Composition and Larvicidal Activity of the Oil of Dizygostemon riparius (Plantaginaceae), a New Aromatic Species Occurring in Maranhão, Brazil.

Dizygostemon riparius (Plantaginaceae) is a new aromatic herbaceous species occurring in Maranhão State, Brazil. It is used as flavorings to remove domestic animal parasites and preventing mosquitoes. GC and GC/MS were used to analyze its essential oil, and a larvicidal bioassay was performed against Aedes albopictus larvae, a vector of arboviruses in Brazil. endo-Fenchyl acetate, endo-fenchol, (E)-caryophyllene, and caryophyllene oxide were the oil's primary constituents, totalizing 88.0 %. The two morphotypes of D. riparius, with purple and white flowers, did not present a significant difference in the oils' composition. From a chemotaxonomic point of view, D. riparius oil showed some similarities with other oils of Plantaginaceae, suggesting (E)-caryophyllene and caryophyllene oxide as possible chemical markers. The oil larvicidal action displayed the lowest and highest mortality percentage at 50 mg/L (2.0 %) and 600 mg/L (88.0 %). The fenchyl acetate and fenchol standards showed a lower and higher mortality percentage at a concentration of 300 mg/L (42.0 % and 26.0 %) and 900 mg/L (96.0 % and 98.0 %), respectively. The present study results with the D. riparius oil point to a new bioproduct with significant larvicidal activity.