Nanosuspension of quercetin: preparation, characterization and effects against Aedes aegypti larvae

Termiticidal, biochemical, and morpho-histological effects of botanical based nanoemulsion against a subterranean termite, Odontotermes Formosanus Shiraki

Recently, the use of nanopesticides has shown significant efficacy in the control of many pests. However, the effect of nanopesticides, especially nanoemulsions, on suppressing termites, Odontotermes formosanus (Shiraki, 1909) (O. formosanus), has not been studied yet. Therefore, this study aimed to produce nanoemulsions of the essential oils of eucalyptus (Eucalyptus globulus Labill; E-EO) and nutmeg (Myristica fragrans Houtt; N-EO) to suppress O. formosanus. The analysis of eucalyptus nanoemulsion (E-NE) and nutmeg nanoemulsion (N-NE) was confirmed by using UV-Vis, dynamic light scattering, zeta potential, transmission electron microscopy, scanning electron microscopy, and energy dispersive spectroscopy. In addition, chemical analysis by Gas Chromatography with a mass spectrometer (GC-MS) exhibited the major constituents of E-NE and N-NE. The principal chemical components of E-NE included D-limonene, eucalyptol, 1,5-cyclooctadiene,3,4-dimethyl, benzene, and 1-methyl-3-(1 methylethyl)-, while the main constituents in N-NE were cyclohexane,1-methylene-4-(1 methylethenyl)-, eucalyptol, and L-. alpha. -terpineol. The mortality rates were 100% and 99.53%, respectively, after 24 hours of treatment with a concentration of 140 mg/mL, compared to 23.43% and 43.55%, respectively, from E-EO and N-EO treatment. These results refer to the essential oils' nanoemulsion as far more effective than the essential oils themselves. Furthermore, the effects of E-NE and N-NE on detoxification enzymes such as acetylcholinesterase, carboxylesterase, acid and alkaline phosphatase were investigated, as well as total protein concentrations, and the results have been found to be significantly increasing or decreasing in comparison with control. Besides, histological and morphological alterations found post exposure to E-NE and N-NE were shown. Overall, the results from this study clearly indicate that the nanopesticide-formulated nanoemulsions may have great potential to be used as novel, environmentally safe insecticides for controlling O. formosanus.

Nano Drug Delivery Strategies for an Oral Bioenhanced Quercetin Formulation

Quercetin, a naturally occurring flavonoid, has been credited with a wide spectrum of therapeutic properties. However, the oral use of quercetin is limited due to its poor water solubility, low bioavailability, rapid metabolism, and rapid plasma clearance. Quercetin has been studied extensively when used with various nanodelivery systems for enhancing quercetin bioavailability. To enhance its oral bioavailability and efficacy, various quercetin-loaded nanosystems such as nanosuspensions, polymer nanoparticles, metal nanoparticles, emulsions, liposomes or phytosomes, micelles, solid lipid nanoparticles, and other lipid-based nanoparticles have been investigated in in-vitro cells, in-vivo animal models, and humans. Among the aforementioned nanosystems, quercetin phytosomes are attracting more interest and are available on the market. The present review covers insights into the possibilities of harnessing quercetin for several therapeutic applications and a special focus on anticancer applications and the clinical benefits of nanoquercetin formulations.

Particle Size Tailoring of Quercetin Nanosuspensions by Wet Media Milling Technique: A Study on Processing and Formulation Parameters

Background

A large number of new substances have insufficient biopharmaceutical properties for oral administration caused by their slow dissolution rate and poor solubility.

Objective

The purpose of our experiment was to improve the physicochemical properties of a hydrophobic drug, quercetin, by the nanomilling approach.

Methods

Quercetin nanosuspensions were prepared using a wet-milling method followed by lyophilization. Stabilizer type and ratio, drug content, milling time, and bead size were identified as critical variables, and their impacts on quercetin particle size were assessed. The optimized nanocrystal was characterized by its morphology, crystallinity, molecular interactions, saturation solubility, and dissolution properties.

Results

At optimized process conditions of milling at 500 rpm for 18 cycles of grinding with 0.3 - 0.4 mm zirconium oxide beads, minimum particle size, and PDI values were 281.21 nm and 0.22, respectively. Nanocrystals showed rod-like nanostructures, and XRD scans confirmed a decrease in drug crystallinity. The optimized formulation showed increased solubility and dissolution rate, as well as good physical stability.

Conclusions

Particle size reduction by media milling technique was an efficient method for the solubility enhancement of hydrophobic drugs.

Methanolic Extracts of Chiococca alba in Aedes aegypti Biorational Management: Larvicidal and Repellent Potential, and Selectivity against Non-Target Organisms

The use of formulations containing botanical products for controlling insects that vector human and animal diseases has increased in recent years. Plant extracts seem to offer fewer risks to the environment and to human health without reducing the application strategy's efficacy when compared to synthetic and conventional insecticides and repellents. Here, we evaluated the potential of extracts obtained from caninana, Chiococca alba (L.) Hitchc. (Rubiaceae), plants as a tool to be integrated into the management of Aedes aegypti, one of the principal vectors for the transmission of arborviruses in humans. We assessed the larvicidal and repellence performance against adult mosquitoes and evaluated the potential undesired effects of the extracts on non-target organisms. We assessed the susceptibility and predatory abilities of the nymphs of Belostoma anurum, a naturally occurring mosquito larva predator, and evaluated the C. alba extract's cytotoxic effects in mammalian cell lines. Our chromatographic analysis revealed 18 compounds, including rutin, naringin, myricetin, morin, and quercetin. The methanolic extracts of C. alba showed larvicidal (LC₅₀ = 82 (72-94) mg/mL) activity without killing or affecting the abilities of B. anurum to prey upon mosquito larvae. Our in silico predictions revealed the molecular interactions between rutin and the AeagOBP1 receptor to be one possible mechanism for the repellent potential recorded for formulations containing C. alba extracts. Low cytotoxicity against mammalian cell lines reinforces the selectivity of C. alba extracts. Collectively, our findings highlight the potential of C. alba and one of its constituents (rutin) as alternative tools to be integrated into the management of A. aegypti mosquitoes.

Anti-Inflammatory, Antioxidative, and Nitric Oxide-Scavenging Activities of a Quercetin Nanosuspension with Polyethylene Glycol in LPS-Induced RAW 264.7 Macrophages

Quercetin (Qu) is a dietary antioxidant and a member of flavonoids in the plant polyphenol family. Qu has a high ability to scavenge reactive oxygen species (ROS) and reactive nitrogen species (RNS) molecules; hence, exhibiting beneficial effects in preventing obesity, diabetes, cancer, cardiovascular diseases, and inflammation. However, quercetin has low bioavailability due to poor water solubility, low absorption, and rapid excretion from the body. To address these issues, the usage of Qu nanosuspensions can improve physical stability, solubility, and pharmacokinetics. Therefore, we developed a Qu and polyethylene glycol nanosuspension (Qu-PEG NS) and confirmed its interaction by Fourier transform infrared analysis. Qu-PEG NS did not show cytotoxicity to HaCaT and RAW 264.7 cells. Furthermore, Qu-PEG NS effectively reduced the nitrogen oxide (NO) production in lipopolysaccharide (LPS)-induced inflammatory RAW 264.7 cells. Additionally, Qu-PEG NS effectively lowered the levels of COX-2, NF-κB p65, and IL-1β in the LPS-induced inflammatory RAW 264.7 cells. Specifically, Qu-PEG NS exhibited anti-inflammatory properties by scavenging the ROS and RNS and mediated the inhibition of NF-κB signaling pathways. In addition, Qu-PEG NS had a high antioxidant effect and antibacterial activity against Escherichia coli and Bacillus cereus. Therefore, the developed novel nanosuspension showed comparable antioxidant, anti-inflammatory, and antibacterial functions and may also improve solubility and physical stability compared to raw quercetin.

Larvicidal formulation containing N-tosylindole: A viable alternative to chemical control of Aedes aegypti

Aedes aegypti is currently a major public health problem. This mosquito is responsible for the spread of infectious diseases that have been causing epidemics worldwide. Surfactant-stabilized systems, such as microemulsions, liquid-crystalline precursors and liquid crystals, are promising sustained delivery formulations of hydrophilic and hydrophobic substances. These systems are biocompatible water-soluble reservoirs for N-tosylindole exhibiting biological activity against Aedes aegypti Linn. (Diptera: Culicidae) larvae. The ternary diagram displayed four regions: microemulsion (ME), liquid crystal (LC), emulsion (EM) and phase separation (PS). PLM and SAXS distinguished microemulsions, lamellar and hexagonal phase liquid crystals. The system had a lethal concentration of 50% (LC₅₀ = 0.1 ppm, 0.36 µM) lower than pure N-tosylindole (0.24 ppm, 0.88 µM), which has limitations in aqueous media. Furthermore, the formulation displayed no toxicity to Artemia sp., a non-target organism. The system exhibited excellent larvicidal activity as an alternative to commercial larvicides that have shown resistance and toxicity to the environment by Ae. aegypti larvae due to prolonged use. In addition, a two-fold increase in potency was observed.

HPLC-DAD analysis and antimicrobial activities of Spondias mombin L. (Anacardiaceae)

Spondias mombin is used in the folk medicine for the treatment of diarrhea and dysentery, indicating that extracts obtained from this species may present pharmacological activities against pathogenic microorganisms. The purpose of this work was to investigate the chemical composition and evaluate the antimicrobial activity of extracts obtained from the leaves (aqueous) and bark (hydroethanolic) of S. mombin both as single treatments and in combination with conventional drugs. Following a qualitative chemical prospection, the extracts were analyzed by HPLC-DAD. The antimicrobial activities were evaluated by microdilution. The combined activity of drugs and extracts was verified by adding a subinhibitory concentration of the extract in the presence of variable drug concentrations. The Minimum Fungicidal Concentration (MFC) was determined by a subculture of the microdilution test, while the effect of the in vitro treatments on morphological transition was analyzed by subculture in moist chambers. While the qualitative analysis detected the presence of phenols and flavonoids, the HPLC analysis identified quercetin, caffeic acid, and catechin as major components in the leaf extract, whereas kaempferol and quercetin were found as major compounds in the bark extract. The extracts showed effective antibacterial activities only against the Gram-negative strains. With regard to the combined activity, the leaf extract potentiated the action of gentamicin and imipenem (against Staphylococcus aureus), while the bark extract potentiated the effect of norfloxacin (against S. aureus), imipenem (against Escherichia coli), and norfloxacin (against Pseudomonas aeruginosa). A more significant antifungal (fungistatic) effect was achieved with the bark extract (even though at high concentrations), which further enhanced the activity of fluconazole. The extracts also inhibited the emission of filaments by Candida albicans and Candida tropicalis. Together, these findings suggest that that the extract constituents may act by favoring the permeability of microbial cells to conventional drugs, as well as by affecting virulence mechanisms in Candida strains.

Molecular action of larvicidal flavonoids on ecdysteroidogenic glutathione S-transferase Noppera-bo in Aedes aegypti

Background

Mosquito control is a crucial global issue for protecting the human community from mosquito-borne diseases. There is an urgent need for the development of selective and safe reagents for mosquito control. Flavonoids, a group of chemical substances with variable phenolic structures, such as daidzein, have been suggested as potential mosquito larvicides with less risk to the environment. However, the mode of mosquito larvicidal action of flavonoids has not been elucidated.

Results

Here, we report that several flavonoids, including daidzein, inhibit the activity of glutathione S-transferase Noppera-bo (Nobo), an enzyme used for the biosynthesis of the insect steroid hormone ecdysone, in the yellow fever mosquito Aedes aegypti. The crystal structure of the Nobo protein of Ae. aegypti (AeNobo) complexed with the flavonoids and its molecular dynamics simulation revealed that Glu113 forms a hydrogen bond with the flavonoid inhibitors. Consistent with this observation, substitution of Glu113 with Ala drastically reduced the inhibitory activity of the flavonoids against AeNobo. Among the identified flavonoid-type inhibitors, desmethylglycitein (4′,6,7-trihydroxyisoflavone) exhibited the highest inhibitory activity in vitro. Moreover, the inhibitory activities of the flavonoids correlated with the larvicidal activity, as desmethylglycitein suppressed Ae. aegypti larval development more efficiently than daidzein.

Conclusion

Our study demonstrates the mode of action of flavonoids on the Ae. aegypti Nobo protein at the atomic, enzymatic, and organismal levels.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12915-022-01233-2.

Herbal nanomedicines: Recent advancements, challenges, opportunities and regulatory overview

BACKGROUND

Herbal Nano Medicines (HNMs) are nano-sized medicine containing herbal drugs as extracts, enriched fractions or biomarker constituents. HNMs have certain advantages because of their increased bioavailability and reduced toxicities. There are very few literature reports that address the common challenges of herbal nanoformulations, such as selecting the type/class of nanoformulation for an extract or a phytochemical, selection and optimisation of preparation method and physicochemical parameters. Although researchers have shown more interest in this field in the last decade, there is still an urgent need for systematic analysis of HNMs.

PURPOSE

This review aims to provide the recent advancement in various herbal nanomedicines like polymeric herbal nanoparticles, solid lipid nanoparticles, phytosomes, nano-micelles, self-nano emulsifying drug delivery system, nanofibers, liposomes, dendrimers, ethosomes, nanoemulsion, nanosuspension, and carbon nanotube; their evaluation parameters, challenges, and opportunities. Additionally, regulatory aspects and future perspectives of herbal nanomedicines are also being covered to some extent.

METHODS

The scientific data provided in this review article are retrieved by a thorough analysis of numerous research and review articles, textbooks, and patents searched using the electronic search tools like Sci-Finder, ScienceDirect, PubMed, Elsevier, Google Scholar, ACS, Medline Plus and Web of Science.

RESULTS

In this review, the authors suggested the suitability of nanoformulation for a particular type of extracts or enriched fraction of phytoconstituents based on their solubility and permeability profile (similar to the BCS class of drugs). This review focuses on different strategies for optimising preparation methods for various HNMs to ensure reproducibility in context with all the physicochemical parameters like particle size, surface area, zeta potential, polydispersity index, entrapment efficiency, drug loading, and drug release, along with the consistent therapeutic index.

CONCLUSION

A combination of herbal medicine with nanotechnology can be an essential tool for the advancement of herbal medicine research with enhanced bioavailability and fewer toxicities. Despite the challenges related to traditional medicine's safe and effective use, there is huge scope for nanotechnology-based herbal medicines. Overall, it is well stabilized that herbal nanomedicines are safer, have higher bioavailability, and have enhanced therapeutic value than conventional herbal and synthetic drugs.

Challenges, Advances and Opportunities in Exploring Natural Products to Control Arboviral Disease Vectors

Natural products constitute an important source of molecules for product development. However, despite numerous reports of compounds and active extracts from biodiversity, poor and developing countries continue to suffer with endemic diseases caused by arboviral vectors, including dengue, Zika, chikungunya and urban yellow fever. Vector control remains the most efficient disease prevention strategy. Wide and prolonged use of insecticides has resulted in vector resistance, making the search for new chemical prototypes imperative. Considering the potential of natural products chemistry for developing natural products-based products, including insecticides, this contribution discusses the general aspects and specific characteristics involved in the development of drug leads for vector control. Throughout this work, we highlight the obstacles that need to be overcome in order for natural products compounds to be considered promising prototypes. Moreover, we analyze the bottlenecks that should be addressed, together with potential strategies, to rationalize and improve the efficiency of the drug discovery process.

The Promising Role of Chitosan-Poloxamer 188 Nanocrystals in Improving Diosmin Dissolution and Therapeutic Efficacy against Ferrous Sulfate-Induced Hepatic Injury in Rats

Diosmin (DSN) exhibits poor water solubility and low bioavailability. Although nanocrystals (NCs) are successful for improving drug solubility, they may undergo crystal growth. Therefore, DSN NCs were prepared, employing sonoprecipitation utilizing different stabilizers. The optimum stabilizer was combined with chitosan (CS) as an electrostatic stabilizer. NCs based on 0.15% w/v poloxamer 188 (PLX188) as a steric stabilizer and 0.04% w/v CS were selected because they showed the smallest diameter (368.93 ± 0.47 nm) and the highest ζ-potential (+40.43 ± 0.15 mV). Mannitol (1% w/v) hindered NC enlargement on lyophilization. FT-IR negated the chemical interaction of NC components. DSC and XRD were performed to verify the crystalline state. DSN dissolution enhancement was attributed to the nanometric rod-shaped NCs, the high surface area, and the improved wettability. CS insolubility and its diffusion layer may explain controlled DSN release from CS-PLX188 NCs. CS-PLX188 NCs were more stable than PLX188 NCs, suggesting the significance of the combined electrostatic and steric stabilization strategies. The superiority of CS-PLX188 NCs was indicated by the significantly regulated biomarkers, pathological alterations, and inducible nitric oxide synthase (iNOS) expression of the hepatic tissue compared to DSN suspension and PLX188 NCs. Permeation, mucoadhesion, and cellular uptake enhancement by CS may explain this superiority.

Combining chemometric and phytochemical tools to isolate and characterize activity of Vismia gracilis compounds against Aedes aegypti

Vismia gracilis extracts were tested against Aedes aegypti to assess mortality and behavioural effects. The leaf hexanic extract (L-Hex) presented increased larvicidal activity with exposure period: LC₅₀ 46.48 µg/mL (24 h) and LC₅₀ 20.57 µg/mL (48 h). Eight compounds were annotated/isolated from the L-Hex active extract, 4 benzophenones and 4 anthraquinones. Considering chemometric findings, the benzophenone moiety, tested as the commercial benzophenone, promoted larval mortality (LC₅₀ 16.35 µg/mL). Both the L-Hex extract and benzophenone induced intestinal damage in larvae. Benzophenone also promoted toxicity and behavioural effects in female adults. These findings highlighted the potential use of this class of compounds for developing vector-control products.

Hydroalcoholic extract of Caryocar brasiliense Cambess. leaves affect the development of Aedes aegypti mosquitoes

INTRODUCTION:

Curtailing the development of the aquatic immature stages of Aedes aegypti is one of the main measures to limit their spread and the diseases transmitted by them. The use of plant extracts is a promising approach in the development of natural insecticides. Thus, this research aimed to characterize the inhibitory effect of the hydroalcoholic extract of Caryocar brasiliense leaves on the emergence of adult A. aegypti and the main substances that constitute this extract.

METHODS:

C. brasiliense leaf extract was prepared by ethanol (70%) extraction. Bioassays using L3 larvae were performed at concentrations of 200, 300, 400, and 500 ppm. We identified the major secondary metabolites present in this extract, and performed toxicity tests on an off-target organism, Danio rerio.

RESULTS:

We observed a significant delay in the development of A. aegypti larvae mainly at a concentration of 500 ppm, and estimated an emergence inhibition for 50% of the population of 150 ppm. Moreover, the C. brasiliense leaf extracts exhibited low toxicity in D. rerio. The main compounds found in the extract were quercetin, violaxanthin, myricetin3-O-hexoside, methyl-elagic-3-arabinose acid, and isoquercitrin.

CONCLUSIONS:

Herein, we demonstrate the inhibition of mosquito development by the hydroalcoholic extract of C. brasiliense and suggest substances that may act as active principles.

Amorphous nano morin outperforms native molecule in anticancer activity and oral bioavailability

In the past decade, naturally occurring phytoconstituents have emerged as potential therapeutic agents and alternative to synthetic drugs. However, efficient delivery of hydrophobic phytoconstituents into the body with desired therapeutic efficacy is a key challenge for the pharmaceutical industries due to their insolubility in water and low oral bioavailability. Nanosuspension formulations have shown promises to improve the delivery of the hydrophobic molecules with simultaneously avoiding the drawbacks like carrier toxicity and scale-up issues of other nanotechnology-based drug delivery systems. In this study, we have used morin hydrate (MH), a flavonol, and developed MH nanosuspension formulation (MHNS) to improve its poor physiochemical properties and low oral bioavailability. Different stabilizers with varying concentrations were investigated for preparing nanosuspension. MHNS was characterized by DLS, TEM, FTIR, DSC, powder XRD and was evaluated for its solubility, dissolution, partition coefficient, in-vitro anticancer activity and pharmacokinetics in rats. The optimized nanosuspension formulation, with a size of <100 nm, is capable of increasing aqueous solubility, dissolution rate, and oral bioavailability of MH. Moreover, the therapeutic efficacy, in terms of cytotoxicity to human lung cancer cells, of MH was also increased after formulating into nanosuspension form.

Recent Developments in Nanotechnology for Detection and Control of Aedes aegypti-Borne Diseases

Arboviruses such as yellow fever, dengue, chikungunya and zika are transmitted mainly by the mosquito vector Aedes aegypti. Especially in the tropics, inefficacy of mosquito control causes arboviruses outbreaks every year, affecting the general population with debilitating effects in infected individuals. Several strategies have been tried to control the proliferation of A. aegypti using physical, biological, and chemical control measures. Other methods are currently under research and development, amongst which the use of nanotechnology has attracted a lot of attention of the researchers in relation to the production of more effective repellents and larvicides with less toxicity, and development of rapid sensors for the detection of virus infections. In this review, the utilization of nano-based formulations on control and diagnosis of mosquito-borne diseases were discussed. We also emphasizes the need for future research for broad commercialization of nano-based formulations in world market aiming a positive impact on public health.