The skin, the largest human organ, is constantly exposing to the external environment. Exposure to a variety of environmental stress factors, particularly ultraviolet (UV) radiation in sunlight; can damage the skin. Sunlight can break down into three types of nonionizing electromagnetic radiation infrared (IR) (780–3000 nm); visible (400–780 nm), and UV (100–400 nm).
The percentages of energy radiated to the Earth, in the total energy emitted by the Sun, are 53% IR; 39% visible, and 8% UV. On the basis of its physiological and biological effects; UV radiation can be further divided into three main bands—the 315–400 nm band (designated as UV-A), the 280–315 nm band (designated as UV-B), and the 100–280 nm band (designated as UV-C).
Ozone layer and the atmosphere
The solar UV radiation is drastically as it passes through the ozone layer and the atmosphere; as a result, the proportion of UV rays in the sunlight reaching the Earth’s surface of 95% UV-A and 5% UV-B. Although it comprises only a small portion of the total UV radiation, UV-B is thought to be more harmful than UV-A, since UV-B is most active in damaging the skin and eyes.
UV-A and UV-B are also to genotoxic, meaning they can induce photochemical damage in cellular DNA and proteins. Consequently, exposure to UV-A and UV-B; stimulates skin photoaging and can responsible for the induction of skin cancer. Skin photoaging is by the development of pigmentary disorders, such as solar lentigines, fine and coarse wrinkles, and benign, premalignant; malignant skin tumors on sun-exposed skin.
Prolonged exposure to ultraviolet (UV) radiation causes photoaging of the skin and induces a number of disorders; including sunburn, fine and coarse wrinkles, and skin cancer risk. Therefore, the application of sunscreen has gained much attention to reduce the harmful effects of UV irradiation on our skin. Recently, there has a growing demand for the replacement of chemical sunscreens with natural UV-absorbing compounds.
Mycosporine-like amino acids
Mycosporine-like amino acids (MAAs), promising alternative natural UV-absorbing compounds; are a group of widely low molecular-weight, water-soluble molecules that can absorb UV radiation and disperse the absorbed energy as heat; without generating reactive oxygen species (ROS). More than 30 MAAs have characterized, from a variety of organisms.
In addition to their UV-absorbing properties, there is substantial evidence that MAAs have the potential to protect against skin aging, including antioxidative activity, anti-inflammatory activity, inhibition of protein-glycation, and inhibition of collagenase activity.
This review will provide an overview of MAAs; as potential anti-aging ingredients, beginning with their structure, before moving on to discuss the most recent experimental observations; including the molecular and cellular mechanisms through which MAAs might protect the skin. In particular, we focus on the potential anti-aging activity of mycosporine-2-glycine (M2G).