Efficacy of essential oils of aromatic plants as larvicide for the management of filarial vector Culex quinquefasciatus Say (Diptera: Culicidae) with special reference to Foeniculum vulgare

The potential of Apiaceae species as sources of singular phytochemicals and plant-based pesticides

The Apiaceae Lindl. (=Umbelliferae Juss.), which includes several economical important vegetables, herbs, and spices, is one of the most numerous plant family. Umbelliferous crops (namely anise, fennel, carrot, coriander, parsley, etc.) are also valuable sources of botanical flavoring agents and fragrances. In addition, Apiaceae species yield a wide variety of distinctive specialized metabolites (i.e, volatile phenylpropanoids, furanocoumarins, sesquiterpene coumarins, polyacetylenes, and phthalides), some of them been described as uncommon natural phytochemicals exclusive of the family, which offers a great potential for bioprospection. Numerous studies have pointed out the outstanding biological activity of extracts and several classes of phytochemicals from Apiaceae species. Emphasis has been given to essential oils (EOs) and their constituents activities, most likely because this type of plant added value product benefits from a larger acceptance and application potential in integrated pest management (IPM) and integrated vector management (IVM) programs. Several species of the family offer a variety of unique compounds with great potential as biopesticidal and/or synergizing agents. Investigations covering their activity toward agricultural pests and phytopathogens have increased in the last years, nevertheless the interest remains strongly focus on arthropod species, predominantly those acting as vectors of human diseases. From our survey, it is patent the gap of knowledge concerning the potential molluscicidal properties of Apiaceae extracts/phytochemicals, as well as their herbicidal activities against invasive plant species. In this review, we propose to highlight the potential of Apiaceae species as suitable sources of bioactive phytochemicals with great relevance within the frame of plant-based pesticides R&D, and will discuss their applicability in real-world scenarios considering the recent developments regarding the design of stable formulations incorporating Apiaceae bioactive products. We expect that this review will encourage researchers to consider undervalued Apiaceae species as alternative sources of bioactive compounds and will give a contribute to the field by suggesting new research topics.

Larvicidal Activity against Aedes Aegypti of Foeniculum Vulgare Essential Oils from Portugal and Cape Verde

Dengue is a potentially fatal mosquito-borne infection with 50 million cases per year and 2.5 billion people vulnerable to the disease. This major public health problem has recurrent epidemics in Latin America and occurred recently in Cape Verde and Madeira Island. The lack of anti-viral treatment or vaccine makes the control of mosquito vectors a high option to prevent virus transmission. Essential oil (EO) constituents can affect insect's behaviour, being potentially effective in pest control. The present study evaluated the potential use of Foeniculum vulgare (fennel) EO in the control of the dengue vector Aedes aegypti. EOs isolated from fennel aerial parts collected in Cape Verde and from a commercial fennel EO of Portugal were analysed by NMR, GC and GC-MS. trans-Anethole (32 and 30%, respectively), limonene (28 and 18%, respectively) and fenchone (10% in both cases) were the main compounds identified in the EOs isolated from fennel from Cape Verde and Portugal, respectively. The larvicidal activity of the EOs and its major constituents were evaluated, using WHO procedures, against third instar larvae of Ae. aegypti for 24 h. Pure compounds, such as limonene isomers, were also assayed. The lethal concentrations LC50, LC90 and LC99 were determined by probit analysis using mortality rates of bioassays. A 99% mortality of Ae. aegypti larvae was estimated at 37.1 and 52.4 μL L−1 of fennel EOs from Cape Verde and Portugal, respectively. Bioassays showed that fennel EOs from both countries displayed strong larvicidal effect against Ae. aegypti, the Cape Verde EO being as active as one of its major constituents, (-)-limonene.

Larvicidal, ovicidal and pupicidal activities of Gliricidia sepium (Jacq.) (Leguminosae) against the malarial vector, Anopheles stephensi Liston (Culicidae: Diptera)

OBJECTIVE

To investigate the potentiality of mosquitocidal activity of Gliricidia sepium (G. sepium) (Jacq.) (Leguminosae).

METHODS

Twenty five early third instar larvae of Anopheles stephensi (An. stephensi) were exposed to various concentrations (50-250 ppm) and the 24 h LC(50) values of the G. sepium extract was determined by probit analysis. The ovicidal activity was determined against An. stephensi to various concentrations ranging from 25-100 ppm under laboratory conditions. The eggs hatchability was assessed 48 h post treatment. The pupicidal activity was determined against An. stephensi to various concentrations ranging from 25-100 ppm. Mortality of each pupa was recorded after 24 h of exposure to the extract.

RESULTS

Results pertaining to the experiment clearly revealed that ethanol extract showed significant larvicidal, ovicidal and pupicidal activity against the An. stephensi. Larvicidal activity of ethanol extracts of G. sepium showed maximum mortality in 250 ppm concentration (96.0±2.4)%. Furthermore, the LC(50) was found to be 121.79 and the LC(90) value was recorded to be 231.98 ppm. Ovicidal activity of ethanol extract was assessed by assessing the egg hatchability. Highest concentration of both solvent extracts exhibited 100% ovicidal activity. Similarly, pupae exposed to different concentrations of ethanol extract were found dead with 58.10% adult emergence when it was treated with 25 ppm concentration. Similarly, 18.36 (n=30; 61.20%); 21.28(70.93) and 27.33(91.10) pupal mortality was recorded from the experimental pupae treated with 50, 75 and 100 ppm concentration of extracts. Three fractions have been tested for their larvicidal activity of which the Fraction 3 showed the LC(50) and LC(90) values of 23.23 and 40.39 ppm. With regard to the ovicidal effect fraction 3 showed highest ovicidal activities than the other two fractions. Furthermore, there were no hatchability was recorded above 50 ppm (100% egg mortality) in the experimental group. Statistically significant pupicidal activity was recorded from 75 ppm concentration.

CONCLUSIONS

From the results it can be concluded the crude extract of G. sepium is an excellent potential for controlling An. stephensi mosquito. It is apparent that, fraction 3 possess a novel and active principle which could be responsible for those biological activities.

Effects of Mirazid(®) and myrrh volatile oil on adult Fasciola gigantica under laboratory conditions

OBJECTIVE

To evaluate the effects of Mirazid(®) and myrrh volatile oil on adult Fasciola gigantica (F. gigantica ) under laboratory conditions.

METHODS

The effects of oleoresin extract of myrrh (Mirazid(®)) and myrrh volatile oil on the surface morphology of adult F. gigantica following treatment in vitro had been determined by scanning electron microscopy. The results were compared with those observed in the fluke tegument following incubation in triclabendazole sulphoxide (TCBZ-SO), active form, (Fasinex(®), Ciba-Geigy).

RESULTS

Observations of the efficacy of Mirazid(®) oleoresin extract and myrrh volatile oil indicated that both products showed dose-dependent anthelmintic efficacy. The anterior half of the fluke was consistently more severely affected than the posterior half. The surface changes induced by Mirazid(®) oleoresin extract were less severe than those observed after exposure to either myrrh volatile oil or TCBZ-SO. Flukes showed swelling after these treatments, but its level and blebbing were much greater with myrrh volatile oil; in which patches of tegumental sloughing were observed in the apical cone and the posterior mid-body region of flukes. This was not observed after treatment with Mirazid(®) oleoresin extract.

CONCLUSIONS

The comparatively more disruption, observed in myrrh volatile oil exposed specimens, compared to that exposed to Mirazid(®) oleoresin extract might suggest that the anthelmintic activity of Mirazid(®) oleo resin extract was attributed to its content of volatile oil. So, increasing the concentration of myrrh volatile oil in Mirazid(®) might possibly help to developing its anthelmintic activity.

Evaluation of aqueous and ethanol extract of bioactive medicinal plant, Cassia didymobotrya (Fresenius) Irwin & Barneby against immature stages of filarial vector, Culex quinquefasciatus Say (Diptera: Culicidae)

OBJECTIVE

To evaluate aqueous and ethanol extract of Cassia didymobotrya leaves against immature stages of Culex quinquefasciatus.

METHODS

The mortality rate of immature mosquitoes was tested in wide and narrow range concentration of the plant extract based on WHO standard protocol. The wide range concentration tested in the present study was 10 000, 1 000, 100, 10 and 1 mg/L and narrow range concentration was 50, 100, 150, 200 and 250 mg/L.

RESULTS

2nd instar larvae exposed to 100 mg/L and above concentration of ethanol extract showed 100% mortality. Remaining stages such as 3rd, 4th and pupa, 100% mortality was observed at 1 000 mg/L and above concentration after 24 h exposure period. In aqueous extract all the stages 100% mortality was recorded at 1 000 mg/L and above concentration. In narrow range concentration 2nd instar larvae 100% mortality was observed at 150 mg/L and above concentration of ethanol extract. The remaining stages 100% mortality was recorded at 250 mg/L. In aqueous extract all the tested immature stages 100% mortality was observed at 250 mg/L concentration after 24 h exposure period. The results clearly indicate that the rate of mortality was based dose of the plant extract and stage of the mosquitoes.

CONCLUSIONS

From this study it is confirmed and concluded that Cassia didymobotrya is having active principle which is responsible for controlling Culex quinquefasciatus. The isolation of bioactive molecules and development of simple formulation technique is important for large scale implementation.

Lethal effect of Streptomyces citreofluorescens against larvae of malaria, filaria and dengue vectors

OBJECTIVE

To investigate lethal effect of culture filtrates of Streptomyces citreofluorescens (S. citreofluorescens) against Anopheles stephensi (An. stephensi), Culex quinquefasciatus (Cx. quinquefasciatus), and Aedes aegypti (Ae. aegypti) larvae vectors for malaria, filarial and dengue.

METHODS

The culture filtrates obtained from S. citreofluorescens 2528 was grown in Potato Dextrose Broth (PDB), filtrated and used for the bioassay after a growth of 15 days.

RESULTS

The results demonstrated that the An. stephensi shows mortalities with LC(50), LC(90) values of first instar 46.8 μL/mL, 79.5 μL/mL, second instar 79.0 μL/mL, 95.6 μL/mL, third instar 79.0 μL/mL, 136.9 μL/mL, and fourth instar 122.6 μL/mL, 174.5 μL/mL. Whereas, The Cx. quinquefasciatus were found effective on first instar 40.0 μL/mL, 138.03 μL/mL, second instar 80.0 μL/mL, 181.97 μL/mL, third instar 100.0 μL/mL, 309.2 μL/mL, and fourth instar 60.0 μL/mL, 169.82 μL/mL. The Ae. aegypti were successfully achieved susceptible with higher concentrations in comparisons of An. stephensi and Cx. quinquefasciatus larvae. These outcomes of the investigations have compared with the Chitinase of Streptomyces griseus (S. griseus) C6137 that shows 90%-95% mortality.

CONCLUSIONS

These new findings significantly permitted that the culture filtrates of S. citreofluorescens can be used as bacterial larvicides. This is an environmentally safe approach to control the vectors of malaria, dengue and filariasis of tropical areas.