A comprehensive review of Helminthostachys zeylanica (L.) Hook.: medicinal uses, distribution, conservation, population genetics and phylogeography

Helminthostachys zeylanica (L.) Hook. is a unique fern with a rich ethnomedicinal history and a broad but patchy distribution across tropical Asia and the Pacific regions. This review compiles current knowledge on its taxonomy, morphology, medicinal uses, bioactive compounds, and potential pharmacological activities. We also emphasize its cultural importance and the wide range of conditions it is used to treat across different regions, including respiratory and hepatic disorders, snakebites, and reproductive health issues. Phytochemical studies have characterized a distinctive series of prenylated flavonoids (ugonins) and other compounds; extracts and isolated compounds show antioxidant, anti-inflammatory, hepatoprotective, anticancer and other activities, almost entirely in preclinical models. Despite its wide range, H. zeylanica populations are in decline due to habitat loss and overharvesting, and it is considered rare or endangered in several countries. We review its current distribution and conservation status by country and discuss threats such as over-collection and poor natural regeneration. Recent insights and methodologies in population genetics and phylogeography are considered, emphasizing the need for genetic data to inform conservation. Because no population-genetic data yet exist for the species, we outline research and conservation priorities, including range-wide genetic sampling, to guide future conservation of this ancient medicinal fern. Our review uniquely integrates ethnomedicinal knowledge, pharmacological evidence, conservation biology, and population genetic/phylogeographic perspectives to support sustainable use and evidence-based conservation planning for H. zeylanica . However, the available evidence remains largely preclinical, and significant gaps persist in extract standardization, safety evaluation, and population-level genetic data needed for conservation management.