Chemical composition and insecticidal properties of essential oils of Piper septuplinervium and P. subtomentosum (Piperaceae).

Essential oils of Piper subtomentosum (leaves and inflorescences) and Piper septuplinervium (aerial parts) were analyzed by GC-MS; sixty-three compounds were determined, representing 92.0%, 86.9 %, and 91.8 % of the total relative oil composition of the leaves, inflorescences, and aerial parts, respectively. The most abundant component in the aerial parts and inflorescence oils was α-pinene (27.3%, 21.0%, respectively), and δ-cadinene was the main component of the leaf oil. Insecticidal activity of the essential oils were determined on the Spodoptera frugiperda second instar larvae; the essential oil from the aerial parts of P. septuplinervium was the most active against insect pests (LC50= 9.4 μL/L of air). Statistical analysis by direct Pearson correlation showed that the insecticidal activity of the essential oils was primarily due to camphene and α- and β-pinene. The effect of the oils on the insect life cycle was also evaluated, and in some cases, a delay in growth and inhibition of the oviposition in the females were observed.