Behavioural activities and chemical composition of fresh leaf essential oil of Plectranthus aegyptiacus from Southwest Nigeria in mice
1 Department of Pharmacology, Faculty of Pharmacy.
2 Department of Pharmacognosy, Obafemi Awolowo University, Ile-Ife, 220005, Osun State, Nigeria.
3 Department of Chemical and Physical Sciences, Faculty of Natural Sciences, Walter Sisulu University, NMD Campus, Mthatha, South Africa.
4 Department of Chemistry, Faculty of Science and Agriculture, University of Fort Hare, Alice, South Africa.
Research Article
GSC Biological and Pharmaceutical Sciences, 2021, 14(02), 064-076.
Article DOI: 10.30574/gscbps.2021.14.2.0030
Publication history:
Received on 15 January 2021; revised on 05 Februay 2021; accepted on 08 Februay 2021
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.
Keywords:
Acute toxicity; Carvacrol; Essential oil; Novelty-induced behavior; Plectranthus aegyptiacus
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