Protective activity of geraniol against acetic acid and Helicobacter pylori- induced gastric ulcers in rats

Abstract

Geraniol, an active constituent of rose and palmarosa essential oils, possesses several pharmacological properties, including antioxidant, antibacterial and antiulcer activity. Geraniol was therefore investigated for its antiulcer and anti-Helicobacter pylori activity in rats. Ulcers were induced by injecting acetic acid into the sub-serosal layer of the stomach followed by orogastric inoculation of H. pylori for 7 days. Geraniol (15 and 30 mg/kg), vehicle and a standard drug combination (amoxicillin, 50 mg/kg; clarithromycin, 25 mg/kg and omeprazole, 20 mg/kg) were administered twice daily for 14 days. All the parameters were measured at the end of treatment. The ulcer index was significantly (P < 0.05) lowered in geraniol and standard drug-treated rats as compared to the H. pylori control group (4.13 ± 0.43). Treatment with geraniol (30 mg/kg) significantly (P < 0.01) increased the gastric pH along with a reduction in total acidity and gastric juice volume. Geraniol significantly (P < 0.05) attenuated the myeloperoxidase activity and augmented the total glutathione level in gastric mucosa. The extent of damage in the stomach was measured using a histopathological score. The score in H. pylori control, geraniol (30 mg/kg) and standard drugs was 9, 3.5 and 2.0 respectively. In the rapid urease test, treatment with geraniol (30 mg/kg) and the standard drugs produced a 33% and 67% cure respectively from H. pylori infection. Further, the reduction in bacterial load in the gastric mucosa was confirmed using modified Giemsa staining. Geraniol was observed to exhibit significant antiulcer and anti-H. pylori activity in a rodent model.

Keywords: Antiulcer; Geraniol; Glutathione; Helicobacter pylori; Myeloperoxidase.

Graphical abstract

Fig. 1

Gross morphological observation of stomach in H. pylori and acetic acid-induced ulcer in rats (magnification = 1.3×). A: Normal control group having intact stomach with normal morphology of the stomach; B: Ulcer control group without H. pylori showing extensive damage to gastric mucosa with sever ulceration and haemorrhage (red arrow) condition; C: Ulcer control group with H. pylori showed extensive mucosal damage and many ulcerated lesions with haemorrhage; D: Geraniol (15 mg/kg, b. i.d.) treated rats showed moderate ulcer lesions with less haemorrhage; E: Geraniol (30 mg/kg, b. i.d.) treated rats showed mild injuries and ulcer lesions without haemorrhage; F: Standard drug (amoxicillin, 50 mg/kg; clarithromycin, 25 mg/kg and omeprazole, 20 mg/kg, b. i.d.) treated rats showed mild injuries and ulcer lesions without haemorrhage.

Fig. 2

Effect of geraniol on myeloperoxidase activity (mU/ml) per gm of gastric tissue of H. pylori and acetic acid-induced ulcerated rats. ^$P < 0.05 vs normal control; ^$$P < 0.01 vs normal control; *P < 0.05 vs ulcer control with H. pylori; **P < 0.01 vs ulcer control with H. pylori. NC: Normal control group; UC: Ulcer control group without H. pylori; UC with H. pylori: Ulcer control group with H. pylori; Ger_15 mg/kg: Geraniol (15 mg/kg, b. i.d.); Ger_30 mg/kg: Geraniol (30 mg/kg, b. i.d.); Std. Drugs: Standard Drug (amoxicillin, 50 mg/kg; clarithromycin, 25 mg/kg and omeprazole, 20 mg/kg, b. i.d).

Fig. 3

Effect of geraniol on total glutathione (μM) per gm of gastric tissue in H. pylori and acetic acid- induced ulcerated rats. ^$P < 0.05 vs normal control; *P < 0.05 vs ulcer control with H. pylori. NC: Normal control group; UC: Ulcer control group without H. pylori; UC with H. pylori: Ulcer control group with H. pylori; Ger_15 mg/kg: Geraniol (15 mg/kg, b. i.d.); Ger_30 mg/kg: Geraniol (30 mg/kg, b. i.d.); Std. Drugs: Standard Drug (amoxicillin, 50 mg/kg; clarithromycin, 25 mg/kg and omeprazole, 20 mg/kg, b. i.d.).

Fig. 4

Histological evaluation of gastric tissues using H&E staining (magnification = 100×). A: Normal control group having an intact stomach. Black arrow indicates a normal morphology of the stomach with normal mucosal epithelial cells. Blue arrow indicates the normal sub-mucosal and muscular layer of the stomach; B: Ulcer control group without H. pylori. Black arrow indicates the extensive damage and loss of mucosal epithelial layer which is further extended to damage in the sub-mucosal layer. Blue arrow indicates the haemorrhages, inflammation and oedema of the sub-mucosal layer. C: Ulcer control group with H. pylori. Black arrow showed extensive damage and loss of mucosal epithelial layer. Blue arrow showed oedema, inflammation and haemorrhages in the sub-mucosal layer; D: Geraniol (15 mg/kg, b. i.d.). Black arrow showed moderate epithelial cell loss and haemorrhages. Blue arrow indicates the normal sub-mucosal layer; E: Geraniol (30 mg/kg, b. i.d.). Black arrow indicates a mild epithelial cell loss, oedema and neutrophil infiltration in mucosal layer. Blue arrow indicates the normal sub-mucosal layer; F: Standard Drugs (amoxicillin, 50 mg/kg; clarithromycin, 25 mg/kg and omeprazole, 20 mg/kg, b. i.d.). Black arrow indicates mild mucosal epithelial cell loss. Blue arrow showed the normal sub-mucosal layer.

Fig. 5

Histological evaluation of gastric tissues for H. pylori using Giemsa staining (magnification = 1000×). A: Ulcer control group with H. pylori. Black arrow showed extensive accumulation of H. pylori cells in between gastric mucosa and mucus layer; B: Geraniol (15 mg/kg, b. i.d.) treated rats. Black arrow showed the presence of moderate number of H. pylori cells in between gastric mucosa and mucus layer; C: Geraniol (30 mg/kg, b. i.d.) treated rats. Black arrow showed fewer H. pylori cells in between gastric mucosa and mucus layer; D: Standard Drug (amoxicillin, 50 mg/kg; clarithromycin, 25 mg/kg and omeprazole, 20 mg/kg, b. i.d.) treated rats. Absence of H. pylori cells in between gastric mucosa and mucus layer was observed.