Molecular mechanisms of skin photoaging and plant inhibitors

Abstract

Skin ageing is a complex multifactorial process occurring in all living beings. It generally comprises two independent and distinct processes, i.e., intrinsic, age-dependent or chronological aging and premature aging, or photoaging which is the result of undue exposure of the skin to ultraviolet (UV) radiations. Photoaging can be prevented or the effects of photoaging can be reduced by the use of certain anti-aging and anti-wrinkle agents. The extracellular matrix (ECM) which forms the outermost part of skin comprises fibroblasts and proteins such as collagen and elastin. Degradation of ECM is directly linked to skin aging and is responsible for the increase in activity of certain enzymes such as collagenase, elastase, and hyaluronidase (HYAL) that are involved in skin aging. With aging there is decrease in the levels of elastin, collagen, and hyaluronic acid which leads to loss of strength and flexibility of skin and appear as wrinkles on the skin. Further, the increase in the activity of collagenase, elastase, and HYAL is triggered by the high levels of reactive oxygen species produced when the skin is exposed to excessive UV radiations leading to skin aging. Today, in the age of modern science and advanced technology, although many techniques such as laser rejuvenation, plastic surgery, and lots of synthetic products such as sunscreen lotions, creams are available yet, there is a place for natural, herbal anti-aging cosmetics. Various botanical extracts have the power to reduce the appearance of skin aging and enhance the beauty of the skin. Medicinal plants have several phytoconstituents such as polyphenols, alkaloids, tannins, saponins, carotenoids, and terpenoids which possess antioxidant properties and can be used in treating the signs of aging. Some plants contain phenolic compounds which have free-radical scavenging property and can suppress aging. Some plants or their extracts possess several other constituents that may have the capability of inhibiting various enzyme such as HYAL, elastase, and matrix metalloproteinases enzyme that play a major role in skin aging. Some of them may possess the free radical scavenging or antioxidant property to fight against the signs of aging. This review focuses on the compilation of medicinal plants and natural compounds as anti-aging and anti-wrinkling agents along with their chemical constituents based on their possible molecular mechanism of action. The present review will facilitate the scientists working in this area for the development of new anti-aging and anti-wrinkle formulations with better efficiency and safety.