Effect of Vetiveria zizanioides L. Root extracts on the malarial vector, Anopheles stephensi Liston

A review of the traditional use of southern African medicinal plants for the treatment of malaria

ETHNOPHARMALOGICAL RELEVANCE

Malaria is one of the most prevalent and deadly parasitic diseases globally, with over 200 million new cases and nearly 500,000 deaths reported annually. It is estimated that approximately half of the world's population lives in malaria endemic areas. Malaria is substantially less prevalent in South Africa than in other African regions and the disease is limited to some regions of the Limpopo, Mpumalanga and KwaZulu-Natal provinces. However, it still has a significant impact on the health of the populations living in those regions. Traditional medicines have long been used in South Africa by multiple ethic groups and many people continue to rely on these natural therapies for their healthcare. The usage of South African medicinal plants in several traditional healing systems to treat malaria have been documented (particularly for Zulu and Venda traditional medicine), although ethnobotanical investigations of other ethnic groups living in endemic malaria areas remains relatively neglected.

AIM OF THE STUDY

To document the use of South African medicinal plants known to be used traditionally to treat Plasmodium spp. infections. We also critically reviewed the literature on the therapeutic properties of these and other South African plants screened against Plasmodium spp. parasites with the aim of highlighting neglected studies and fostering future research in this area.

MATERIALS AND METHODS

Books and ethnobotanical reviews were examined for medicinal plants used specifically for fever. Exclusion criteria were studies not involving southern African medicinal plants. Furthermore, while fever is a common symptom of malaria, if not accompanied by the term "malaria" it was not considered. Databases including PubMed, ScienceDirect, Scopus and Google Scholar were used to source research relevant to southern African plants and malaria. Exclusion criteria were those publications where full articles could not be accessed.

RESULTS

Eighty South African plant species were identified as traditional therapies for malaria. The majority of these species were documented in Zulu ethnobotanical records, despite malaria occurring in only a relatively small portion of the Zulu's traditional territory. Surprisingly, far fewer species were reported to be used by Venda, Ndebele, northern Sotho, Tsonga, Tswana, and Pedi people, despite them living in endemic malaria areas. Interestingly many of the identified species have not been investigated further. This review summarises the available ethnobotanical and laboratory research in this field, with the aim of promoting and focusing research on priority areas.

CONCLUSION

Although malaria remains a serious disease affecting millions of people, medicinal plants while used extensively, have not been given the attention warranted for further investigation.

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.

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.