Diffractaic acid (CAS No.436-32-8 ), a secondary metabolite derived from the lichen Pseudocyphellaria magellanica, demonstrates notable biological activities, including cytotoxic effects against various human cancer cell lines (HCT116, HeLa, and MCF-7) with IC?? values ranging from 42.2 to 93.4 μM, and inhibitory activity against Mycobacterium tuberculosis (MIC of 41.7 μM). In vivo studies in rats show that diffractaic acid (25–200 mg/kg) can attenuate indomethacin-induced gastric mucosal injury by reducing neutrophil infiltration, lipid peroxidation, myeloperoxidase activity, and gastric lesions, while restoring antioxidant enzyme activities (SOD and GPx). Additionally, diffractaic acid exhibits analgesic effects by decreasing acetic acid-induced writhing and increasing the pressure pain threshold in animal models.

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