Defense potential of secondary metabolites in medicinal plants under UV-B stress

• Published in: Journal of photochemistry and photobiology. B, Biology Vol. 193; pp. 51 - 88
• Main Authors: Takshak, Swabha, Agrawal, S.B.
• Format: Journal Article
• Language: English
• Published: Switzerland Elsevier B.V 01.04.2019; Elsevier BV
• Subjects: Alkaloids; Animal health; Animal models; Animals; Cell lines; Cosmetics; Defense potential; Functional foods & nutraceuticals; Herbal medicine; Irradiation; Medicinal plants; Metabolites; Ozone depletion; Pharmaceuticals; Plant protection; Radiation damage; Reactive nitrogen species; Reactive oxygen species; Secondary metabolites; Sun screens; Sunscreens; Terpenes; Ultraviolet radiation; UV-B radiation; Defense potential; Medicinal plants; Secondary metabolites; UV-B radiation
• ISSN: 1011-1344; 1873-2682
• DOI: 10.1016/j.jphotobiol.2019.02.002

Ultraviolet-B (UV-B) radiation has, for many decades now, been widely studied with respect to its consequences on plant and animal health. Though according to NASA, the ozone hole is on its way to recovery, it will still be a considerable time before UV-B levels reach pre-industrial limits. Thus, for the present, excessive UV-B reaching the Earth is a cause for concern, and UV-B related human ailments are on the rise. Plants produce various secondary metabolites as one of the defense strategies under UV-B. They provide photoprotection via their UV-B screening effects and by quenching the reactive oxygen- and nitrogen species produced under UV-B influence. These properties of plant secondary metabolites (PSMs) are being increasingly recognized and made use of in sunscreens and cosmetics, and pharma- and nutraceuticals are gradually becoming a part of the regular diet. Secondary metabolites derived from medicinal plants (alkaloids, terpenoids, and phenolics) are a source of pharmaceuticals, nutraceuticals, as well as more rigorously tested and regulated drugs. These metabolites have been implicated in providing protection not only to plants under the influence of UV-B, but also to animals/animal cell lines, when the innate defenses in the latter are not adequate under UV-B-induced damage. The present review focuses on the defense potential of secondary metabolites derived from medicinal plants in both plants and animals. In plants, the concentrations of the alkaloids, terpenes/terpenoids, and phenolics have been discussed under UV-B irradiation as well as the fate of the genes and enzymes involved in their biosynthetic pathways. Their role in providing protection to animal models subjected to UV-B has been subsequently elucidated. Finally, we discuss the possible futuristic scenarios and implications for plant, animal, and human health pertaining to the defense potential of these secondary metabolites under UV-B radiation-mediated damages. •Plants’ secondary metabolites (SMs) have defense potential against UV-B stress.•Screening and antioxidative properties are the primary defense mechanisms of SMs.•Innate defense mechanisms in animals are inadequate against current levels of UV-B.•SMs in medicinal plants protect both plants and animals against UV-B.•Medicinal plants’ SMs have futuristic implications for human health.