Alkaloids Mediate Multi-Level Modulation of Gastric Carcinogenesis: From Antibacterial and Anti-Inflammatory Actions to Antitumor Effects

Gastric cancer is one of the malignancies with the highest incidence and mortality worldwide. Helicobacter pylori (H. pylori) infection is the primary driving factor in its development. The progression of gastric mucosal malignancy follows the Correa cascade model: “chronic non-atrophic gastritis → chronic atrophic gastritis (CAG) → intestinal metaplasia (IM) → dysplasia (Dys) → gastric cancer.” Currently, clinical management faces major challenges, including increasing antibiotic resistance in H. pylori, limited pharmacological options for gastric precancerous lesions, and treatment resistance and toxicity in established gastric cancer. This review synthesizes current evidence on BBR, COP, EPI, PAL, and JAT and organizes their reported actions into a three-tier intervention framework. At the first tier, etiologic and inflammatory interception, individual alkaloids suppress H. pylori persistence through direct antibacterial injury, urease inhibition, and modulation of bacterial virulence and antibiotic susceptibility, while attenuating infection-driven inflammatory and immune responses. At the second tier, modulation of precancerous mucosal progression, preclinical studies indicate that these compounds can ameliorate gastric glandular injury and may attenuate biological processes associated with progression toward intestinal metaplasia and dysplasia. At the third tier, antitumor and adjunctive intervention in established gastric cancer, alkaloids inhibit proliferation, induce cell-cycle arrest and apoptosis, suppress invasion and metastasis, and regulate non-coding RNA and epigenetic networks; BBR-centered preclinical studies further suggest potential chemosensitizing and supportive effects. This review integrates the five alkaloids BBR, COP, EPI, PAL, and JAT and systematically elucidates their mechanisms of action across the pathological continuum from H. pylori infection and chronic inflammation to precancerous lesions and ultimately gastric cancer. It establishes a stage-oriented, compound-specific analytical framework to clarify the pharmacological positioning of these compounds, identify priorities requiring further validation, and guide future mechanistic and translational research.