# Potential of Plant Stem Cells as Helpful Agents for Skin Disorders--A Narrative Review
## 4 Mechanistic Insights into the Skin Aging of Plant-Derived Stem Cells
### Antioxidant Activity  
Oxidative stress has long been considered one of the significant causes of premature aging [75]. The reactive molecule species, known as oxidants, cause damage to the structure and function of DNA, proteins, and lipids. Moreover, they have negative effects on particular regulatory systems and signaling pathways in cell metabolism [76]. Excessive accumulation of reactive oxygen species (ROS) can induce inflammation by triggering the signaling of the inflammatory process via nuclear factor kappa B (NF-xB) and secretion of the pro-inflammatory cytokines, e.g., interleukin 6 (IL-6) cellular senescence, which accelerates skin aging and may be the cause of several dermatoses [77; 78; 79; 55]. Moreover, ROS plays a major role in intrinsic skin aging, and this process is mostly dependent on transcription factors that activate and upregulate the MMP-1, MMP-3, and MMP-9 expression [76]. This way, fibroblasts reduce their proliferative activity, downregulate the extracellular matrix protein synthesis, and become senescent cells [79; 55]. The degradation of existing tissue, as well as a decline in the ability of keratinocytes to renew and differentiate, contributes to the aging process [76]. It has been postulated that plant-derived antioxidants, especially plant stem cells, may prevent cell damage by preserving stemness and reducing cellular senescence by ROS targeting [50; 80]. [PERSON] et al. observed that flavonoids and phenolic compounds in plant stem cell extracts exhibit antioxidant and anti-inflammatory properties by stimulating fibroblasts, increasing their proliferative capacity and migration, and inhibiting the NF-xB signaling pathway [55]. Several known plant-derived phenolic acids and vitamins with important antioxidant properties are listed in Table 3 below. However, [PERSON] et al. demonstrated that the genotypic effect of antioxidants depends on their dose and the type of target cells [45]. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Compound** & **Function as an Antioxidant** & **Ref** \\ \hline \multirow{6}{*}{Polyphenols, especially flavonoids and phenolic acids} & Protection against oxidative stress-induced cellular damage through & \\  & inhibition of reactive oxygen and nitrogen species (RONS) and the ability to & \\  & chelate transition metal ions such as Fe (II) and Cu (II), & \\  & Reduction in the expression of matrix metalloproteinases that catalyze the & \\  & degradation of skin proteins in epidermal keratinocytes and dermal fibroblasts & \\  & Protection of other antioxidants, such as vitamin C in the cytosol or vitamin E & \\  & in biological membranes & \\  & Protection against UV-induced peroxidation of cell membrane lipid acids, & \\  & reduction in oxidative stress caused by sunlight and oxygen & \\ \hline \multirow{6}{*}{Vitamin C} & ROS scavenger & \\  & Protection of the viability of cell membranes by promoting the expression of & \\  & genes encoding antioxidant enzymes & \\  & Inhibition of lipid peroxidation by regenerating fat-soluble vitamin E & \\  & Reduction in UVA-induced oxidative stress & \\ \hline \multirow{2}{*}{Vitamin E} & Inhibition of lipid peroxidation and formation of & \\  & 8-hydroxydeoxyguanosine—a biomarker of oxidative DNA damage & [16; 87] \\  & Protection against the damage of UVB-radiation & \\ \hline \multirow{6}{*}{Carotenoids} & Protection of cell membranes and lipoproteins from oxidative damage by & \\  & ROS scavengers & \\  & Regeneration oftocopherol from the tocopheroxyl radical & \\  & Prevention of photooxidative damage & \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Effect of topically applied major classes of phytoantioxidants on human skin. UV irradiation is one of the important factors in extrinsic skin aging. This process is caused by UV-A, UV-B, and infrared radiation. UV-B rays can cause DNA breaks in the epidermis and cause immunosuppressive and inflammatory effects [76]. Therefore, many cosmeceutical products promote UV protection activity.