Furanocoumarin-rich extracts from Trichocline plicata as natural photosensitizers for the photodynamic inactivation of Leishmania amazonensis: Insights into ROS- and DNA-mediated mechanisms.

Cutaneous leishmaniasis (CL) is a neglected tropical disease with limited therapeutic options due to toxicity, resistance, and high costs. Photodynamic therapy offers a promising alternative; however, the systematic evaluation of furanocoumarin-rich plant extracts in Leishmania models remains limited. Despite the well-established photodynamic properties of individual furanocoumarins, no systematic evaluation of Trichocline plicata extracts has been performed in protozoan parasites. This study aimed to provide an integrated evaluation of the chemical composition, intrinsic photophysical properties, and biological photodynamic efficacy of furanocoumarin-rich extracts from Trichocline plicata against Leishmania amazonensis. Extracts from aerial and subterranean parts were chemically characterized by UHPLC-DAD and GC-MS, and their photodynamic potential was assessed through singlet oxygen and superoxide anion radical generation under UVA irradiation. Antiparasitic activity was tested in vitro, and morphological alterations were examined by optical and scanning electron microscopy, while cytotoxicity was evaluated in Vero cells. The dichloromethane extract from subterranean parts (DCM-SP.Ext.) showed the highest production of singlet oxygen and superoxide anion radical. Photodynamic treatment reduced parasite viability by up to 97%, comparable to amphotericin B, and microscopy revealed severe morphological damage in irradiated parasites. Mechanistic analyses using ROS quenchers and anoxic conditions demonstrated that both oxygen-dependent (Type I/II) and oxygen-independent (Type III) pathways contribute to parasite inactivation, supporting a multimodal photodynamic mechanism. DCM-SP.Ext. exhibited low toxicity in Vero cells, suggesting high selectivity toward the parasite. These findings establish T. plicata extracts, particularly DCM-SP.Ext., as efficient and selective natural photosensitizers capable of inducing multiple photodynamic mechanisms, supporting their potential as cost-effective plant-based agents for the photodynamic treatment of cutaneous leishmaniasis. This work highlights the potential of native plants as renewable sources of bioactive compounds for photodynamic applications in infectious diseases.