Rhamnogalacturonan from Acmella oleracea (L.) R.K. Jansen: gastroprotective and ulcer healing properties in rats

Abstract

A rhamnogalacturonan (RGal) isolated from Acmella oleracea (L.) R.K. Jansen administered by oral route showed gastroprotective activity against acute lesions induced by ethanol. In this study, we investigated the gastric ulcer healing effect of RGal and its mechanisms of action. Intraperitoneal treatment of animals with RGal protected the gastric mucosa against acute lesions induced by ethanol, with participation of gastric mucus. Furthermore, in the chronic ulcer model, oral administration of RGal accelerates the gastric ulcer healing, accompanied by increasing of cellular proliferation and gastric mucus content, reducing inflammatory parameters and oxidative stress. In addition, the repeated 7 days-treatment of animals with RGal did not show alterations of clinical and behavioral symptoms, body and organs weights or plasmatic biochemical parameters. Collectively, these results showed that RGal has an interesting antiulcerogenic activity and could constitute an attractive molecule of interest for the development of new antiulcer agents.

Figure 1. Chemical structure of rhamnogalacturonan isolated from A. oleracea.

Figure 2. Effect of RGal on acute gastric lesions induced by ethanol P.A. in rats.

The animals were treated with vehicle (C: saline, 1 ml/kg, i.p.), omeprazole (Ome: 40 mg/kg, p.o.) or RGal (0.01, 0.1 e 1 mg/kg, i.p.) 30 min before oral administration of ethanol P.A. (0.5 ml/200 g). The results are expressed as mean±S.E.M. (n = 8). ANOVA followed by Bonferroni's test. *P<0.05 when compared to injured group (C).

Figure 3. Effect of RGal on chronic gastric ulcer induced by 80% acetic acid in rats.

The animals were orally treated with vehicle (C: water, 1 ml/kg), omeprazole (Ome: 40 mg/kg) or RGal (1, 3, 10 and 30 mg/kg) twice a day for seven days after the gastric ulcer induction. The results are expressed as mean±S.E.M. (n = 8). ANOVA followed by Bonferroni's test. *P<0.05 when compared to ulcerated group (C).

Figure 4. Representative macroscopic photograph of stomachs and histological hematoxylin/eosin (HE) sections (100×) of chronic gastric ulcer induced by 80% acetic acid in rats.

Animals were orally treated with vehicle (water, 1 ml/kg; Panel A and D), omeprazole (40 mg/kg; Panel B and E) or RGal (10 mg/kg; Panel C and F) twice a day for seven days after the gastric ulcer induction. Bars = 1 cm (A–C) and 2 mm (D–F), where M indicates margin of ulcer and B indicates base of ulcer.

Figure 5. Effect of RGal on the immunohistochemical staining for PCNA in chronic gastric ulcer induced by 80% acetic acid in rats.

Photomicrographs represent PCNA immunoreactivity of groups orally treated with vehicle (water, 1 ml/kg; Panels A and D), omeprazole (40 mg/kg; Panels B and E) or RGal (10 mg/kg; Panels C and F) twice a day for seven days after the gastric ulcer induction. Panels A-C: magnification = 7×, bars = 500 µm; Panels D-F: magnification = 100×, bars = 50 µm.

Figure 6. Effect of RGal on histochemical staining for mucin-like glycoproteins (PAS) in chronic gastric ulcer induced by 80% acetic acid in rats.

Representative images of groups orally treated with vehicle (water, 1 ml/kg; Panels A and D), omeprazole (40 mg/kg; Panels B and E) or RGal (10 mg/kg; Panels C and F) twice a day for seven days after the gastric ulcer induction. Panels A-C: magnification = 7×, bars = 500 µm; Panels D-F: magnification = 100×, bars = 50 µm.

Figure 7. Effects of RGal on MPO (Panel A) and TNF-α (Panel B) levels in chronic gastric ulcer induced by 80% acetic acid in rats.

The animals were orally treated with vehicle (C: water, 1 ml/kg), omeprazole (Ome: 40 mg/kg) or RGal (10 mg/kg) twice a day for seven days after the gastric ulcer induction. Naive (N): non-ulcerated group. The results are expressed as mean±S.E.M. (n = 8). ANOVA followed by Bonferroni's test. ^# P<0.05 when compared to naive (N). * P<0.05 when compared to ulcerated group (C).

Figure 8. Effect of RGal on the ability to scavenge the free-radical DPPH in vitro.

The figure shows the scavenging of DPPH radical by RGal (1, 10, 100 and 1000 µg/ml) or ascorbic acid (AA, 50 µg/ml) in vitro. The results are expressed as mean±S.E.M. (n = 8). ANOVA followed by Bonferroni's test. * P<0.05 when compared to control group (C).