Combining in vitro and in silico approaches to evaluate the multifunctional profile of rosmarinic acid from Blechnum brasiliense on targets related to neurodegeneration.

Natural products are important sources of chemical diversity leading to unique scaffolds that can be exploited in the discovery of new drug candidates or chemical probes. In this context, chemical and biological investigation of ferns and lycophytes occurring in Brazil is an approach adopted by our research group aiming at discovering bioactive molecules acting on neurodegeneration targets. In the present study, rosmarinic acid (RA) isolated from Blechnum brasiliense showed an in vitro multifunctional profile characterized by antioxidant effects, and monoamine oxidases (MAO-A and MAO-B) and catechol-O-methyl transferase (COMT) inhibition. RA showed antioxidant effects against hydroxyl (HO(•)) and nitric oxide (NO) radicals (IC50 of 29.4 and 140 μM, respectively), and inhibition of lipid peroxidation (IC50 of 19.6 μM). In addition, RA inhibited MAO-A, MAO-B and COMT enzymes with IC50 values of 50.1, 184.6 and 26.7 μM, respectively. The MAO-A modulation showed a non-time-dependent profile, suggesting a reversible mechanism of inhibition. Structural insights on RA interactions with MAO-A and COMT were investigated by molecular docking. Finally, RA (up to 5 mM) demonstrated no cytotoxicity on polymorphonuclear rat cells. Taken together, our results suggest that RA may be exploited as a template for the development of new antioxidant molecules possessing additional MAO and COMT inhibition effects to be further investigated on in vitro and in vivo models of neurodegenerative diseases.