Flavonol glycosides in Dyssodia tagetiflora and its temporal variation, chemoprotective and ameliorating activities.

Dyssodia tagetiflora is known as 'Tzaracata' and 'flor de muerto'. Recently, D. tagetiflora has been reported to have antioxidant activities in its polar extracts as well as insecticidal activities. Hyperoside (1), avicularin (2) and avicularin acetate (3) have been isolated previously. However, the temporary variation in glycoside flavonoids biosynthesis, as well as antibacterial and chemoprotective activities, have not been reported. The amount of 1, 2 and 3 in the different collections was characterized by HPLC-MS. Two new C-glycosides were characterized, quercetin-4'-methyl ether 6-C glucoside (A1) and quercetin-4'-methyl ether 8-C glucoside (A2), as well as [2-(3,4-dihydroxyphenyl)-5,7-dihydroxy-4-oxochromen-3-yl]3,4,5-trihydroxyoxane-2,6-dicarboxylate (A3). This is the first report of the presence of C-C flavonoid glycosides compounds in the genus Dyssodia. Hyperoside was the majority compound at all collections. The methanolic extracts of August 2016 and October 2017 were active against Micrococcus luteus and Bacillus subtillis. The methanolic extract has chemoprotective effects because, when applied topically in SKH-1 mice, it decreases the severity of epidermal damage induced by acute exposure to ultraviolet radiation. In addition, cutaneous photocarcinogenesis was decreased in mice treated with the extract. The methanolic extract of D. tagetiflora has chemoprotective properties by decreasing the damage caused by acute and chronic exposure to UV in mice.