Analytical methods to assess larvicidal compounds in extracts from Dendranthema x grandiflorum (Ramat.) Kitam. residues

Flowers from Dendranthema x grandiflorum (Ramat.) Kitam. are grown in Brazil for floristic trade, and residues from different cultivars are generated, containing flowers, leaves and stems. These residues can be used to produce larvicidal products. To confirm this hypothesis, 27 dichloromethane extracts were produced from Dendranthema x grandiflorum agricultural residues. All were analyzed by GC–MS and FT-ICR MS with two different ionization sources, APCI and ESI. The spectra and chromatograms were converted to matrices, which were used as input for PCA analyses. Simultaneously, the extracts at concentrations of 5 and 15 ppm were submitted to larvicidal assays on Aedes aegypti larvae, the etiological agent of dengue, chikungunya and zika diseases. High larvicidal activity (larvae mortality > 80%) was found for 14 samples, medium larvicidal activity (70% > larvae mortality > 40%) for 4 samples and low larvicidal activity (larvae mortality < 40%) for 9 samples. The PCA graph for GC–MS chromatograms furnished three groups (GC1, GC2 and GC3). Group GC2 included nine of the highly active samples, and Group GC3 included seven of the less active ones. Similarly, three clusters were formed when ESI (−) FT-ICR MS data were used. Groups GC1 and GC2 included most of the highly active samples. The APCI (+) FT-ICR MS data, however, did not discriminate groups by biological activity. Such data show triterpenes and fatty acids as the classes of natural substances that most contributed to the discrimination of the samples. The highly active samples either had a fatty acid/triterpene ratio between 1 and 4 (most) or had a high concentration of triterpenes. The data suggest that triterpenes are the plant's larvicidal molecules and that fatty acids act as synergistic agents.