Abstract
Objectives: This study determined the chemical composition of essential oil obtained from fresh leaf of Plectranthus aegyptiacus, and evaluated it for novelty-induced behavioural (NIB) and determine its mechanism(s) of action in mice. Methods: The oil was hydro-distillated, and analyzed using gas chromatography-mass spectrometry. The effects of the oil (50, 100 and 150 mg/kg; i.p., n=6) on novelty-induced behavioural was assessed using open field test and head dipping on hole board. Probable mechanism(s) were evaluated using antagonists: flumazenil, naloxone and cyproheptadine at 2 mg/kg each, atropine and yohimbine at 5 mg/kg and 1 mg/kg respectively. Key Findings: The LD50 values obtained were 2154 and 490 mg/kg for oral and intraperitoneal routes respectively. The oil (50, 100 and150 mg/kg) significantly (p<0.05, 0.01 and 0.01) inhibited all NIB and head dips. Flumazenil significantly (p<0.05) reversed the effect of the oil on NIB; atropine, naloxone and cyproheptadine significantly (p<0.01, 0.01 and 0.001) potentiated inhibitory effect on NIB respectively, while yohimbine showed no significantly effect. The analyzed oil showed 61 compounds, and the major compounds were carvacrol, germacrene-D, p-cymene and [1,1'-Bicyclopentyl]-2,2'-diol. Conclusions: The study concluded that the oil possessed central nervous system depressant activity, which could be mediated mainly through augmentation of GABAergic neurotransmission, while cholinergic-(muscarinic), adrenergic and serotonergic pathways may be involved.
Highlights
The use of plants for treating ailments and diseases is as old as human species, it is difficult to point to an exact time
Objectives: This study determined the chemical composition of essential oil obtained from fresh leaf of Plectranthus aegyptiacus, and evaluated it for novelty-induced behavioural (NIB) and determine its mechanism(s) of action in mice
The study concluded that the oil possessed central nervous system depressant activity, which could be mediated mainly through augmentation of GABAergic neurotransmission, while cholinergic-(muscarinic), adrenergic and serotonergic pathways may be involved
Summary
The use of plants for treating ailments and diseases is as old as human species, it is difficult to point to an exact time. Plectranthus aegyptiacus, synonym P. tenuiflorus (Vatke) Agnew, differing in their essential oil compositions [4] is widely spread in tropical Africa, including Nigeria, where it is commonly known as Efinrin-Oyinbo and Kpo-Oyibo among the Yoruba and Epie speaking people of southern Nigeria respectively. Several studies have identified diverse chemical compounds in the essential oil of Plectranthus aegyptiacus and notable ones include myrcene, limonene, camphor, borneol, terpinen-4-ol, α-terpineol, α-cubebene, β-cubebene, caryophyllene oxide, β-caryophyllene among others [7,8,9], reported are octen-3-ol, α-terpinene, terpinene-4-ol, γ-terpinene, α-terpinyl acetate, linalool, carvacrol, β-bourbonene, β-elemene, αgurjunene, γ-elemene, aromadendrene, germacrene D, γ-muurolene and α-amorphene among others as constituents of the plant leaf [10]. The chemical composition of the oil used was not analysed this study aimed at evaluating the oil for behavioural activities, determine its mechanism(s) of action in mice as well as characterizing its chemical constituents
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