Elaboration of Biocide from Azadirachta indica (Neem) Leaves, Carica papaya Leaves, and Corn Starch Extracts for the Purpose of Wood Protection

Abstract

Azadirachta indica leaves, commonly known as neem leaves, and Carica papaya leaves, commonly known as pawpaw leaves, are both rich in active compounds with potential insecticidal and fungicidal abilities. The objective of this work was to formulate a biocide for wood control. Extractions were done by simple maceration of neem and papaya leaf powder using ethanol/distilled water (80:20). Phytochemical screening was then carried out to determine the chemical composition of the leaf extracts. Determination of total polyphenol content was done using the Folin-Ciocalteu method. A mixture design was used to optimize the biocide formulation. Antifungal and insecticidal activities were evaluated using the pit method and the mass-loss method, respectively. The results show that extractions of neem and papaya leaf powder yielded 77.78% and 57.71%, respectively. Their total polyphenol contents were 27.5±1.3 and 17.3±0.9 mg EAG/g powder, respectively. The amylose content of corn starch was 29.45±0.38%, which conferred a sticky property. Optimization of the biocide formulation yielded the following optimal composition: 10% extracts, 10% corn starch glue, and 80% water. Evaluation of antifungal activity showed that Mucor sp. was more sensitive than Rhyzopus sp. to the formulated biocide, with inhibition diameters of 10 and 8 mm, respectively. Evaluation of insecticidal activity with doses of 15 ml and 20 ml per 200 g of wood did not result in any weight loss. Therefore, the formulated biocide could thus constitute a green, non-toxic alternative to conventional chemical products for wood termite control.