Abstract
The skin, as the largest external organ, is exposed to many environmental factors, such as sunlight and pollution, as well as some synthetic ingredients in cosmetic products used in excess by most people of all ages throughout their lives. Under the influence of these factors and with age, the amount of the key building protein, collagen type I, decreases, which leads to a deterioration in the appearance and condition of the skin. Currently, when the average life expectancy increases, the esthetic aspect and maintaining healthy skin are particularly important. In the cosmetic and pharmaceutical industries, attempts have long been made to prevent skin aging by the application of products containing natural compounds, mainly due to their high antioxidant activity. This review collects natural compounds, mainly polyphenols, with stimulating and protective effects on collagen type I in human skin fibroblasts, along with a description of the mechanisms of their action. Some of them have been tested on mice and rats, as well as in clinical trials, and in most cases, the results have been very promising. Nevertheless, there is still a need for an intensification of clinical studies in order to determine their appropriate dosage, safety, and effectiveness.