Assessing Bioactive Metabolite Contents, Mosquito Larvicidal, and Anti-Plasmodial Activities of Neoscona adianta Spider Extracts.
Abstract:
Despite extensive control efforts, mosquitoes continue to transmit serious human diseases, causing millions of deaths annually and developing resistance to chemical insecticides, leading to increased vectorial capacity. This problem is compounded by the re-emergence of drug resistance in mosquito-borne diseases, particularly malaria. To address this issue, the present study aimed to evaluate the larvicidal potency and antiplasmodial efficacy of crude and fractionated extracts from the spider species Neoscona adianta.
Standard procedures were employed to assess the zoochemical components of the crude and fractionated spider extracts. Larvicidal potency testing was conducted following the World Health Organization (WHO) standard protocol with slight modifications. Graded concentrations (ranging from 0.2 to 2.0 mg/kg) of the crude and fractionated spider extracts were tested against 25 batches of healthy 4th instar larvae of the Culex mosquito species, and larval mortality was recorded after a 24-hour exposure period. Additionally, acute oral toxicity testing was performed to determine the safe oral dose of the crude extract.
The antiplasmodial activities of the crude extract and fractions were bio-assayed against established infections in chloroquine-sensitive Plasmodium berghei infected mice. The results indicated the presence of zoochemicals, including flavonoids, tannins, saponins, alkaloids, steroids, total phenols, and terpenoids, in both the crude extract and fractions of the spider. In the larvicidal bio-assay, both crude and fractionated extracts exhibited dose and concentration-dependent larvicidal potency. Notably, the ethyl acetate and n-hexane fractions displayed significantly higher (P<0.05) larvicidal activities compared to the crude methanol extract, with only the ethyl acetate and n-hexane fractions achieving 100% mortality at the highest tested concentration (2.0 mg/kg). The n-hexane fraction showed the best larvicidal activity with an LC50 of 0.46 mg/L, followed by ethyl acetate with an LC50 of 0.94 mg/L.
The acute oral toxicity testing confirmed that the spider extract is safe for oral administration, with an LC50 greater than 5000 mg/kg of body weight. Furthermore, the crude and fractionated extracts demonstrated dose-dependent antiplasmodial activities, with the peak activity observed in the group of mice treated with 600 mg/kg of body weight of the crude extract. Although the crude and fractions did not ameliorate the fall in PCV (packed cell volume), they promoted body weight change and extended survival time.
These findings support the traditional medicinal use of spider extracts in folkloric medicine and suggest that this spider species contains bio-active compounds that could be developed as potent antimalarial drugs and effective bio-pesticides against mosquito vectors.
Assessing Bioactive Metabolite Contents, Mosquito Larvicidal, and Anti-Plasmodial Activities of Neoscona adianta Spider Extracts.