Biological Activities and Valuable Bioactive Compounds from Portuguese Medicinal Plants

Currently, there are more than 85,000 plant species that have been documented for medical use globally. This implies, plant derived natural products hold great promise for discovery and development of new pharmaceuticals in diverse human ailments. The lack of effective pharmaceutical formulas and the resistance created by current antibiotic pathogens, as well as oxidative stress new therapeutic agents from plants. In fact, several studies have shown that medicinal plants possess antioxidant properties due largely to their phytochemical profile. Endemic plants can be a source of new bioactive compounds able to prevent several diseases such as cancer, diabetes, hypertension, and Alzheimer’s disease by combating oxidative stress and its associated pathologies. The purpose of this study was to evaluate the contents of total phenolics, flavonoids, and caffeine in six medicinal plants used traditionally in phytotherapy, usually consumed as tea or infusion namely: Camellia sinensis, Melissa officinalis, Lippia citriodora, Cymbopogon citratus, Matricaria chamomilla, and Tilia cordata. Significant variations in total phenolics and flavonoids content were found among analyzed plants and depending on the nature of the extract. The concentration of caffeine was also very dissimilar and followed the sequence M. officinalis < T. cordata < C. citratus < M. chamomilla < L. citriodora < C. sinensis. Also, the antioxidant activity of each plant was found to vary according to C. citratus (90.9%) > C. sinensis (87.8%) > M. officinalis (50.7%) > M. chamomilla (45.3%) > T. cordata (32.2%) > L. citriodora (28.0%).