Georges Piombo

Bioefficacy of essential and vegetable oils of Zanthoxylum xanthoxyloides seeds against Acanthoscelides obtectus (Say) (Coleoptera: Bruchidae).

Experiments were conducted in the laboratory to evaluate the bioefficacy of essential and vegetable oils of Zanthoxylum xanthoxyloides (Rutaceae) against Acanthoscelides obtectus (Coleoptera: Bruchidae). The chemical composition of the essential oil and the fatty acid composition of the vegetable oil extracted from the seeds of Z. xanthoxyloides were determined. The insecticidal activities of these oils and the associated aromatized clay powder were evaluated against A. obtectus. Both oils were strongly repellent (100% repellency at 0.501 μl/cm² essential oil and 3.144 μl/cm² vegetable oil) and highly toxic (LC₅₀ = 0.118 μl/cm² for essential oil) to this beetle after contact on filter paper. The vapors of the essential oil were highly toxic to adult insects (LC₅₀ = 0.044 μl/cm³), and the aromatized powder made from clay and essential oil was more toxic (LD₅₀ = 0.137 μl/g) than the essential oil alone (LD₅₀ = 0.193 μl/g) after 2 days of exposure on a common bean. Both oils greatly reduced the F₁ insect production and bean weight loss and did not adversely affect the bean seed viability. In general, the results obtained indicate that these plant oils can be used for control of A. obtectus in stored beans.

Toward the synthesis of pyroglutamate lauroyl ester: biocatalysis versus chemical catalysis

The synthesis of dodecyl pyroglutamate (or pyroglutamate lauroyl ester) was achieved in a two-step process involving a pyroglutamic acid alkyl ester intermediate. The reaction was carried out either by lipase or by chemical catalysis using ion exchange resin. Among the various tested lipases, the one from Candida antarctica B gave the best results allowing 73% formation of the desired ester after 6 h. Comparing the efficiency of this latter lipase with the one of Amberlyst IR120H resin in catalyzing this reaction, the biocatalyst gave a molar yield of pyroglutamate lauroyl ester of 79% compared to 69% when using the ion exchange resin starting with 1.04 mmol substrate in each case.