Biomonitoring the &i&Vitex gardneriana&/i& Shauer (Lamiaceae) Toxic Effects to Shed Light on Bioactive Compounds against a Major Coconut Pest Mite

摘要

The coconut mite, Aceria guerreronis Keifer (Acari: Eriophyidae), is a major pest of coconut plantations (Cocos nucifera L.) worldwide. Here, we conducted a bioguided phytochemical approach using toxicity and repellency bioassays of nonpolar extract and its fractions of Vitex gardneriana Schauer (Lamiaceae) leaves to this pest. Nonpolar crude extract was fractionated by column chromatography using solvents with increased polarity and binary mixtures, resulting in five semipurified groups. The biomonitor ing bioassay provided active fractions and led to the isolation and characterization of the bioactive compound squalene, a biosynthetic precursor of 20-hydroxyecdysone, which plays an important role in plant defense against arthropods. The LC_(50) of the crude extract of V . gardneriana for A . guerreronis was estimated to be 0.185 mg·mL~(-1) and LC_(80) = 4.123 mg·mL~(-1). Also, the extract was highly repellent to this pest for up to 24 h. The fractions of V . gardneriana , and also squalene, caused mortality to A . guerreronis . The potential of V . gardneriana fractions/squalene as biopesticides for controlling A . guerreronis in coconut plantations is discussed herein.