Phytochemical Constituents and Biological Activities of Ononis spinosa: A Comprehensive Review

Ononis spinosa L. (Fabaceae), commonly known as spiny restharrow, is a widely distributed medicinal plant traditionally used in European and Middle Eastern phytotherapy, particularly for the management of urological and inflammatory conditions. Despite its long-standing ethnomedicinal relevance, comprehensive syntheses of its phytochemical profile and biological activities remain limited. This review aimed to summarize current evidence regarding the chemical constituents and pharmacological effects of O. spinosa. Four electronic databases (PubMed, Scopus, Web of Science, and SpringerLink) were searched for studies published between 1997 and 2024. The search yielded 308 records; after duplicate removal and eligibility screening, 34 studies met the inclusion criteria. The phytochemical profile of O. spinosa is characterized predominantly by isoflavonoids (e.g., ononin and other formononetin derivatives), triterpenes, phenolic acids, and additional polyphenolic compounds. Although the phytochemical profile of O. spinosa includes multiple classes of secondary metabolites, this review places particular emphasis on phenolic compounds, given their prevalence and well-documented biological activities. Experimental evidence indicates a broad spectrum of biological activities, including anti-inflammatory effects (associated with cPLA2α inhibition and cytokine modulation), antibacterial and antifungal activity, antioxidant capacity, wound-healing and dermatological benefits, as well as diuretic and anti-adhesive effects in urinary models. Additional reported properties include antiproliferative, anti-adipogenic, analgesic, and neurotrophic activities. Proposed mechanisms of action involve enzyme inhibition (e.g., Hyal-1 and COX-2), modulation of transient receptor potential (TRP) channels, redox regulation, and interference with microbial adhesion and inflammatory signaling pathways. Overall, O. spinosa contains bioactive compounds exhibiting a wide range of pharmacological activities supported by in vitro and in vivo studies. Among the investigated effects, anti-inflammatory, urological, and wound-healing activities appear to be the most promising targets for future research. These findings highlight its therapeutic potential while emphasizing the need for well-designed clinical studies to further validate its medicinal applications.