Larvicidal Activity of Rain Tree (Albizia saman) Methanolic Leaves Extracts against Aedes aegypti Larvae

Abstract

INTRODUCTION

Dengue and Zika virus have been causing a huge problem all throughout the world, especially in the Philippines. These issues became more difficult to remove due to the widespread distribution and rapid reproduction of Aedes aegypti mosquitoes. The use of chemical agents on the other hand, affect humans and environmental health. Thus, there is a need for a new search of effective yet safe and organic treatment. inthis study, Albizia saman methanolic leaf extract was evaluated to determine the bioactive compounds present and to analyze its larvicidal activity against Aedes aegypti.

METHODS

Albizia saman leaves were collected, authenticated in University of the Philippines Museum of Natural History and were then prepared for methanolic extraction. The Albizia saman methanolic leaf extract was screened for presence of bioactive compounds that have larvicidal activities. Fourth instar larvae of Aedes aegypti were gathered from Institute of Weed Science, Entomology and Plant Pathology and were cultured in petri plates with different concentrations of the methanolic leaf extracts (25%,50%,75%), normal saline solution (negative control) and black pepper solution (positive control). The larvae were monitored for 24 hours for any changes in the behavior, morphology and mortality rate of the mosquitoes.

RESULTS

Bioactive compounds that have larvicidal activities against Aedes aegypti were found to be present in Albizia saman methanolic leaves extract such as alkaloids (++), flavonoids (+), and saponins (+). Thirty minutes after application of the extracts, the mortality of the larvae increased. The 75% concentration exhibited the highest mean mortality of 8.67. Meanwhile, the 25% and 50% exhibited mean mortalities of 4.00 and 4.67, respectively. As to the morphology and behavior of the Aedes aegypti, these were observed: (1) agitated behavior; (2) narrowing of abdomen; (3) darkening of abdominal canal and; (4) anal gill deterioration. High mortality and many kinds of morphological and behavioral abnormalities were mainly observed.

DISCUSSIONS

Results showed that Albizia saman methanolic leaf extract drastically affected the mortality, morphology and behavior of Aedes aegypti. In conclusion, it could be used as an organic larvicide. However, relevant studies with the use of different solvents and plant parts of Albizia saman in order to further establish its effectiveness against Aedes aegpyti.