Mosquito is well-known vector in transmitting various dangerous diseases including, Dengue Hemorrhagic Fever (DHF). Based on WHO data in 2018, 390 million cases of DHF infection occurred. Aedes aegypti and Aedes albopictusare the main vectors of this disease. These two types of mosquitoes are also known as vectors for various diseases such as chikungunya, filariasis, yellow fever, encephalitis and zika infection.
The habitat of Aedes mosquito is clean water. This mosquito-borne disease is difficult to eradicate because there are always water reservoirs in the environment. People who have artificial or natural water reservoirs such as bathtubs, ponds, rain collectors, flower vases, used tires, bamboo that are not cut to the nodes, have a great potential for contracting diseases that can be spread by Aedes.
So far, adult mosquito eradication is still focused on using synthetic insecticides such as fogging and abate. Vector control can be carried out at all stages of the life cycle of mosquitoes. Controlling larval stage is actually more effective than the adult stage because the larvae are relatively immobile, immature, so they cannot produce eggs and more concentrated.
Spraying with synthetic insecticides repeatedly in the long term and the use of abate cause resistance to vectors and environmental pollution. Synthetic insecticides are chemical compounds and difficult to degrade naturally. Synthetic insecticides can kill and reduce the reproductive capacity of non-target organisms such as birds and fish. In addition, synthetic insecticides can affect the health of humans or livestock.
The utilization of natural components from plants as larvicides is expected to be able to reduce cases of disease caused by vectors without causing negative impacts. Larvicides derived from plants generally have no side effects, are safer for humans, available in large quantities, and degraded naturally, so they don’t pollute the environment.
In this study, we explored the Brotowali plant, which has the scientific name Tinospora crispa. Brotowali is a plant that has been used by Indonesians as traditional medicine. Brotowali has anti-inflammatory, antioxidant, anti-parasitic, and anti-diabetic properties. We can find various secondary metabolites in this plant, namely in the form of alkaloids, terpenoids. lignans, sterols, and flavonoids. Other plants that contain secondary metabolites like this are proven to be able to become biolarvicides for Aedes. The part of the plant that we focus on is the leaf.
We carried out phytochemical and GCMS tests to ensure the content of secondary metabolites in the Brotowali leaf extract. The phytochemical test provides qualitative data on the presence or absence of secondary metabolites in the Brotowali extract, while GCMS will provide chemical compounds data found in this extract. Biolarvacidal tests of LC50 and LC90, which are lethal concentrations that can kill 50% and 90% of the larvae population, were carried out to see the ability of this extract to kill larvae.
The phytochemical test showed positive results only for the terpenoid/steroid compounds. Terpenoids are chemical compounds that are also found in natural repellents such as star fruit and oranges. Terpenoids act as antifeedants preventing larvae from eating. If the terpenoids enter the larva’s body, the feeding process will be disrupted. Terpenoids block the food taste receptors. Larvae cannot recognize their food and cannot reach a certain weight to enter the next instar. These terpenoids also have a similar function to adrenaline invertebrates. This compound can block octopaminem, a neurotransmitter in larvae.
The GCMS test showed three dominant compounds in the Brotowali leaf extract that have biolarvicide potential. α-Methylphenylethylamine is classified as an amphetamine. High concentration of amphetamine can cause abnormalities in the respiratory organs and muscles. Benzeneetahmine belongs to the alkaloid class. This component act as a poison and destroy the gut tissue of the larvae. Meanwhile, Methyl L-alaninate is an amino acid. Although it has a positive effect in the cell signaling process, it causes oxidative stress if the concentration is too high.
The results of the biolarvicide test showed the LC50 value at 1205.092 ppm and LC90 at 4104,596 ppm. From this data, brotowali leaf extract can be categorized as biolarvicide because it has a toxic effect. Larval mortality was also observed after 24 hours of exposure to the extract, and the results showed 98.33% of larvae died.
Thus, it can be concluded that Brotowali leaves can be used as an effective biolarvicide candidate to reduce the population of Aedes aegypti larvae. Alkaloids and terpenoids have the potential to become bioactive compounds in killing larvae. We hope that the results of this study give a safer and more environmentally friendly alternative to chemical insecticides.
Author: Manikya Pramudya
Details of the research can be viewed here:
http://www.envirobiotechjournals.com/article_abstract.php?aid=10420&iid=301&jid=3
