Targeting Inflammation with Natural Products: A Mechanistic Review of Iridoids from Bulgarian Medicinal Plants

Chronic, low-grade inflammation is a key contributor to the development of numerous non-communicable diseases (NCDs), including cardiovascular, metabolic, and neurodegenerative disorders. Conventional anti-inflammatory drugs, such as nonsteroidal anti-inflammatory drugs (NSAIDs) and corticosteroids, often present safety concerns with prolonged use, highlighting the need for safer, multi-targeted therapeutic options. Iridoids, a class of monoterpenoid compounds abundant in several medicinal plants, have emerged as promising bioactive agents with diverse pharmacological properties. They exert anti-inflammatory and metabolic regulatory effects by modulating key signaling pathways, including nuclear factor kappa B (NF-κB), mitogen-activated protein kinase (MAPK), Janus kinase/signal transducer and activator of transcription (JAK/STAT), adenosine monophosphate-activated protein kinase (AMPK), and peroxisome proliferator-activated receptor (PPAR) pathways. This review provides a comprehensive summary of the major iridoid metabolites derived from ten Bulgarian medicinal plant species, along with mechanistic insights from in vitro and in vivo studies. Documented biological activities include anti-inflammatory, antioxidant, immunomodulatory, antifibrotic, organoprotective, antibacterial, antiviral, analgesic, and metabolic effects. By exploring their phytochemical profiles and pharmacodynamics, we underscore the therapeutic potential of iridoid-rich Bulgarian flora in managing inflammation-related and metabolic diseases. These findings support the relevance of iridoids as complementary or alternative agents to conventional therapies and highlight the need for further translational and clinical research.