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1. (Article ID: 10631)
 
Nielsen JK, Olsen CE, Petersen MK
Acylated flavonol glycosides from cabbage leaves
Phytochemistry 34 (1993) 539-544
 

Seven flavonol glycosides were isolated from a leaf extract of cabbage and characterized by chemical and spectroscopic methods including 1H and 13C NMR and negative ion FAB-MS. Five compounds were new Natural products or were fully characterized for the first time. They are derivatives of kaempferol-3-O-β-D-sophoroside-7-O-β-D-glucoside acylated at C-2"' with either caffeic acid, p-coumaric acid or ferulic acid, and of quercetin-3-O-β-D-sophoroside-7-O-β-D-glucoside acylated with either caffeic acid or ferulic acid. Kaempferol-3-O-β-D- sophoroside-7-O-β-D-glucoside and kaempferol-3-O-β-D-(2-sinapoylsophoroside)-7-O-β-D-glucoside were found for the first time in cabbage, but they have previously been found in other Brassica species.

acylated, flavonol glycosides, Brassica oleracea, Cruciferae, cabbage, caffeoyl, p-coumaroyl, feruloyl, sinapoyl

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2. (Article ID: 11406)
 
Wilson KE, Wilson MI, Greenberg BM
Identification of the flavonoid glycosides that accumulate in Brassica napus L. cv. Topas specifically in response to ultraviolet B radiation
Photochemistry and Photobiology 67(5) (1998) 547-553
 

We have shown in previous work that Brassica napus synthesizes epidermal flavonoids in response to UVB radiation (290-320 nm) and that these compounds are effective at screening the leaf mesophyll from UVB (Wilson and Greenberg, Photochem. Photobiol, 57, 556-563, 1993), This route of acclimation is common to many plant species. However, flavonoids are a highly diverse group of compounds that vary greatly from species to species, and little is known about the specific flavonoids synthesized in response to UVB, To address this, we extracted flavonoids from the leaves of B. napus plants exposed to photosynthetically active radiation (PAR: 400-700 nm), PAR + UVA (320-400 nm) and PAR + WA + UVB, The compounds were resolved by HPLC and their structures were elucidated. Twelve distinct flavonoid glucosides with quercetin and kaempferol backbones were found. In some cases, a hydroxycinnamic acid moiety was linked via an ester bridge to a glucose. Of the 12 compounds identified, the leaf concentrations of 6 increased in response to UVB: kaempferol-3-O-sophoroside (K2), kaempferol-3-O-sophoroside-7-O-glucoside (K3), quercetin-3-O-sophoroside (Q2), quercetin-3-O-sophoroside-7-O-glucoside (Q3), K3-coumaroyl ester and Q3-caffeoyl ester, Of these six compounds, K2, K3, Q2 and Q3 accumulated to high enough concentrations to contribute to UVB screening. Interestingly, the extractable amounts of the other six compounds identified were lower in the plants exposed to UVA or WA + UVB compared to plants exposed only to PAR. Thus, in B. napus UV exposure seems to cause a shift in the population of flavonoid glycosides, with four of the UVB-induced flavonoids being generated in high concentrations.

sensitivity, protection, Plants, UV-B, penetration, epidermal-transmittance, secale-cereale, rye seedlings, primary leaf, acclimation

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