Phytochemical study of Waltheria viscosissima and evaluation of its larvicidal activity against Aedes aegypti

Phytochemical prospection, hemagglutinating and insecticidal activity of saline extracts from the seeds of Tamboril (Enterolobium contortisiliquum) Vell. Morong (Fabaceae) on Aedes aegypti (Diptera: Culicidae)

This study evaluated the insecticidal activity of crude extracts from Enterolobium contortisiliquum (Vell.) seeds on eggs and larvae of A. aegypti, and also verified the phytochemical profile and the presence of lectins in the extract. The 0.15 M NaCl saline solution was used as the extracting substance. For tests with eggs and larvae, the crude extract was used in its raw form (RCE) and boiled at 100º C for 5 min (BCE). Concentrations of 4.68; 9.37; 18.75; 28.13; 37.13 and 46.89 mg/mL, with distilled water as a negative control. Assays were performed in triplicate. The results were subjected to analysis of variance, Tukey's test and Log-Probit analysis to determine LC50 and LC90. BCE showed better results on eggs than RCE, managing to prevent the hatching of larvae in 81.66% ± 10.40 of treated eggs, at a concentration of 46.89 mg/mL. The LC50 and LC90 were set at 35.95 and 52.67 mg/mL, respectively. In tests with larvae, concentrations of 46.89 and 37.13 mg/mL, for RCE and BCE, caused 100% mortality in 24 hours of exposure. Larval mortality at the other concentrations increased with exposure time extending to 48 h. RCE, at 48 h exposure is the most promising extract on larvae (E = 72.77%, LC90 = 10.86 mg/mL). In RCE, the presence of lectins and secondary metabolites: flavonoids, xanthones and phenols, were detected. The results demonstrate the potential of E. contortisiliquum seed extracts with ovicidal and larvicidal action on A. aegypti.

Old Meets New: Mass Spectrometry-Based Untargeted Metabolomics Reveals Unusual Larvicidal Nitropropanoyl Glycosides from the Leaves of Heteropterys umbellata

The Aedes aegypti (Diptera: Culicidae) mosquito is the vector of several arboviruses in tropical and subtropical areas of the globe, and synthetic pesticides remain the most widely used combat strategy. This study describes the investigation of secondary metabolites with larvicidal activity from the Malpighiaceae taxon using a metabolomic and bioactivity-based approach. The workflow initially consisted of a larvicidal screening of 394 extracts from the leaves of 197 Malpighiaceae samples, which were extracted using solvents of different polarity, leading to the selection of Heteropterys umbellata for the identification of active compounds. By employing untargeted mass spectrometry-based metabolomics and multivariate analyses (PCA and PLS-DA), it was possible to determine that the metabolic profiles of different plant organs and collection sites differed significantly. A bioguided approach led to the isolation of isochlorogenic acid A (1) and the nitropropanoyl glucosides karakin (2) and 1,2,3,6-tetrakis-O-[3-nitropropanoyl]-beta-glucopyranose (3). These nitro compounds exhibited larvicidal activity, possibly potentialized by synergistic effects of their isomers in chromatographic fractions. Additionally, targeted quantification of the isolated compounds in different extracts corroborated the untargeted results from the statistical analyses. These results support a metabolomic-guided approach in combination with classical phytochemical techniques to search for natural larvicidal compounds for arboviral vector control.

The bioprospecting potential of Clusia fluminensis Planch. & Triana: a scoping review

Many biological activities are described for the Clusiaceae family. Clusia fluminensis, a species from Brazilian flora, is mainly employed for ornamental purposes. This review aimed to depict the current knowledge of C. fluminensis from a bioprospecting standpoint. "Clusia fluminensis" search term was applied in Scopus, Web of Science, PubMed and Bireme databases according to PRISMA-ScR statement. Selected papers on Phytochemistry or Bioactivity followed hand searching procedures. Bioactivity preclinical studies considered in vitro or in vivo biological systems, treated with plant extracts or isolated compounds. The outcomes were compared with standard or no treatment control groups. Critical appraisal of individual trials considered completeness in the research fields. Our results showed that 81% of the selected papers presented high level of completeness, 69% revealed phytochemical parameters and 31% biological applications of plant extracts and isolated compounds. Polyisoprenylated benzophenones, terpenoids, sterols and phenolic compounds were identified. Antiviral, insecticidal and snake antivenom activities were reported. In conclusion, the phytochemical data reinforce the reported activities. Potential applications in personal care, nutritional supplementation and pharmaceutical, food, chemical or textile industries were also identified. Toxicological and phytochemical complementary studies may be required.

Role of Phenylpropanoids and Flavonoids in Plant Resistance to Pests and Diseases

Phenylpropanoids and flavonoids are specialized metabolites frequently reported as involved in plant defense to biotic or abiotic stresses. Their biosynthetic accumulation may be constitutive and/or induced in response to external stimuli. They may participate in plant signaling driving plant defense responses, act as a physical or chemical barrier to prevent invasion, or as a direct toxic weapon against microbial or insect targets. Their protective action is described as the combinatory effect of their localization during the host's interaction with aggressors, their sustained availability, and the predominance of specific compounds or synergy with others. Their biosynthesis and regulation are partly deciphered; however, a lot of gaps in knowledge remain to be filled. Their mode of action on microorganisms and insects probably arises from an interference with important cellular machineries and structures, yet this is not fully understood for all type of pests and pathogens. We present here an overview of advances in the state of the art for both phenylpropanoids and flavonoids with the objective of paving the way for plant breeders looking for natural sources of resistance to improve plant varieties. Examples are provided for all types of microorganisms and insects that are targeted in crop protection. For this purpose, fields of phytopathology, phytochemistry, and human health were explored.

Mosquito Larvicides of Partial and Combinations Extract of Ethnobotanical Plant from North Sulawesi, Indonesia

<b>Background and Objective:</b> Diseases caused by microbes vectored by mosquitoes are still a health problem in tropical countries today. DHF and Malaria are the two primary diseases vectored by mosquitoes, the morbidity and mortality rates have increased in low countries until now. However, the best way to control these two diseases is to control vectors, namely mosquitoes. Research has been conducted to determine the bioactive content and larvicidal activity of local plant extracts of North Sulawesi. <b>Materials and Methods:</b> The clove and trumpet flower samples were obtained from Minahasa, while the nutmeg samples were obtained from Sitaro Regency. Empirically, people use plant parts to repel mosquitoes. Extraction of plant simplicia was carried out by the maceration method. Qualitative and quantitative methods carried out the phytochemical content analysis. Qualitative analysis uses Harborne's (1996) method while qualitative analysis uses the UV Vis Spectrophotometer method. Toxicity tests were carried out on mosquito larvae developed in the laboratory. <b>Results:</b> The results showed that combining clove leaf extract, nutmeg flesh extract and trumpet flower synergistically increased the bioactive content. Flavonoids increased in the combination of extracts compared to partial extracts. The combination of extracts showed the highest toxicity to mosquito larvae (LC<sub>50</sub>: 22.541 mg L<sup>1</sup>), while the lowest was the partial extract of clove leaves with LC<sub>50</sub> (54.965 mg L<sup>1</sup>). <b>Conclusion:</b> The combination of extracts showed the best toxicity activity on mosquito larvae. Research on bioactive characteristics and toxicity in adult mosquitoes needs to be carried out in the future.

Antinociceptive, anti-inflammatory and antioxidant activities of the crude ethanolic extract and alkaloid fraction of Waltheria viscosissima A. St. - Hil. (Malvaceae)

ETHNOPHARMACOLOGICAL RELEVANCE

The Waltheria viscosissima A. St.- Hil (Malvaceae) is also known as 'Malva branca', has been reported as ethnopharmacologically useful plant containing antinociceptive and anti-inflammatory properties, but scientific evidence is absent.

AIM OF THE STUDY

Elucidate the antinociceptive, anti-inflammatory and antioxidant activity of the crude ethanol extract (EEBWa.v) and alkaloid fraction (FAWa.v) of aerial parts of the W. viscosissima in healthy mice with induced inflammation.

MATERIALS AND METHODS

EEBWa.v and FAWa.v (50, 100 and 200 mg/kg) and morphine (10 mg/kg) were used in vivo tests of chemical nociception induced by acetic acid (0.6%; 10 mg/kg) and formalin (2.5%) in Swiss male mice. Acute inflammation was induced by carrageenan (1%) in vivo tests and there were several groups tested. The control (inflammation induced without treatment) and the groups treated with EEBWa.v (100 mg/kg), FAWa.v (100 mg/kg) and dexamethasone (2 mg/kg). After this procedure, the animals were euthanized and the peritoneal fluid was collected to evaluate cell migration and redox balance (malondialdehyde - MDA and Total Antioxidant Capacity - TAC).

RESULTS

The morphine, EEBWa.v (50 and 100 mg/kg) and FAWa.v (100 mg/kg) significantly reduced the number of abdominal writhes compared to the control group. FAWa.v (100 mg/kg) was superior to FAWa.v (200 mg/kg). In the formalin-induced nociception model (neurogenic phase) EEBWa.v (50 and 200 mg/kg) significantly reduced the number of paw licks. In the inflammatory phase with peripheral action, FAWa.v (100 mg/kg) was superior to EEBWa.v (200 mg/kg). EEBWa.v and FAWa.v (100 mg/kg) proved to be significant for the next experiments. Both samples showed reduction in cell migration, as well as those treated with dexamethasone, in animals with inflammation induced by carrageenan, compared to the untreated group. The redox balance (TAC and MDA) revealed that only EEBWa.v (100 mg/kg) had higher antioxidant potential than the untreated group and the dexamethasone group, p < 0.005 and p < 0.001, respectively. FAWa.v (100 mg/kg) did not show antioxidant activity superior to EEBWa.v. It was also detected that EEBWa.v and FAWa.v (100 mg/kg) failed to inhibit lipid peroxidation.

CONCLUSIONS

The W. viscosissima stimulates pain control, which can be mediated by both central and peripheral action. These bioactive compounds showed promising and potential to replace standard medicines. This bioactive effect is statistically similar to morphine and dexamethasone, standard medicines on the market, but with the advantage of antioxidant activity.

Sidastrum paniculatum (L.) Fryxell (Malvaceae): A Promising Source of Bioactive Sulfated Flavonoids Against Aedes aegypti L

Aedes aegypti L. is known as the most relevant vector mosquito for viruses such as yellow fever, chikungunya, dengue, and Zika, especially in places with unplanned urbanization, and erratic water supply. Plants used in folk medicine have become a useful source of active compounds with the potential to control the dissemination of Ae. aegypti. Compounds isolated from Malvaceae sensu lato have been previously reported as larvicides, repellents, and insecticides. Recent studies have demonstrated the anti Ae. aegypti activity of sulfated flavonoids, an uncommon type of flavonoid derivatives. This research reports the phytochemical investigation of Sidastrum paniculatum (L.) Fryxell, a Malvaceae species with the potential against Ae. aegypti. Chromatographic procedures resulted in the isolation of the compounds: stearic acid (1), N-trans-feruloyltyramine (2), acacetin (3), apigenin (4), tiliroside (5), along with the sulfated flavonoids: wissadulin (6), 7,4'-di-O-methyl-8-O-sulfate flavone (7), yannin (8), beltraonin (9a), 7-O-sulfate isoscutellarein (paniculatumin) (9b), and condadin (10). This is the first report of compound 7-O-sulfate isoscutellarein (9b). The structures were elucidated by spectroscopic analysis (NMR, LC-HRMS and FT-IR). The sulfated flavonoids identified were submitted to a ligand-based and structure-based virtual screening against two targets: 1YIY (from adult Ae. aegypti) and 1PZ4 (from Ae. aegypti larvae). The results indicated that when the O-sulfate group is bearing the position 7, the structures are potentially active in 1PZ4 protein. On the other hand, flavonoids with the O-sulfate group bearing position 8 were showed to be more likely to bind to the 1YIY protein. Our findings indicated that S. paniculatum is a promising source of sulfated flavonoids with potential against Ae. aegypti.

Plant-derived alkaloids acting on dengue virus and their vectors: from chemistry to pharmacology

Dengue is a mosquito-borne viral infection, with its prevention and control depending on effective vector control measures. At present, dengue virus (DENV) is an epidemic in more than 100 countries of Southeast Asia, Africa, Eastern Mediterranean, the Americas and the Western Pacific. Several alkaloids isolated from natural herbs can serve as a reservoir for antiDENV drug development. Traditionally, plant extracts rich in alkaloids are used for the treatment of fever and have also revealed antimicrobial activity against various pathogenic bacteria, fungi and virus. The present narrative review collates the literature-based scenario of alkaloids and derivatives acting on DENV. The mechanism of action of such alkaloids with antiDENV and vector activity is also discussed.

The Potential of Biologically Active Brazilian Plant Species as a Strategy to Search for Molecular Models for Mosquito Control

Natural products are a valuable source of biologically active compounds and continue to play an important role in modern drug discovery due to their great structural diversity and unique biological properties. Brazilian biodiversity is one of the most extensive in the world and could be an effective source of new chemical entities for drug discovery. Mosquitoes are vectors for the transmission of dengue, Zika, chikungunya, yellow fever, and many other diseases of public health importance. These diseases have a major impact on tropical and subtropical countries, and their incidence has increased dramatically in recent decades, reaching billions of people at risk worldwide. The prevention of these diseases is mainly through vector control, which is becoming more difficult because of the emergence of resistant mosquito populations to the chemical insecticides. Strategies to provide efficient and safe vector control are needed, and secondary metabolites from plant species from the Brazilian biodiversity, especially Cerrado, that are biologically active for mosquito control are herein highlighted. Also, this is a literature revision of targets as insights to promote advances in the task of developing active compounds for vector control. In view of the expansion and occurrence of arboviruses diseases worldwide, scientific reviews on bioactive natural products are important to provide molecular models for vector control and contribute with effective measures to reduce their incidence.

Efficacy of Antimicrobial and Larvicidal Activities of Green Synthesized Silver Nanoparticles Using Leaf Extract of Plumbago auriculata Lam

This work reports the synthesis of silver nanoparticles (AgNPs) using aqueous extract of Plumbago auriculata, and evaluates their antibacterial and larvicidal activities. The synthesized silver nanoparticles were characterized by various spectroscopy techniques, such as FTIR, XRD, TEM, EDX, Zeta potential, and DLS. The synthesized AgNPs exhibited significant antibacterial activity against Gram-positive and Gram-negative bacteria, such as Bacillus subtilis, Staphylococcus aureus, Escherichia coli, and Klebsiella pneumoniae. Furthermore, synthesized nanoparticles inhibited the fourth instars larvae of Aedes aegypti and Culex quinquefasciatus at the concentration of 45.1 and 41.1 µg/mL respectively. Results of dose-dependent studies showed that synthesized nanoparticles were also effective at low concentrations. Molecular docking studies performed with the salivary protein and odorant-binding protein of Aedes aegypti and Culex quinquefasciatus demonstrated that the naphthoquinone compound plumbagin exhibited reliable binding affinity towards the two enzymes. The findings thus reveal that the plant extract and its nanoparticles can be a better alternative to available chemicals to control mosquitos.