Abstract: This study aimed to investigate and correlate the bioactive components and antioxidant activity of flowers from five varieties of Hibiscus syriacus and different polar solvent extracts from Hibiscus syriacus L. for the purpose of providing a theoretical basis for deep processing and breed of hibiscus flower. The bioactive components were identified by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The results showed that the contents of total polyphenols and total flavonoids in five varieties of Hibiscus syriacus were consistently in the decreasing order of Hibiscus syriacus L., Hibiscus syriacus f. paeoniflorus, Hibiscus syriacus cv. Lavandula Chiffon, Hibiscus syriacus cv. Shigyoku and Hibiscus syriacus f. elegantissimus. A similar order was observed in the antioxidant activity. The contents of polyphenols and total flavonoids in the flower of Hibiscus syriacus L. were the highest, which were 17.33 and 12.68?mg/g, respectively, and it had the strongest antioxidant activity with ferric ion reducing antioxidant power (FRAP), 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging capacity, and 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt? (ABTS) radical scavenging capacity of 1.58?mmol/g, 6.82 and 17.96?mg/g, respectively. There was a significant correlation between the antioxidant activity and the contents of total polyphenols and total flavonoids (P < 0.01), but the correlation with anthocyanin content was not significant (P > 0.05). All solvent extracts from Hibiscus syriacus L. had antioxidant activity. The highest total reducing power (6.16 mmol/g) was observed in the n-butanol extract, accompanied by the strongest DPPH radical (15.50?mg/g) and ABTS radical scavenging capacity (40.71?mg/g). Eight compounds from the n-butanol extract were identified including kaempferol-O-hexose-C-glucoside, apigenin, kaempferol-O-hexose-C-hexose glycoside isomers, apigenin-C-diglycoside, apigenin-glycoside glucoside, behenylphenol-3-O-rutinoside, apigenin-7-O-rutinoside, and cyanidin-3-malonyl glucoside.

Key words: hibiscus flower, total polyphenols, total flavonoids, antioxidant activity