Unveiling Pulmonaria rubra Schott: Phytochemical Characterisation and Evaluation of Its Neuroprotective Potential

Pulmonaria rubra (Boraginaceae) is a widely distributed plant in Bulgaria, yet its phytochemical profile and therapeutic potential have remained unexplored. P. rubra methanol extract (PRE) was evaluated through phytochemical profiling and in vitro neuroprotective and antioxidant assays. Rat brain synaptosomes, mitochondria and microsomes were treated with PRE alone, and in combination with 6-hydroxydopamine and tert-butyl hydroperoxide as toxic agents. The extract exhibited concentration-dependent protective effects in all subcellular models. Additionally, it was tested on hMAOA/B and different isoforms of CYP450 enzymes, but it did not show any activity in the tested conditions. In the UHPLC-HRESIMS analysis, 26 secondary metabolites were identified, mainly hydroxycinnamic acids and caffeoyl oligomers, flavonoids, a lignan (globoidnan A), and the terpenoid glycoside roseoside. Seven compounds were identified via UHPLC-UV method using reference compounds: rosmarinic acid, rutin, quercetin-3-O-glucoside, astragalin, apigenin-7-O-glucoside, apigenin-7-O-glucuronide and alcesefoliside, with the latter two being reported for the first time in genus Pulmonaria. The quantity of rosmarinic acid in PRE was 4.35%, distinguishing the compound as the main bioactive molecule in the species. Characterized by its high content of rosmarinic acid, P. rubra represents a highly viable candidate for subsequent development into standardized phytopharmaceuticals targeting oxidative stress-related neurodegenerative diseases.