Extraction of botanical pesticides from Pelargonium graveolens using supercritical carbon dioxide

• Supercritical fluids extraction of Pelargonium graveolens leaves was optimized.
• Chemical composition and pesticidal activity of CO2 extracts were evaluated.
• Acute toxicity and antifungal activity were dependent on volatile concentration.
• Synergistic effect of volatiles and non-volatiles was observed in the CO2 extracts.

Pelargonium graveolens is a valuable source of biologically active compounds and a promising botanical pesticide. In this study, supercritical fluid extraction (SFE) of Pelargonium leaves was optimized to improve the extraction yields, selectivity and pesticidal activity under different operational conditions (pressure 9–30 MPa, temperature 40 and 50 °C). The composition and pesticidal activity of the CO2 extracts were compared with the isolates obtained by maceration and hydrodistillation. GC–MS and GC–FID were used to determine the chemical composition of the isolates. The insecticidal activity (acute and chronic toxicity, antifeedancy) of the isolates was measured on larvae of Spodoptera litoralis. The antifungal activity was evaluated as the inhibition effect on the growth of model pathogenic and toxinogenic fungi (Fusarium oxysporum, Penicillium expansum, Aspergillus fumigatus). The highest yield of CO2 extract was 44.5 mg gplant−1 at 30 MPa, 40 °C and the maximum concentration of the volatiles in extract was 56% w/w at 9 MPa, 50 °C. The insecticidal activity of isolates differed according to the type of test: CO2 extracts obtained at 9 MPa, 50 °C and at 12 MPa, 40 °C exhibited the highest chronic toxicity (LD50 = 6 μg) and antifeedancy (ED50 = 95 μg cm−2), respectively. The essential oil obtained by hydrodistillation, with the yield of 8.5 mg gplant−1 showed the strongest acute toxicity (LD50 = 28 μg). The antifungal activity of isolates increased as the volatile concentration in isolates increased. Results suggest that CO2 extracts of P. graveolens can be suitable substitutes to the essential oil in the use as botanical pesticides.