The application of 1,8-cineole, a terpenoid oxide present in medicinal plants, inhibits castor oil-induced diarrhea in rats

Figures & data

Figure 1. Chemical structure of 1,8-cineole which is the principal constituent of the many medicinal plant essential oils.

Table 1. Acute oral toxicity of 1,8-cineole in rats.

		Effects
Treatment (g/kg)	D/T	Mortality latency (h)	Symptoms of toxicity
10	0/3	–	None
100	0/3	–	None
600	0/3	–	Ataxia, hypoactivity, labored respiration, convulsion, recovery after 185 ± 5 min
1000	2/3	>6, <15	Ataxia, hypoactivity, labored respiration, head tics, body tremor, convulsion, paddling, flaccid paralysis, recumbencey, unresponsive to writhing test, recovery after 24 ± 5 min
1600	1/3	>2, <10	Ataxia, hypoactivity, labored respiration, head tics, body tremor, convulsion, flaccid paralysis, recumbencey, unresponsive to writhing test, recovery after 73 ± 5 min
2900	3/3	>2, <3	Ataxia, hypoactivity, labored respiration, body tremor, convulsion, paddling, flaccid paralysis, recumbencey, unresponsive to writhing test

The 1,8-cineole, dissolved in Tween 80 (2%) was administered as single oral doses to six groups of three rats. All animals were carefully examined for adverse effects (behavioral changes and mortality) for 14 d. Symptoms of toxicity are described for a group; D/T, dead/treated rats; latency, time to death after the dose; none, no toxic symptom during the observation period.

Table 2. Effect of 1,8-cineole on normal gastrointestinal transit in rat.

Group dose (mg/kg)	Peristaltic index (%)	% Inhibition
Vehicle control (Tween 2%)	64.00 ± 2.08	–
Atropine (0.1)	38.50 ± 2.95*	39.84
1,8-Cineole (120)	57.00 ± 1.41	10.93
1,8-Cineole (80)	60.75 ± 1.25	5.07
1,8-Cineole (60)	57.25 ± 3.25	10.54
1,8-Cineole (20)	55.50 ± 2.21	13.28
1,8-Cineole (80) + atropine (0.1)	53.25 ± 1.37*	16.69

Values are expressed as mean ± SEM (n = 6).

*p < 0.05 versus vehicle control.

Table 3. Effect of the 1,8-cineole on diarrhea onset and the time course of diarrhea induced by castor oil in rats.

	Diarrhea onset	Animals with diarrhea (%)
Treatment (mg/kg)	(min)	1 h	2 h	3 h	4 h
Vehicle control (Tween 2%)	103.66 ± 8.46	0	100	100	100
1,8-Cineole (120)	142 ± 6.08*	0	0^a	100	83.33
1,8-Cineole (20)	117 ± 3.66	0	100	83.33	83.33
Loperamide (3)	>240*	0	0^a	0^a	0^a

Values are expressed as mean ± SEM and the percentage of animal with diarrhea (n = 6).

^ap < 0.05 versus vehicle control (Chi-square test). *p < 0.05 versus vehicle control (ANOVA followed by the Dunnett test).

Table 4. Antidiarrheal activity of 1,8-cineole on the diarrhea parameters that induced by castor oil in rats.

		1 h			2 h			3 h			4 h
Treatment (mg/kg)	Onset time of diarrhea (min)	F. no.^a	F.W.^a	D.S.^a	F. no.	F.W.	D.S.	F. no.	F.W.	D.S.	F. no.	F.W.	D.S.
Vehicle control (Tween 2%)	103.66 ± 20.73	0.00	0.00	0.00	2.66 ± 0.33	2.35 ± 0.33	8.66 ± 0.88	2.66 ± 0.21	1.90 ± 0.09	5.33 ± 0.33	2.33 ± 0.21	1.10 ± 0.03	4.33 ± 0.61
1,8-Cineole(120)	142.33 ± 6.08^a	0.00	0.00	0.00	0.00*	0.00*	0.00*	2.83 ± 0.47	1.08 ± 0.79	6.16 ± 0.30	1.83 ± 0.40	0.86 ± 0.19	3.50 ± 1.20
1,8-Cineole (20)	117.66 ± 3.66	0.00	0.00	0.00	3.66 ± 0.21*	3.56 ± 0.20*	10 ± 0.57	3.83 ± 1.35	3.13 ± 0.66*	6.33 ± 1.45	3.16 ± 0.87	2.63 ± 0.67*	5.83 ± 1.92
Loperamide (3)	>240*	0.00	0.00	0.00	0.00*	0.00*	0.00*	0.00*	0.00*	0.00*	0.00*	0.00	0.00*

^aFecal numbers (F. no.), fecal weight (F.W.), diarrhea score (D.S.).

Values are expressed as mean ± SEM (n = 6).

*p < 0.05 versus vehicle control.

Table 5. Effect of 1,8-cineole on castor oil-induced enteropooling in rat.

Treatment (mg/kg)	Fluid volume (mL)	% Inhibition
Vehicle control (Tween 2%)	4.25 ± 0.22	–
Distilled water (10 mL/kg)	3.79 ± 0.40^a	10.82
1,8-Cineole (120)	2.38 ± 0.15^b	44.08
1,8-Cineole (20)	3.80 ± 0.50^a	10.58
Loperamide (3)	1.83 ± 0.16^c	56.94

Values are expressed as mean ± SEM (n = 6). ^ap < 0.05, ^bp < 0.01, and ^cp < 0.001 versus vehicle control.