Larvicidal Compounds Extracted from Helicteres velutina K. Schum (Sterculiaceae) Evaluated against Aedes aegypti L

Exploring the Larvicidal and Adulticidal Activity against Aedes aegypti of Essential Oil from Bocageopsis multiflora

This study investigates the chemical composition of the essential oil obtained from the leaves of Bocageopsis multiflora (Mart.) R.E.Fr (Annonaceae), examining its effectiveness in combating both the larvae and adult forms of Aedes aegypti mosquitoes. Additionally, for a deeper understanding of the insecticidal activity, toxicity properties and molecular docking calculations were conducted using the main compounds of this essential oil. GC/MS analysis revealed the presence of 26 constituents, representing 95.2% of the essential oil, with the major components identified as the sesquiterpenes α-selinene, β-selinene, and β-elemene. Larvicidal assays demonstrated potent activity of this essential oil with significant LC50 values of 40.8 and 39.4 μg/mL at 24 and 48 h, respectively. Adulticidal assessments highlighted strong efficacy with LC50 of 12.5 µg/mL. Molecular docking analysis identified optimal interaction activities of α-selinene and β-selinene with key Aedes proteins. The in silico studies comparing synthetic insecticides with the major sesquiterpenes of the essential oil revealed that β-selinene exhibited a significantly higher binding affinity compared to the other two sesquiterpenes. Also, ADMET studies of the three main sesquiterpenes indicated acceptable drug-like properties. In these findings, safety evaluations showed low toxicity and skin sensitization for the main sesquiterpenes, contrasting with commercial synthetic insecticides. Therefore, in silico analyses suggest promising interactions with Aedes proteins, indicating its potential as an effective alternative to conventional insecticides These results show the larvicidal and adulticidal potential of the essential oil from Bocageopsis multiflora against Aedes aegypti, supported by its predominant constituents, α-selinene, β-selinene and β-elemene.

Nanoemulsions and Solid Microparticles Containing Pentyl Cinnamate to Control Aedes aegypti

The Aedes aegypti mosquito is a vector of severe diseases with high morbidity and mortality rates. The most commonly used industrial larvicides have considerable toxicity for non-target organisms. This study aimed to develop and evaluate liquid and solid carrier systems to use pentyl cinnamate (PC), derived from natural sources, to control Ae. aegypti larvae. The liquid systems consisting of nanoemulsions with different lecithins systems were obtained and evaluated for stability over 30 days. Microparticles (MPs) were obtained by the spray drying of the nanoemulsions using maltodextrin as an adjuvant. Thermal, NMR and FTIR analysis indicated the presence of PC in microparticles. Indeed, the best nanoemulsion system was also the most stable and generated the highest MP yield. The PC larvicidal activity was increased in the PC nanoemulsion system. Therefore, it was possible to develop, characterize and obtain PC carrier systems active against Ae. aegypti larvae.

Phytochemical prospection and larvicidal bioactivity of the janaguba (Himatanthus drasticus) Mart. Plumel (Apocynaceae) latex against Aedes aegypti L. (Diptera: Culicidae)

The aim of this study was to carry out phytochemical prospecting and evaluate the larvicidal activity of Himatanthus drasticus latex extracts against Aedes aegypti. The extracts were obtained by maceration from 5 g of latex powder concentrated separately in 100 mL of methanol, ethyl acetate, and hexane solvents. The concentrations of 100, 200, 300, 400, and 500 ppm of each extract were tested in triplicate with a solution of pyriproxyfen as the positive control and distilled water and dimethylsulfoxide as the negative control. The phytochemical prospection of the methanolic extract showed the presence of phenolic compounds, such as anthocyanins, anthocyanidins, catechins, chalcones, aurones, leucoanthocyanidins, and condensed tannins. The insecticidal bioactivity was most significant for the methanolic extract. The methanolic extract lethal concentrations (LC) of 50 and 90% were 190.76 and 464.74 ppm, respectively. After 48 hours of exposure, the extracts using methanol, ethyl acetate, and hexane at their highest concentrations (500 ppm) caused larval mortality of 100, 73.33, and 66.67%, respectively. These extracts also promoted changes in the external morphology of the larvae, such as damage to the anal papillae, darkening of the body, and reduction in the number of bristles. The methanolic extract showed greater expressivity for morphological changes. The latex of H. drasticus has larvicidal activity against third-stade larvae of A. aegypti and it is more significant when obtained through maceration in methanol. The methanolic extract of H. drasticus latex contains phenolic compounds with insecticidal activity against A. aegypti larvae.

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.

Analysis of the toxicological and pharmacokinetic profile of Kaempferol-3-O-β-D-(6"-E-p-coumaryl) glucopyranoside - Tiliroside: in silico, in vitro and ex vivo assay

Tiliroside is a glycosidic flavonoid present in many plants species including Helicteres velutina K. Schum (Malvaceae sensu lato), commonly known in Brazil as "pitó". This molecule has been shown to have many biological activities, however no study has been carried out to investigate the toxicity of this substance. The present work aimed to evaluate the possible cellular toxicity in silico, in vitro and ex-vivo of the kaempferol-3-O-β-D-(6"-E-p-coumaroyl) glucopyranoside (tiliroside), through chemical structure analysis, toxicity assessment and predictive bioactive properties, using human samples for in vitro and ex-vivo tests. The in silico analysis suggests that tiliroside exhibited great absorption index when penetrating biological membranes. In addition, it also displayed considerable potential for cellular protection against free radicals, and anticarcinogenic, antioxidant, antineoplastic, anti-inflammatory, anti-hemorrhagic and antithrombotic activities. The assessment of the hemolytic and genotoxic effects of tiliroside showed low hemolysis rates in red blood cells and absence of cellular toxicity in the oral mucosa cells. The data obtained indicate that this molecule could be a promising therapeutic approach as a possible new drug with biotechnological potential.

Ovicidal, pupicidal, adulticidal, and repellent activity of Helicteres velutina K. Schum against Aedes aegypti L. (Diptera: Culicidae)

Aedes aegypti is a vector of emerging and neglected diseases, such as dengue, chikungunya, and Zika. Helicteres velutina, known as "pitó" in Brazil, is traditionally used as an insect repellent, and several studies have demonstrated its larvicidal activity. The aim of this study was to investigate this species and evaluate its potential ovicidal, pupicidal, adulticidal, and repellent activity. The viability of the eggs was evaluated using different concentrations of the test substances for 25 days. The hexane fraction killed 72.7% of the eggs, while dichloromethane killed 67.7%. The survival of the pupae and adults was verified after 72 h and 48 h, respectively. The LC₅₀ for the hexane and dichloromethane fractions was 0.12 mg/mL and 8.85 mg/mL for pupae, 8.01 mg/mL and 0.74 mg/mL for adults (tarsal test), and 0.05 mg/mL and 0.23 mg/mL for adults (body test), respectively. Repellency was assessed for 240 min using neonatal Wistar rats on a Y-tube olfactometer. The hexane fraction attracted mosquitoes to the test chamber, while the dichloromethane fraction had a repellent action. The 7,4'-di-O-methyl-8-O-sulfate flavone provides greater repellency, and this finding is similar to the results of the in silico studies that have shown the potential of this substance against adult mosquitoes. This suggests that 7,4'-di-O-methyl-8-O-sulfate flavone may be one of the substances present in the extract from aerial parts of H. velutina that is responsible for the repellent activity mentioned in traditional medicine. These findings provide a better understanding of the insecticidal and repellent activity of the extract, fraction, and compounds isolated from H. velutina against Ae. aegypti, thereby revealing its potential in the development of a more effective botanical insecticide.

Insights on the Larvicidal Mechanism of Action of Fractions and Compounds from Aerial Parts of Helicteres velutina K. Schum against Aedes aegypti L

Viral diseases transmitted by the female Aedes aegypti L. are considered a major public health problem. The aerial parts of Helicteres velutina K. Schum (Sterculiaceae) have demonstrated potential insecticidal and larvicidal activity against this vector. The objective of this research was to investigate the mechanisms of action involved in the larvicidal activity of this species. The cytotoxicity activity of H. velutina fractions and compounds of crude ethanolic extract of the aerial parts of this species was assessed by using fluorescence microscopy and propidium iodide staining. In addition, the production of nitric oxide (NO) and hemocyte recruitment were checked after different periods of exposure. The fluorescence microscopy revealed an increasing in larvae cell necrosis for the dichloromethane fraction, 7,4′-di-O-methyl-8-O-sulphate flavone and hexane fraction (15.4, 11.0, and 7.0%, respectively). The tiliroside did not show necrotic cells, which showed the same result as that seen in the negative control. The NO concentration in hemolymph after 24 h exposure was significantly greater for the dichloromethane fraction and the 7,4′-di-O-methyl-8-O-sulphate flavone (123.8 and 56.2 µM, respectively) when compared to the hexane fraction and tiliroside (10.8 and 8.3 µM, respectively). The presence of plasmocytes only in the dichloromethane fraction and 7,4′-di-O-methyl-8-O-sulphate flavone treatments suggest that these would be the hemocytes responsible for the highest NO production, acting as a defense agent. Our results showed that the larvicidal activity developed by H. velutina compounds is related to its hemocyte necrotizing activity and alteration in NO production.

Sulfated flavanones and dihydroflavonols from willow

Phytochemical profiling of a hybrid species of willow, Salix × alberti L. (S. integra Thunb. × Salix suchowensis W.C. Cheng ex G.Zhu) revealed four sulfated flavonoids, which were then isolated from young stem tissue. The structures of dihydroflavonols (flavanonols) taxifolin-7-sulfate (1) and dihydrokaempferol-7-sulfate (2) and flavanones, eridictyol-7-sulfate (3) and naringenin-7-sulfate (4) were elucidated through NMR spectroscopy and high-resolution mass spectrometry. The identified sulfated flavanones and dihydroflavonols have not been previously seen in plants, but the former have been partially characterised as metabolites in mammalian metabolism of dietary flavonoids. In addition to providing full spectroscopic characterisation of these metabolites for the first time, we also compared the in vitro antioxidant properties, via the DPPH radical scavenging assay, of the parent and sulfated flavanones, which showed that 7-sulfation of taxifolin and eriodictyol attenuates but does not remove anti-oxidant activity.

Sulphated flavones and pregnane-type steroids from Helicteres viscida

In our search for anti-inflammatory constituents from Vietnamese plants, the methanolic extract of Helicteres viscida was found to exhibit inhibitory effect on LPS-induced NO production in RAW264.7 cells. Phytochemical investigation of this plant led to isolation of four sulphated flavones (1-4), including one new compound 5,3',4'-trihydroxy-7-methoxy-8-O-sulphate flavone (1), and two pregnane-type steroids (5 and 6), including one new compound 7-epi-heligenin B (5). Their structures were elucidated by 1D and 2D NMR as well as HR-QTOF-MS experiments. Among isolated compounds, heligenin B (6) exhibited potent inhibitory effect on LPS-induced NO production in RAW264.7 cells with IC₅₀ of 1.23 ± 0.05 µM. The activity of 6 was comparable to that of the positive control cardamonin.