1 and 2 have the S configuration at C-2' based on X-ray crystallographic data. Both these compounds inhibited the growth of the dicot Lactuca sativa (lettuce) and the monocot Agrostis stolonifera with a more pronounced inhibitory effect on the monocots at 330 µM by 1. In Lemna paucicostata Hegelm phytotoxicity bioassay, the IC50 value for 1 was 26 µM, whereas 2 had an IC50 value of 102 µM. Compounds 1 and 2 were weakly antifungal against Colletotrichum fragariae Brooks in TLC bioautography.

Antibacterial Activity of Constituents from Mangosteen Garcinia mangostana Fruit Pericarp against Several Channel Catfish Pathogens.

Bacterial diseases cause major financial damage to the producers of Channel Catfish Ictalurus punctatus in the southeastern USA. The two most common bacterial diseases among pond-raised Channel Catfish are enteric septicemia of catfish, caused by the gram-negative bacterium Edwardsiella ictaluri, and columnaris disease, caused by the rod-shaped, gram-negative bacterium Flavobacterium columnare. Streptococcosis is another, less-common bacterial disease in catfish and is caused by the gram-positive coccus Streptococcus iniae. Catfish farmers typically rely on commercial antibiotics and other chemicals to prevent the economic damage from these diseases. Environmentally benign and efficacious alternatives to the currently used antibiotics and chemicals will tremendously help the catfish aquaculture industry. As part of our ongoing efforts in the search for such novel compounds, we investigated ethyl acetate and methanol extracts of mangosteen Garcinia mangostana fruit pericarp via bioassay-guided fractionation. Gamma-mangostin (γ-mangostin) was isolated and identified as the most promising active metabolite against F. columnare. One of the constituents in the mangosteen fruit pericarp, alpha-mangostin (α-mangostin), is the major xanthone; α-mangostin was found to be 10-fold less active than γ-mangostin when minimum inhibitory concentration values were compared.

Mosquitocidal Activity of a Naturally Occurring Isochroman and Synthetic Analogs from the Plant Pathogenic Fungus, Diaporthe eres Against Aedes aegypti (Diptera: Culicidae).

The culture filtrate of a plant pathogenic fungus that infects English ivy (Hedera helix L., Araliaceae) was investigated for mosquitocidal constituents by bioassay-guided isolation. The fungus responsible for pathogenic effects on the plant H. helix has been identified as Diaporthe eres Nitschke by molecular techniques. The mosquito adulticidal constituent in the culture filtrate was identified as 3,4-dihydro-8-hydroxy-3,5-dimethylisocoumarin (1) by spectroscopic techniques. Laboratory bioassays showed that (1) had larvicidal activity against permethrin-susceptible and -resistant Aedes aegypti strains. This compound was not active as an adulticide when tested by topical bioassay. Several analogs of (1) were synthesized and had better mosquitocidal activities than the naturally occurring (1) constituent.

Isolation of a phytotoxic isocoumarin from Diaporthe eres-infected Hedera helix (English ivy) and synthesis of its phytotoxic analogs.

BACKGROUND: The fungus Diaporthe eres was isolated from a fungal pathogen-infected leaf of Hedera helix (English ivy) exhibiting necrosis. It is hypothesized that the causative fungus produces phytotoxins as evidenced by necrotic lesions on the leaves. RESULTS: The fungus was isolated and grown in Czapek Dox broth culture medium and potato dextrose broth culture medium and identified as Diaporthe eres. The ethyl acetate extracts of the culture broths were phytotoxic to lettuce (Lactuca sativa) and bentgrass (Agrostis stolonifera). 3,4-Dihydro-8-hydroxy-3,5-dimethylisocoumarin (1) and tyrosol (2) were isolated and identified as the phytotoxic constituents. Six analogs of 3,4-dihydro-isocoumarin were synthesized and shown to be phytotoxic. The synthesized 3,4-dihydro-8-hydroxy-3,7-dimethylisocoumarin and 3,4-dihydro-8-hydroxy-3,3,7-trimethylisocoumarin were two- to three-fold more phytotoxic than the naturally occurring 1 in a Lemna paucicostata growth bioassay. CONCLUSION: Synthesis and herbicidal activities of the several new analogs of 1 are reported for the first time. These promising molecules should be used as templates for synthesis and testing of more analogs. © 2017 Society of Chemical Industry.

Khellin and Visnagin, Furanochromones from Ammi visnaga (L.) Lam., as Potential Bioherbicides.

Plants constitute a source of novel phytotoxic compounds to be explored in searching for effective and environmentally safe herbicides. From a previous screening of plant extracts for their phytotoxicity, a dichloromethane extract of Ammi visnaga (L.) Lam. was selected for further study. Phytotoxicity-guided fractionation of this extract yielded two furanochromones, khellin and visnagin, for which herbicidal activity had not been described before. Khellin and visnagin were phytotoxic to model species lettuce (Lactuca sativa) and duckweed (Lemna paucicostata), with IC50 values ranging from 110 to 175 µM. These compounds also inhibited the growth and germination of a diverse group of weeds at 0.5 and 1 mM. These weeds included five grasses [ryegrass (Lolium multiflorum), barnyardgrass (Echinocloa crus-galli), crabgrass (Digitaria sanguinalis), foxtail (Setaria italica), and millet (Panicum sp.)] and two broadleaf species [morningglory (Ipomea sp.) and velvetleaf (Abutilon theophrasti)]. During greenhouse studies visnagin was the most active and showed significant contact postemergence herbicidal activity on velvetleaf and crabgrass at 2 kg active ingredient (ai) ha-1. Moreover, its effect at 4 kg ai ha-1 was comparable to the bioherbicide pelargonic acid at the same rate. The mode of action of khellin and visnagin was not a light-dependent process. Both compounds caused membrane destabilization, photosynthetic efficiency reduction, inhibition of cell division, and cell death. These results support the potential of visnagin and, possibly, khellin as bioherbicides or lead molecules for the development of new herbicides.

Larvicidal and Adulticidal Activity of Chroman and Chromene Analogues against Susceptible and Permethrin-Resistant Mosquito Strains.

Mosquitoes play a major role as vectors that transmit parasitic and viral diseases worldwide, especially in tropical and subtropical countries. Mosquito borne diseases not only affect humans but they also affect livestock in many parts of the world. They carry diseases that are lethal to dogs and horses. Dog heartworm disease (Dirofilaria immitis) is a parasitic disease spread through mosquitoes. This disease is not limited to dogs, but it can affect other animals and humans as well. Eastern equine encephalitis (EEE) and West Nile virus (WNV) are also mosquito borne diseases that affect the central nervous system of horses and cause severe complications and death. Emergence of resistance among mosquitoes to current pesticides has increased the importance of the search for alternate compounds that are effective and environmentally benign with diverse modes of actions than those that are commercially available. Aedes aegypti mosquitoes are the primary vector for transmission of Zika viral fever, yellow fever, dengue fever, and chikungunya. Mosquito control is currently the best strategy to prevent mosquito borne diseases. There are numerous approaches for control of potentially dangerous mosquito populations. These approaches include the use of adulticides (insecticides), larvicides, and, to a limited extent, the use of repellents. Our previous studies have shown the mosquito repellent activity of chromenes. In the present study, we demonstrate larvicidal and adulticidal activity of chroman and chromene analogues against a permethrin susceptible laboratory strain as well as activity against a permethrin-resistant strain of Aedes aegypti.

Phomalactone from a Phytopathogenic Fungus Infecting ZINNIA elegans (ASTERACEAE) Leaves.

Zinnia elegans Jacq. plants are infected by a fungus that causes dark red spots with necrosis on leaves, particularly in late spring to the middle of summer in the Mid-South of the United States. This fungal disease causes the leaves to wilt and eventually kills the plant. The fungus was isolated, cultured in potato dextrose broth, and identified as Nigrospora sphaerica by molecular techniques. Two major lactone metabolites (phomalactone and catenioblin A) were isolated from liquid culture of N. sphaerica isolated from Z. elegans. When injected into leaves of Z. elegans, phomalactone caused lesions similar to those of the fungus. The lesion sizes were proportional to the concentration of the phomalactone. Phomalactone, but not catenioblin A, was phytotoxic to Z. elegans and other plant species by inhibition of seedling growth and by causing electrolyte leakage from photosynthetic tissues of both Z. elegans leaves and cucumber cotyledons. This latter effect may be related to the wilting caused by the fungus in mature Z. elegans plants. Phomalactone was moderately fungicidal to Coletotrichum fragariae and two Phomopsis species, indicating that the compound may keep certain other fungi from encroaching into plant tissue that N. sphaerica has infected. Production of large amounts of phomalactone by N. sphaerica contributes to the pathogenic behavior of this fungus, and may have other ecological functions in the interaction of N. sphaerica with other fungi. This is the first report of isolation of catenioblin A from a plant pathogenic fungus. The function of catenioblin A is unclear, as it was neither significantly phyto- nor fungitoxic.

Mosquito repellents based on a natural chromene analogue with longer duration of action than N,N-diethyl-meta-toluamide (DEET).

Mosquito repellents play a major role in reducing bites and therefore mitigating transmission of mosquito-borne diseases. There is concern by some about the reported neurotoxic effects of the popular repellent DEET. Also, a product with longer effective activity after application is needed. This paper describes the synthesis and repellent activity of (2,2 dimethyl-2H-chromen-5-yl)methanol, a derivative of chromene amide that is a compound from the plant Amyris texana . This compound is more potent and provides longer duration of protection than DEET against Aedes aegypti (L.), the primary vector that transmits pathogens causing yellow and dengue fevers in humans.

Natural-product-based chromenes as a novel class of potential termiticides.

BACKGROUND: Among the termite infestations in the United States, the Formosan subterranean termite, Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae), is considered to be the most devastating termite pest. This pest most likely invaded North America as a result of the disembarkation of wooden military cargo at the port of New Orleans that arrived from Asia during and after World War II. It has now spread over other states, including Texas, Florida, South Carolina and California. Devastation caused by C. formosanus in North America has been estimated to cost $ US 1 billion a year. Over the past decades, organochlorines and organophosphates, the two prominent classes of termite control agents, have been banned owing to environmental and human health concerns. At the present time, phenylpyrazoles, pyrethroids, chloronicotinyls and pyrroles are being used as termite control agents. Mammalian toxicity and seeping of these compounds into groundwater are some of the drawbacks associated with these treatments. The instruction for the application of these termiticides indicate ground water advisory. Hence, with the increasing spread of termite infestation there is an increased need to discover effective, environmentally friendly and safe termite control agents with minimal mammalian toxicity. RESULTS: Chromene analogs derived from a natural-product-based chromene amide isolated from Amyris texana were tested in a collaborative discovery program for effective, environmentally friendly termite control agents. Several chromene derivatives were synthesized and characterized as a novel class of potential termiticides, followed by bioassays. These compounds exhibited significantly higher mortalities compared with untreated controls in laboratory bioassays. CONCLUSION: Chromene derivatives have been shown to be a potential novel class of termiticides against Formosan subterranean termites.

New class of algicidal compounds and fungicidal activities derived from a chromene amide of Amyris texana.

A chromene amide, N-[2-(2,2-dimethyl-2H-1-benzopyran-6-yl)ethyl]-N,3-dimethylbutanamide, was isolated from the EtOAc extract of the leaves of Amyris texana and found to have moderate antifungal activity against Colletotrichum spp. and selective algicidal activity against Planktothrix perornata, a cyanobacterium (blue-green alga) that causes musty off-flavor in farm-raised channel catfish (Ictalurus punctatus). To improve the selective algicidal activity and provide water solubility, a series of chromene analogues were synthesized and evaluated for algicidal activity using a 96-well microplate rapid bioassay. In addition, the chromene analogues were evaluated for antifungal and phytotoxic activities. Hydrochloride salts of a chromene amine analogue showed improved water solubility and selectivity toward P. perornata with activity comparable to that of the naturally occurring chromene amide.

Managing earthworm casts (Oligochaeta: Lumbricidae) in turfgrass using a natural byproduct of tea oil (Camellia sp.) manufacture.

BACKGROUND: Earthworm casts are a worldwide problem on golf courses and sports fields when they disrupt the playability, aesthetics and maintenance of closely mowed playing surfaces. Currently, no pesticides are labeled for earthworms in the United States. Tea seed pellets (TSPs), a saponin-rich byproduct of Camellia oleifera Abel oil manufacture, were tested for expelling earthworms and reducing casts on creeping bentgrass turf. The fate of expelled worms, methods for removing them and impacts on pest and beneficial arthropods were also evaluated. RESULTS: Application of TSPs at 2.93 kg 100 m(-2), followed by irrigation, quickly expelled earthworms from the soil. A single application reduced casts by 80-95% for at least 5 weeks. Mowing or sweeping removed expelled earthworms from putting green surfaces. Most expelled earthworms burrowed down when transferred to untreated turf, but few survived. Bioassay-guided fractionation confirmed the vermicidal activity results from a mix of saponins. TSPs did not reduce the abundance of beneficial soil arthropods, nor did they control black cutworms or white grubs in treated turf. CONCLUSION: TSPs are an effective botanical vermicide that could be useful for selectively managing earthworm casts on closely mowed turfgrass. They might also be used to suppress earthworms in grassy strips alongside runways to reduce bird strike hazard at airports.

Natural toxins for use in pest management.

Natural toxins are a source of new chemical classes of pesticides, as well as environmentally and toxicologically safer molecules than many of the currently used pesticides. Furthermore, they often have molecular target sites that are not exploited by currently marketed pesticides. There are highly successful products based on natural compounds in the major pesticide classes. These include the herbicide glufosinate (synthetic phosphinothricin), the spinosad insecticides, and the strobilurin fungicides. These and other examples of currently marketed natural product-based pesticides, as well as natural toxins that show promise as pesticides from our own research are discussed.