**3. Antioxidants combat oxidative stress**

While broad-spectrum sunscreens which absorb and reflect harmful solar radiation remain the most effective protection against immediate solar UV damage (which result in CPD formation), antioxidants are crucial in combating oxidative stress caused by ROS. Skin's antioxidant system consists of vitamins (vitamins C and E), enzymes (catalase and superoxide dismutase), glutathione, and coenzyme Q10 (CoQ10). As these antioxidants perform their protective actions and are degraded by ROS, they are reactivated by other

prone to the damaging effect of free radicals (Sen, et al., 2010). Prolonged oxidative stress to the lipid bilayer can lead to membrane rupture and apoptosis. Lipid peroxidation is, in fact, used as a marker of oxidative stress since the lipid membrane is easily attacked by free

Cellular DNA damage caused by UV radiation may be classified into two components. The first is that caused by an immediate photochemical reaction (direct) while the other is caused by the formation of ROS (indirect). Direct damage (through direct UV absorption) results primarily in the DNA product cyclobutane-pyrimidine dimer (CPD) (Farage, et al., 2010). On the other hand, indirect damage (through ROS formation) causes DNA mutation due to a replication error induced by modified guanine base (8-oxo-guanine). Direct UV absorption also leads to the formation of 8-oxo-guanine (8oGua) as well as the photoproduct

The negative effect of free radicals may be mitigated by antioxidants primarily through their radical-scavenging ability. These antioxidants stabilize radicals by donating electrons and thus preventing oxidation of DNA or other cellular components. While the body is equipped with its own defense system against reactive oxygen species (ROS) and other free radicals produced in the body, it also relies on external (exogenous) antioxidants including those contained in food. As environmental conditions lead to premature aging, a search for

Free radicals cause damage in the body because of their instability and high reactivity. ROS are of particular interest. During aerobic respiration, mitochondrial electron transport results in the formation of a ROS (superoxide) as a by-product. Solar UV radiation also leads to formation of ROS. Oxygen is particularly vulnerable to radical formation due to its electronic configuration with two valence shell unpaired electrons. Thus, there are several types of ROS including superoxide, hydrogen peroxide, nitric oxide, and hydroxyl radical. Free radicals of other atomic species specifically nitrogen are also formed within the body. ROS can potentially react with other cellular entities including DNA which can lead to DNA modification and ultimately bodily harm. The guanine base in DNA is particularly susceptible to attack by ROS formed by solar UV radiation. Oxidation reactions which

modify the guanine base may also lead to single-strand breaks in DNA (Held, 2010).

including intracellular and intercellular communication (Held, 2010).

**3. Antioxidants combat oxidative stress** 

While the effects of oxidative stress on the body vary according to type and duration, cells often halt division (enter G0 phase) and may even undergo apoptosis under severe stress. The general response to oxidative stress is cell cycle arrest through the expression of various inhibitor proteins (such as p21). Nevertheless, ROS also serve useful roles within the body

While broad-spectrum sunscreens which absorb and reflect harmful solar radiation remain the most effective protection against immediate solar UV damage (which result in CPD formation), antioxidants are crucial in combating oxidative stress caused by ROS. Skin's antioxidant system consists of vitamins (vitamins C and E), enzymes (catalase and superoxide dismutase), glutathione, and coenzyme Q10 (CoQ10). As these antioxidants perform their protective actions and are degraded by ROS, they are reactivated by other

pyrimidine (6-4) pyrimidinone although in proportionally lower amounts.

radicals.

**2. Free radicals & ROS** 

a suitable antioxidant product is vital.

antioxidants. Because several types of ROS may be formed through environmental insult, several types of antioxidants are produced in the skin. Thus antioxidants come in various forms (vitamins, enzymes, etc.) and may be either lipophilic or hydrophilic to function in a variety of areas.
