Protective, Anti-Inflammatory, and Anti-Aging Effects of Soy Isoflavones on Skin Cells: An Overview of In Vitro and In Vivo Studies

Isoflavones are found in numerous plant species within the Leguminosae family; however, soy isoflavones are particularly significant in practice and have been extensively studied in recent years. The health-promoting potential of orally administered soy isoflavones is widely documented in the scientific literature, and many review articles have been developed to highlight their significance. However, it should be noted that soy-isoflavone-rich extracts and isolated soy isoflavones, such as genistein and daidzein, are also often applied topically as ingredients in many formulations, including face creams, tonics, and emulsions. New delivery systems are continuously being developed to enhance the skin permeability of isoflavones, thus improving their efficacy. In this context, their direct activity on skin cells is an important aspect of scientific research. The anti-inflammatory, protective, and antioxidant properties of isoflavones and soy extracts make them promising cosmetic ingredients with anti-aging potential because inflammation and the accumulation of reactive oxygen species (ROS) can lead to structural and functional changes in skin cells, accelerating the aging process. This review provides an overview of research on the impact of the application of soy isoflavone extract and soy-derived isoflavones on skin cells, with a focus on the documented molecular mechanisms underlying their effects. This study aims to offer essential insights to aid in the development of functional cosmetics and future clinical applications.