Glycyrrhizic acid, a major active component of licorice root (Glycyrrhiza glabra), has been investigated for its potential in supporting or treating duodenal ulcers. Scientific interest is based on its anti-inflammatory, mucoprotective, and anti-ulcer properties observed in both experimental and some clinical contexts. Studies suggest that glycyrrhizic acid and its aglycone, glycyrrhetinic acid, can enhance mucosal defense mechanisms by increasing the production of mucus and reducing gastric acid secretion. Additionally, these compounds exhibit anti-Helicobacter pylori activity, which is relevant since this bacterium is implicated in the pathogenesis of duodenal ulcers.

Clinical evidence, while modest, includes some randomized controlled trials and observational studies, particularly from Japan and other Asian countries, using deglycyrrhizinated licorice (DGL) or preparations containing glycyrrhizic acid. These studies have reported symptom relief and improved healing rates compared to placebo, though the sample sizes are typically small and methodologies variable. Notably, DGL is more commonly used in Western herbal practice to avoid glycyrrhizic acid's mineralocorticoid side effects (e.g., hypertension, hypokalemia), but some studies do involve glycyrrhizic acid-containing licorice extracts.

Overall, while traditional use has long supported licorice in gastrointestinal complaints, there is moderate scientific validation specifically for glycyrrhizic acid in duodenal ulcer management. However, the quality and quantity of evidence are not robust enough for a high confidence rating, and safety concerns limit its long-term use.