Volatile Oil Constituents, Bioactivity and Formulations of Essential Oil from Psidium guajava

Abstract

With the availability of myriad of plants having insecticidal activity, the issue of toxicity while using synthetic compounds to eradicate pests would be resolved. Therefore, the search for and formulations of insecticidal plants have grown remarkably, in recent years. It is on this premise that this work sought to characterize, evaluate the bioactivity and formulations of essential oil of Psidium guajava (PG) for insecticidal activity. Volatile oil of from PG was characterized using Gas Chromatography-Mass Spectrometry to identify the compounds present. Filter paper and anti-feedant methods were used to test the oils for insecticidal activities against adult Callosobruchus maculatus. The releasing profiles of the volatile oil formulations were observed for 15 days at 3 days interval using bentonite and kaolin as carriers at different concentrations (10, 20 30 40 and 50 µl). Antimicrobial activities of the volatile oil were also carried out on some bacterial and fungus pathogens using standard methods. From the results, forty-nine (49) compounds were identified in PG volatile oil with α-Limonene (29.55 %), γ-cadinene (9.61 %), caryophyllene (9.44 %), nerolidol (7.19 %) and viridiflorol (4.29 %) as major components. After 6 hours and 24 hours of filter paper and anti-feedant test, the volatile oil toxicity results showed that the percentage mortality of Callosobruchus maculatus increased significantly (p > 0.05) with increase in concentration. Oil formulation results showed that the efficacies and the insecticidal activity decreased with time. Antimicrobial studies showed that the extracted oil inhibited the growth of tested organisms at different zones of inhibition.