**8. Conclusions**

A sedentary lifestyle and the consumption of high carbohydrate, proteins and fat have drastically changed the lives of humans, resulting in the production of ROS, which subsequently leads to oxidative stress. Moreover, these oxidative stresses are known to be linked with various diseases, and many attempts have been made to subside these with different medications. Although conventional therapies using antioxidants have been used in the past, they were mostly found ineffective in treating various diseases because of their incompetence in passing through the blood–brain barrier. To overcome these challenges, several antioxidant functionalized nanoparticles have been derived from biological sources, and evaluated by using scavenging assays under invitro conditions. Antioxidant properties of these nanocarriers make it a suitable candidate for targeted delivery, and can open new opportunities for combating oxidative stress in in vivo conditions. Furthermore, researchers are making continuous effort to slow down the toxic effects associated with the metallic and metalloid nanoparticles.

**Author Contributions:** Conceptualization, E.N., K.K., and D.K.; Manuscript writing, H.K. and K.B.; Manuscript editing, D.S.D., S.B., and R.V.; Critical revising, E.N., K.K., S.K.B. and D.K. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the University of Hradec Kralove (Faculty of Science VT2019-2021).

**Acknowledgments:** We acknowledge university of Hradec Kralove (Faculty of Science, VT2019-2021) for financial support.

**Conflicts of Interest:** The authors declare no conflict of interest.
