title: Chemical composition, toxicity and antioxidant activities of essential oils of stem bark of Nigerian species of guava (Psidium guajava Linn.).
abstract: Essential oil from the stem bark of Nigerian species ofPsidiumguajavaof the family Myrtaceae was obtained by hydro-distillation using an all-glass Clavenger apparatus. GC and GC/MS analysis were carried out on the essential oil and was found to contain 62 compounds constituting 99.98 % of the total oil composition. The principal constituents are hydrocarbons, amines, amides and esters with 3,6-dioxa-2,4,5,7-tetraoctane,2,2,4,4,5,5,7,7-octamethyl (11.67 %) and cyclononane (10.66 %) dominating the total essential oil. Brine shrimp lethality test was carried out to determine the toxicity of the oils to living organisms (shrimps). LC50value (µg/ml) of 1.0009 obtained showed that the essential oil ofP.guajavastem bark was toxic. The antioxidant property of essential oil was investigated by measuring the decrease in absorption at 517 nm of 1,1-diphenyl-2-picrylhydrazyl radical (DPPH) in a UV/visible spectrophotometer. The oil showed better activity as a radical scavenger than α-tocopherol. The oil activity was 71.83 % at 0.2 mg/ml and the absorption is stoichiometric with respect to the number of electron taken up. Thus, the results of this study showed that the essential oil fromP.guajavawas not only toxic; it possessed antioxidant activity, which could exert beneficial actions against pathological alterations caused by the presence of highly reactive free radicals. The toxicity of the oil can be taken advantage of in the therapy of diseases involving cell or tumor growth.
authors.affiliation: Department of Botany and Microbiology, University of Ibadan, Nigeria.
authors.forename: Taiye R
authors.initials: TR
authors.lastname: Fasola
authors.affiliation: Natural products/Medicinal Chemistry Unit, Department of Chemistry, University of Ibadan, Nigeria.
authors.forename: Ganiyat Kehinde
authors.initials: GK
authors.lastname: Oloyede
authors.affiliation: Department of Botany and Microbiology, University of Ibadan, Nigeria.
authors.forename: Babalola S
authors.initials: BS
authors.lastname: Aponjolosun
keywords: 1,1-diphenyl-2-picrylhydrazyl; GC/GC-MS; Psidium guajava; antioxidant; essential oils; toxicity