Larvicidal activity of Allium fistulosum (spring onion) leaf extract, Ocimum x citriodorum (lemon basil) leaf extract, and Cymbopogan citratus (lemongrass) leaf extract against Aedes aegypti: A comparative study
Proponents: Marjorie P. Oclarit
Jan Roliesa P. Llamos
Jakilyn R. Mulla
Coincide to World Health Organization (WHO), mosquitos are pests that affect the health of many human beings and may bring different kinds of diseases that includes: mosquito-borne disease, dengue fever, chikungunya virus infection, and etc. Dengue was first recognized in the Philippines and Thailand in the year 1950. Now, Asian and Latin American countries are at risk. Aedes aegypti is now spreading all over the world. According to the World Health Organization (WHO), Aedes aegypti causes millions of deaths every year. In the past 30 years, these cases of A. aegypti had increased 30 times as great and other countries have been reporting increased of diseases that are caused by these mosquitoes. About half of the world’s population is now at risk. Recent estimate states that 390 million are affected by dengue infections per year. Another certain study indicates 128 countries with 3.9 billion people are affected. According to DOH statistical report (2018) in the cases of victims of dengue in the Philippines, a number of 20,108 were affected. Monthly report states that in Region XI there are 586 number of cases within 2 months. All cases of diseases caused by A. aegypti are typically ongoing that motivates the researchers to conduct a study.
Using chemical insecticides can bring threats to the health of the humans, habitats of the animals and biological balance in the environment. Having an alternative and natural larvicide is the most effective way to lessen the threats that the chemicals from a commercially used larvicide can bring. As of now, humankind uses insecticides that has great negative effects such as harming animals, plants, and all living beings for it contains harmful chemicals and mosquitoes’ throughout the years build resistance to insecticide.
Related studies showed that plants that contain alkaloids can be a potential larvicidal agent against mosquitos. Most of these alkaloids can be found in some plants that are used as spices, this includes Allium fistulosum (spring onion), Ocimum x citriodorum (lemon basil), and Cymbopogan citratus (lemongrass).
MATERIAL AND METHODS
Phase I – Plant Preparation for Extraction
Collection of Plants
The plants were collected at the Public Market in Poblacion, Nabunturan. The plants weighed 5 kg each.
Extraction of Crude Extract from the Plant Samples
The plants undergone air dry process for 48 hours and were homogenized using a blender. Then the plants were soaked with ethanol for 48 hours with a ratio of 1:2 where 1 part plant and 2 parts ethanol. After 48 hours, it was filtered using a filter paper no. 1. Beakers were used for the collection of filtrate. Modified evaporation using oil bath technique was used for the modified rotary evaporation. The plant filtrate containing 250 mL was poured in the 300 mL distilling flask. It was then put in the water trough, which contained cooking oil, and submerged the bottom of the distilling flask 1.5 inches while ensuring the oil to not overflow. Then, the hot plate was turned on to 300° C. After it, the condensed ethanol was collected in the beaker while the extract that remained at the bottom of the flask was also collected separately.
Phase II – Mosquito Larvae Experimentation
Culture of Mosquito Larvae
The larvae was cultured and was put in a bucket of water and checked frequently until it develop into 3rd – 4th instar level. The larvae was identified in the Nabunturan Health Center.
The concentrations of extracts are as follows: seventy-five percent (75%), and one-hundred percent (100%). The experiment consists of 2 treatments with 5 replicates each for the plant samples, positive control (Baygon), negative control (distilled water), and the Ethanol. The extracts were placed in the petri dishes with three larvae each. The time (minutes) when the larvae showed mortality results will be recorded.
Disposal of Mosquito Larvae
After the experiment, the larvae were mixed in the water and was boiled for the disposal (Buckner, 1934). And was poured in an area with direct sunlight.
Phase III – Data Collection Analysis
One-way Anova was used to determine the significant difference of the effectiveness of plant extracts of Allium fistulosum (spring onion), Ocimum x citriodorum (lemon basil), and Cymbopogan citratus (lemongrass) on mosquito larvae and was tested at 0.01 level of significance.
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