Neuropharmacological profile and chemical analysis of fresh rhizome essential oil of Curcuma longa (turmeric) cultivated in Southwest Nigeria

Abstract

Background: Curcuma longa (turmeric) is commonly used as spice and also used to treat fever, cough and febrile convulsions in Nigeria. This study determined the chemical composition of the essential oil of C. longa and evaluated its neuropharmacological activity in mice.

Methods: Essential oil of C. longa (EOCL) fresh rhizome was obtained by hydrodistillation and its chemical composition determined by GC-MS. Acute toxicity (LD₅₀) profile of the essential oil was determined orally (p.o.) and intraperitoneally (i.p.); and the EOCL (50-200 mg/kg, i.p.) was evaluated for its behavioural, anxiolytic, sedative and anticonvulsant activities using appropriate models in Albino mice (Vom Strain, Jos, Nigeria).

Results: Analysis of the oil showed the presence of 23 compounds with turmerone (35.9%) being the major component. The LD₅₀ values obtained for the mice were 2154 mg/kg, p.o., and 693 mg/kg, i.p. The EOCL (50-200 mg/kg, i.p.) caused significant (p < 0.01) inhibition of rearing {F_(4,20) = 9} and locomotor {F_(3,16) = 42} activity; decreased head dips in hole board {F _(4,20) = 4}; increased the time spent in the open arms of the elevated pus maze {F _(4,20) = 9}; prolonged total sleeping time {F _(4,20) = 21} induced by ketamine injection, and protected mice against pentylenetetrazol-induced convulsions.

Conclusion: The major component of the essential oil of this C. longa species was turmerone; the oil was slightly toxic orally but moderately toxic intraperitoneally in mice; exhibited significant anxiolytic, sedative and anticonvulsant activities in mice.

Keywords: Acute toxicity; Anticonvulsant; Behavior; Essential oil; Sedative; Turmeric; Turmerone.

Graphical abstract

Fig. 1

Chromatogram of essential oil of fresh Curcuma longa rhizome.

Fig. 2

Effects of the EOCL on rearing (Panel A) and locomotor activity (Panel B) in mice. Each bar represents mean ± SEM. VEH, EOCL and DZM represent vehicle (5% Tween 80), essential oil of C. longa and diazepam respectively. N = 5. *p < 0.01; compared to control group (ANOVA, Dunnett’s test).

Fig. 3

Effect of the EOCl on head-dipping behaviour on the hole board test. Each bar represents mean ± SEM. VEH, EOCL and DZM represent vehicle (5% Tween 80), essential oil of C. longa and diazepam respectively. N = 5. *p < 0.01, compared to control group, (ANOVA, Dunnett’s test).

Fig. 4

Effect of the EOCL on percentage number of entries into open arms (Panel A) and percentage time spent on open arms (Panel B) of the epm. VEH, EOCL and DZM represent vehicle (5% Tween 80), essential oil of C. longa and diazepam respectively. *p < 0.05, **p < 0.01; significant compared to vehicle group (ANOVA, Dunnett’s test).

Fig. 5

Effect of the EOCL on ketamine-induced sleep latency (Panel A) and total sleeping time (Panel B) in mice. VEH, EOCL and DZM represent vehicle (control), essential oil of C. longa and diazepam respectively. N = 5. *p < 0.05 compared to control; **p < 0.01compared to other groups (ANOVA, Dunnett’s test).