Photoprotective

Photoprotective is an adjective describing processes, substances, or strategies that reduce damage or adverse effects caused by exposure to light, especially ultraviolet radiation. In biology, photoprotection refers to mechanisms that limit light-induced damage to photosynthetic organisms or guard against excess light in tissues. Plants and algae employ non-photochemical quenching, which dissipates excess excitation energy as heat, and regulate pigment composition via the xanthophyll cycle (violaxanthin, antheraxanthin, zeaxanthin). Protective pigments such as carotenoids and flavonoids absorb or quench reactive oxygen species, while repair cycles replace damaged proteins in photosystems, notably the D1 protein of photosystem II, maintaining photosynthetic efficiency.

In dermatology and consumer products, photoprotective often describes agents that shield skin or materials from UV damage. Sunscreens use organic UV filters and inorganic UV absorbers to absorb or reflect UV-A and UV-B radiation, reducing DNA damage and photoaging. Antioxidants and vitamins may augment protection by neutralizing reactive species, and physical barriers such as clothing or coatings add photoprotective effects.

In materials science, photoprotective approaches prevent photo-degradation of polymers and paints. UV absorbers, hindered amine light stabilizers, and radical scavengers are incorporated into formulations to slow chain scission, color loss, and loss of mechanical properties under sunlight.

Overall, photoprotective strategies aim to balance light utilization with protection against photodamage, and the term is used across biology, medicine, and materials science to describe protective functions, agents, or strategies.