Immunomodulatory Activities of Emerging Rare Ginsenosides F1, Rg5, Rk1, Rh1, and Rg2: From Molecular Mechanisms to Therapeutic Applications.

Ginsenosides, the primary bioactive components of Panax ginseng, have demonstrated significant immunomodulatory potential. While major ginsenosides have been extensively studied, rare ginsenosides produced through deglycosylation, heating, and steaming show enhanced biological activities with improved bioavailability. This review aimed to comprehensively analyze the immunomodulatory mechanisms, structure-activity relationships (SARs), therapeutic applications, and clinical translation strategies of five emerging rare ginsenosides: F1, Rg5, Rk1, Rh1, and Rg2. We conducted a comprehensive literature review examining the production methods, immunological effects, molecular mechanisms, pharmacokinetics, safety profiles, and clinical applications of these five compounds. Analysis focused on chemical structures, immune cell modulation, signaling pathways, disease model efficacy, and bioavailability enhancement strategies. Ginsenoside F1 uniquely demonstrated immunostimulatory effects, enhancing natural killer (NK) cell cytotoxicity and macrophage phagocytosis through mitogen-activated protein kinase (MAPK)/nuclear factor-κB (NF-κB) activation. Conversely, Rg5, Rk1, Rh1, and Rg2 exhibited anti-inflammatory properties via distinct mechanisms: Rg5 through Toll-like receptor 4 (TLR4)/NF-κB inhibition, Rk1 via triple pathway modulation (NF-κB, p38 MAPK, signal transducer and activator of transcription (STAT)), Rh1 by selective p38 MAPK and STAT1 inhibition, and Rg2 through modulation of both central nervous system (neuroinflammation) and peripheral organ systems. Structure-activity analysis revealed that sugar moiety positions critically determine immunological outcomes. Crucially, advanced delivery systems including nanostructured lipid carriers, self-microemulsifying systems, and specialized liposomes have overcome the major translational barrier of poor bioavailability, achieving up to 2.6-fold improvements and enabling clinical development. Safety assessments demonstrated favorable tolerability profiles across preclinical and clinical studies. These five rare ginsenosides represent promising immunomodulatory agents with distinct therapeutic applications. F1's unique immunostimulatory properties position it for cancer immunotherapy, while the complementary anti-inflammatory mechanisms of Rg5, Rk1, Rh1, and Rg2 offer opportunities for precision medicine in inflammatory diseases. Advanced formulation technologies and optimized production methods now enable their significant clinical translation potential, providing promising therapeutic options for immune-related disorders pending further development.