5. Conclusions

One of the paradoxes of life on Earth is that, on the one hand, oxygen is necessary for the life of aerobic organisms. On the other hand, increased concentrations of oxygen and especially its reactive metabolites (reactive oxygen species) may lead to the development of numerous diseases. A major source of free radicals in biological systems is molecular oxygen (O2). The results of our in vitro assays of examined five different extracts of Laurus nobilis leaves expressed significant protective effects on ROS (DPPH, O2 •, NO, and OH radicals), which was found to be correlated to different compounds. HPLC-DAD analysis indicates a significant presence of flavonoids and phenolic in the EtOAc and n-BuOH extracts. Quercetin glycosides and flavonoids (e.g., kaempferol-3-O-Glc) were detected in EtOAc extract. In addition, the presence of phenolic acids (such as caffeic acid) and flavonoids (rutin and kaempferol) was proven in the H2O extract. The amount of flavonoids in extracts plays a significant role in their antioxidant capacity, and it can be concluded that ethyl acetate proved to be the best solvent for extraction of plant material. Furthermore, it can be concluded that these extracts can be used in the preparation of various herbal medicines.
