The essential oil and the aqueous and ethanolic extracts obtained from the aerial parts of Pelargonium graveolens cultivated in Morocco were studied for their antioxidant and insecticidal activity against rice weevils (Sitophylus oryzae). The total phenolic content of the extracts was determined by a spectrophotometric method and the phenolic compounds were extensively characterized by HPLC-PDA/ESI-MS. To evaluate antioxidant potential, three in vitro assays were used. In the DPPH test, the ethanolic extract was the most active, followed by the aqueous extract and the essential oil. In the reducing power assay, excellent activity was highlighted for both extracts, while in the Fe2+ chelating activity assay, weak activity was observed for both the essential oil and the ethanolic extract and no activity for the aqueous extract. Concerning insecticide activity, the toxicity of the essential oil and the extracts was tested against rice weevils; the lethal concentrations LC50 and LC99 were determined, as well as the lethal time required for the death of 50% (LT50) and 99% (LT99) of the weevils. The essential oil had the highest activity; 100% mortality of S. oryzae was observed around 5, 9, and 8 days for the essential oil and the aqueous and ethanolic extracts, respectively.
Keywords: HPLC-PDA/ESI-MS; Pelargonium graveolens L’Hér.; Sitophilus oryzae L.; antioxidant activity; botanical insecticide; phenolic compounds.