Investigação da atividade antioxidante in vitro e da composição química de diferentes extratos de plantas medicinais

Abstract

Oxidative stress (OS) is involved in the development of several disorders involving the central nervous system, such as Alzheimer s disease (AD). Considering the limitations of current therapeutics for AD, there is still a great demand for discovery of new medical alternatives. In the first part of the present study it was investigated the antioxidant capacity and the chemical composition of three plants popularly used to treat neurological disorders: Melissa officinalis, Matricaria recutita and Cymbopogon citratus. The antioxidant effect of some phenolic compounds was also examined for comparative purposes. All plant extracts were effective in to combat OS, but Melissa officinalis presented the highest antioxidant effect. Among the purified compounds, quercetin had the highest antioxidant activity followed by gallic acid, quercitrin and rutin. In this work, we have demonstrated that the plant extracts could protect against OS induced by various pro-oxidant agents that induce lipid peroxidation by different process. Based on this study, which indicates that Melissa officinalis could be an effective agent in the prevention of various neurological diseases associated with OS. In the second part of this study, it was investigated the chemical composition and antioxidant activity of different fractions from Melissa officinalis extract. Furthermore, it was verified the effect of the most antioxidant fraction on acethylcholinesterase (AChE) activity and the effect of gallic acid on the matrix metalloproteinase-2 (MMP-2) activity. Ethyl acetate fraction presented the highest flavonoids content as well as antioxidant activity when compared with other tested fractions and also it caused AChE inhibition. Moreover, gallic acid inhibited MMP-2 activity. In conclusion, M. officinalis ethyl acetate fraction is suggested to be further investigated for its possible use in the treatment of AD, due its antioxidant, anticholinesterase activities and the MMP-2 inhibitory capacity of their phenolic compound, gallic acid.