Plants against Helicobacter pylori to combat resistance: An ethnopharmacological review

Graphical abstract

polysaccharides, which responsible for antimicrobial activity (Fig. 2) are discussed within this review in Table 2.

Sterol
The presence of a free OH group in C-3 is necessary for the antiulcer action of triterpenoids and sterols consistently, the only structural difference between the active 3a-hydroxymasticadienonic acid (Fig. 3, 1) and the inactive masticadienonic acid (Fig. 3, 2) is the presence of an OH group and a C¼O group in the C-3 [14,15].
The structure activity relationship shows that the presence of OCH 3 group in the C-5 or C-7 positions, the double bonds at C-2 and C-3 and the presence pof an intact C-ring appear to increase gastroprotection potential. On the other hand, substitution with OH or OCH 3 groups at C-3, C-6, or C-8 diminish the gastroprotective action.

Zingiber officinalis
Root extract 6-gingesulphonic acid Inhibit thromboxane synthetase [45,197,198,199,200,201,202]   According to Lee et al. [33], the saponins display antisecretory action by inhibiting acid secretion, total acid output, and lowering the pH of gastric juice [34].

Terpenes
Nerolidol (Fig. 6) has an antiulcerogenic and cytoprotective effect by increasing mucus production via increasing the PG, improving the gastric blood flow, and increasing the secretion of gastric bicarbonate and mucus [35]. In addition, terpenoids act as antioxidants, reduce the lipid peroxidation levels, and increase the activity of antioxidant enzymes in the gastric mucosa [36,37]. Menthol is a monoterpene that increases the maintenance of SH compounds and the amount of mucus and PG production. It also possesses an antisecretory effect, in addition to antioxidant, antiinflammatory, and antiapoptotic actions [38,39]. Oleanolic acid is a triterpene that improves healing in the ulcer model. The low toxicity and the widespread occurrence in various plants support the potential development of new antiulcer drug based on triterpenes or their derivatives [37].

Polysaccharides
Arabinogalactan (Fig. 7) has the ability to bind on the gastric mucosa acting as a protective layer, in addition to its antisecretory activity towards gastric juice. The mucosal protective activity of Arabinogalactan is provided by an increased mucus synthesis and free radical scavenging activity. The particular mechanisms of polysaccharides are described by their potential to bind on the surface of the gastrointestinal mucosa, thereby acting as a protective layer, in addition to their antisecretory action. Their mucosal protective potentials are provided by an increased mucus

Conclusion
H. pylori inhibition with antibiotic therapies has a limitation mainly owing to antibiotic resistance. Medicinal herbs provide another opportunity to inhibit H. pylori. Medicinal herbs might also provide successful approach to decrease stomach cancer. However, potential cytotoxicity and side effects might present from those herbs. Therefore, further cytotoxicity investigation will be required.

Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.