Catalpol: an natural multifunctional iridoid glycoside with promising therapeutic properties

Catalpol, an iridoid glycoside predominantly derived from the fresh or dried root tuber of Rehmannia glutinosa Libosch (a member of the Scrophulariaceae family), it is a representative compound with the highest content in Rehmannia glutinosa Libosch, and it is also a key index component for evaluating the quality of Rehmannia glutinosa Libosch. Since 2005, it has been continuously included in various editions of China Pharmacopoeia. In this review, we collected relevant data from the Web of Science, PubMed, China National Intellectual Property Administration and China Knowledge Resource Integrated databases in recent 5 years. Catalpol exhibits a broad range of therapeutic effects, addressing various diseases through intricate mechanisms. These include organ- and tissue-protective actions on the kidneys, bones, nervous system, heart, brain, liver, lungs, uterus, ovaries, and more, alongside notable anti-arthritis, anti-cancer, and anti-diabetic properties. The protective mechanisms of catalpol primarily involve its anti-inflammatory, antioxidative stress, anti- or pro-apoptotic, anti-fibrotic, metabolism-regulatory, anti-endoplasmic reticulum stress (ERS), and pyroptosis-modulating functions. Furthermore, catalpol influences a variety of signaling pathways, cells, and molecules, and through these multifaceted actions, it achieves its maximal therapeutic potential. In recent years, the development of different targeted drug delivery formulations and administration routes of catalpol maximise its efficacy has become a major focus of research. What's more worth mentioning is that "catalpol tablets", a new class I Chinese medicine developed on the basis of this monomer component, has been approved to enter the clinical trial stage in China. However, in-depth investigation is required to elucidate the mechanisms of action of catalpol, and more clinical trials are required to assess the clinical value of this compound.