Larvicidal Potential of the Halogenated Sesquiterpene (+)-Obtusol, Isolated from the Alga Laurencia dendroidea J. Agardh (Ceramiales: Rhodomelaceae), against the Dengue Vector Mosquito Aedes aegypti (Linnaeus) (Diptera: Culicidae)

Abstract

Dengue is considered a serious public health problem in many tropical regions of the world including Brazil. At the moment, there is no viable alternative to reduce dengue infections other than controlling the insect vector, Aedes aegypti Linnaeus. In the continuing search for new sources of chemicals targeted at vector control, natural products are a promising alternative to synthetic pesticides. In our work, we investigated the toxicity of a bioactive compound extracted from the red alga Laurencia dendroidea J. Agardh. The initial results demonstrated that crude extracts, at a concentration of 5 ppm, caused pronounced mortality of second instar A. aegypti larvae. Two molecules, identified as (−)-elatol and (+)-obtusol were subsequently isolated from crude extract and further evaluated. Assays with (−)-elatol showed moderate larvicidal activity, whereas (+)-obtusol presented higher toxic activity than (−)-elatol, with a LC50 value of 3.5 ppm. Histological analysis of the larvae exposed to (+)-obtusol revealed damage to the intestinal epithelium. Moreover, (+)-obtusol-treated larvae incubated with 2 µM CM-H2DCFDA showed the presence of reactive oxygen species, leading us to suggest that epithelial damage might be related to redox imbalance. These results demonstrate the potential of (+)-obtusol as a larvicide for use against A. aegypti and the possible mode of action of this compound.

Phytochemical Investigation of Three Cystoseira Species and Their Larvicidal Activity Supported with In Silico Studies

“…Seaweeds, with their great chemical diversity, are utilized as a foodstuff for human and animal food, fertilizers, cosmetics, and medicinal products [ 18 , 19 ]. Seaweed extracts have proven competence for controlling and repelling various insect pests such as cereal aphids, Schizaphis graminum [ 20 ], the cotton stainer bug, Dysdercus cingulatus [ 21 ], mosquitoes [ 22 , 23 ], the tomato moth, Tuta absoluta [ 24 ], the termite, Microtermes obesi [ 25 ], maize weevil, Sitophilus zeamais [ 26 ] and the Asian citrus psyllid, Diaphorina citri [ 27 ]. Some studies documented the insecticidal effects of seaweeds of Egyptian origin as Caulerpa prolifera , Caulerpa serrulata , Jania rubens , Nitophyllum punctatum Padina pavonica , Chara vulgaris, Parachlorella kessleri , Ulva intestinalis and Cladophora glomerata [ 28 , 29 ].…”

Screening and evaluation of different algal extracts and prospects for controlling the disease vector mosquito Culex pipiens L.

“…Also, the red algae are rich with polyphenolic and terpenes compounds compared to green and brown algae these triterpenes inhibit the protein responsible for the cholesterol transportation during the larval development resulting in larval mortality ( Blunt et al, 2011 , Bibi et al, 2020 ). In addition, halogenated sesquiterpene (−)-elatol and (+)-obtusol, brominated-oxygenated heterocyclic and halogenated, polyhalogenated compounds obtained from red algae exhibited larvicidal activity against mosquitoes ( Abou-Elnaga et al, 2011 , Salvador-Neto et al, 2016 ). Deepak et al, (2019) reported that the presence of alkyl halides, carboxylic acid, alkynes, and amides in the methanolic extract of red algae are responsible for its larvicidal effect.…”

Seaweed for climate mitigation, wastewater treatment, bioenergy, bioplastic, biochar, food, pharmaceuticals, and cosmetics: a review

“…The authors added that Cladophora glomerata -derived fatty acids, including myristic, palmitoleic, lauric, and capric acids, were found to have 3–14 ppm lethal concentration 50 against Aedes triseriatus . Similarly, Salvador-Neto et al ( 2016 ) reported that Laurencia dendroidea derived elatol and halogenated sesquiterpene, (+)-obtusol caused larvicidal mortality of 30% and 9%, respectively, at 10 parts per million concentrations against A. aegypti within 24 h. Additionally, obtusol extracts have shown concentration-dependent larvicidal activities. To this end, seaweed extract has promising antiviral and mosquitocidal activities, and more research is needed against more agents with different integrations and applied protocols.…”