Structures of UV‐B Induced Sunscreen Pigments of the Scots Pine (Pinus sylvestris L.)

Abstract

Diacylated flavonol glycosides are the response of Scots pine seedlings to UV‐B irradiation. The two induced compounds 1 and 2 both have their absorption maximum at 315 nm (ϵ = 50300) in the range of UV‐B radiation (290–320 nm), are compartmented in the epidermis, and offer much better protection than the monoacylated analogues at the same molarity.

Arabidopsis Mutants Lacking Phenolic Sunscreens Exhibit Enhanced Ultraviolet-B Injury and Oxidative Damage

“…Changes in UV-B absorbance of extracts made from plants exposed to UV cannot be assumed to be due solely to induction of flavonoids, as is common practice in the literature. An example of the importance of this principle was recently demonstrated for two closely related UV-B-absorbing compounds in Pinus sylvestris (Scots pine) seedlings (Jungblut et al, 1995). These compounds are flavonol monoglycosides that each contain two p-coumaroyl groups attached to the sugar moiety as acyl groups.…”

Acylated Flavone Glucosides: Synthesis, Conformational Investigation, and Complexation Properties

“…Beside their important biological roles in nitrogen fixation and chemical defense, flavonoids possess a broad range of pharmacological properties including anti-cancer, anti-viral, and anti-inflammatory properties [2], which may be the consequence of their antioxidant properties and their affinity for proteins, including enzymes. Flavonoids also protect plants from damaging UV-B radiation [3] and efficiently contribute to natural color expression by forming stable molecular complexes with polyphenolic pigments (anthocyanins), a phenomenon known as copigmentation [4].Most flavonoids occur in nature as glycosides in which at least one of the OH groups (most frequently, HOÀC(3), HOÀC(5), and HOÀC (7)) of the chromophore (aglycone) is glycosylated by mono-to tetrasaccharides involving neutral sugars such as d-glucose, d-galactose, l-rhamnose, and d-xylose. Acylation of sugar OH groups by a variety of aliphatic (acetic, malonic, succinic etc.)…”

“…acids brings additional structural diversity to the flavonoid family [1]. Although the possible influence of such acyl groups on the binding and antioxidant properties of flavonoids is still poorly documented, there is evidence that they play an important role in protection against UV-B radiation [3] and in pigmentation [4]. For instance, anthocyanins bearing aromatic-acid moieties typically display much more stable colors than their deacylated counterparts.…”

Flavonoid Function and Activity to Plants and Other Organisms

“…They include pollinator attractants, oviposition stimulants, feeding attractants and deterrents, allelopathy and phytoalexins. This paper reviews function and activity of flavonoids against plants and other organisms.Key words: flavonoids, pollinator attractants, feeding attractants and deterrents, allelopathy, phytoalexins di-P-coumaroylglucoside) and quercetin 3-O-(3´´,6´´-di-P-coumaroylglucoside) in Pinus sylvestris (Pinaceae) (Jungblut et al, 1995), quercetin 3-O-galactoside, myricetin 3-O-rutinoside and two P-coumaroyl kaempferol 3-Oglucoside in Quercus ilex (Fagaceae) (Skaltsa et al, 1994), and glycosides of quercetin, apigenin and luteolin in Olea europea (Oleaceae) (Karabourniotis et al, 1992) The occurrence of anthocyanins as pollinator attractants is well-known as a function of the flavonoids in plants. Additionally, it is known that flavones and flavonols, which can hardly see by human eyes, also act as pollinator attractants in addition to visible anthocyanins.…”