Photoelicitation of bioactive secondary metabolites by ultraviolet radiation: Mechanisms, strategies, and applications

Abstract

As sessile organisms, plants are exposed to various environmental factors that lead to changes in physiology and morphology. One of these factors is ultraviolet radiation. Plants have protective mechanisms, both constitutive and induced, or can activate repair responses to cope with UV-B stress. One of the most common protective responses is the accumulation of secondary metabolites capable of absorbing radiation in the ultraviolet wavelength range, such as anthocyanins, flavonols, and flavones. These compounds can also scavenge free radicals, mainly reactive oxygen species (ROS). Examples of UV-induced accumulation of compounds belonging to virtually all classes of secondary metabolites are available. Exposure to UV-B radiation stimulates expression of an array of genes involved in defense responses. Increased input of UV light has been shown to increase ROS production, activity of antioxidative enzymes, and secondary metabolite pathways in different plant species. UV is a powerful tool to modulate secondary metabolism pathways in plants. Besides field level manipulation of UV-B incidence, the use of acute treatments and UV-C pulses may be useful strategies for changing profiles and yields of plant secondary compounds of medicinal interest at commercial scale.