An Updated Review on the Botany, Ethnopharmacology, Phytochemistry, Biological Activities, Quality Control, and Applications of Lycopodium japonicum Thunb.

Lycopodium japonicum Thunb. (L. japonicum) is a traditional medicinal herb that functions to dispel wind-dampness, relax the tendons, and unblock the collaterals (qu feng chu shi and shu jin huo luo, typical TCM syndrome-oriented therapeutic concepts). Clinically, it is frequently prescribed for the management of arthralgia, rheumatic conditions, and orthopedic ailments. Up to now, a total of 177 chemical constituents have been isolated and structurally elucidated from L. japonicum. Among these, alkaloids and triterpenoids are considered principal bioactive constituents, which exert multiple pharmacological effects including antitumor, anti-inflammatory and acetylcholinesterase-inhibitory effects. Nevertheless, their contributions to the overall pharmacological activities still require further mechanistic validation. Recently, the spores of L. japonicum have emerged as a promising natural platform for targeted drug delivery. In parallel, analytical strategies for its quality control have evolved from single-marker quantification toward simultaneous multi-component determination. Nevertheless, several key issues, including the standardization of formulation protocols, mechanistic clarification of pharmacological actions, and robust quality control systems, still require systematic investigation and refinement. As a traditional herbal medicine, it has relatively limited data regarding its in vivo absorption, toxicology, pharmacokinetics, and clinical trials. This review systematically summarizes the research advances of L. japonicum in phytochemistry, pharmacological activities, and quality control. It also proposes evidence-based recommendations for addressing key issues in current research, including unclear chemical composition, poorly understood pharmacological mechanisms, and the absence of quality standards. This review aims to provide an updated reference for future phytochemical, pharmacological, toxicological, and quality-control research on L. japonicum.