Onosma L. as a source of anticancer agents: phytochemistry to mechanistic insight

Onosma (O.) is a genus of perennial flowering plants in the family Boraginaceae with approximately 250 species widely dispersed in temperate, tropical, and subtropical areas. It is traditionally used to treat rheumatism, fever, asthma, stomach irritation, and inflammatory ailments. The bioactive constituents present in the genus O. include benzoquinones, naphthazarins, alkaloids, phenolic, naphthoquinones, and flavonoids whereas shikonins and onosmins are the most significant. The review compiled contemporary research on O. L., including its distribution, morphology, traditional applications, phytochemistry, ethnopharmacology, and toxicology. This review also highlights a few critical challenges and possible future directions for O. L. research. Modern research has demonstrated a wide range of pharmacological effects of different species of O. L., including anti-diabetic, anticancer, anti-inflammatory, and cardiovascular protective. However, the studies on the O. genus are still not fully explored, therefore, researchers need to discover novel products with their toxicity studies, molecular mechanism, and associated side effects. Future exploration of potent constituents from this genus and clinical trials are required to explore its pharmacological importance.