Effect of chlorogenic acid on antioxidant activity of Flos Lonicerae extracts

Abstract

Flos Lonicerae is a medically useful traditional Chinese medicine herb. However, little is known about the antioxidant properties of Flos Lonicerae extracts. Here the antioxidant capacity of water, methanolic and ethanolic extracts prepared from Flos Lonicerae to scavenge 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and reduce Fe(3+) to Fe(2+) is examined. Chlorogenic acid, a major component of Flos Lonicerae, is identified and further purified from 70% ethanolic extract with high performance liquid chromatography (HPLC) and its antioxidant capacity is characterized. The total phenolic compounds and chlorogenic acid contents in Flos Lonicerae are determined. The present results demonstrate that the Flos Lonicerae extracts exhibit antioxidant activity and chlorogenic acid is a major contributor to this activity.

Figures

Fig. 1

HPLC analysis. The HPLC profiles (a), (b), and (c) represent the identification of chlorogenic acid in water, methanolic and 70% ethanolic extracts from Flos Lonicerae respectively. The HPLC profile (d) represents purified chlorogenic acid from 70% ethanolic extract with HPLC. There are several contaminant constituents in the prepared chlorogenic acid fraction around chlorogenic acid peak which are caused by manual collection during purification. The peaks labelled with CGA are chlorogenic acid because the retention time was identical with that of chlorogenic acid standard (e) (13.97 min). Ten micrograms the samples (a), (b), (c), (d) were respectively loaded into the HPLC system except chlorogenic acid standard (5 μg)

Fig. 2

Determination of the antioxidant capacity of Flos Lonicerae crude extracts. (a) Determination of the antioxidant capacity of Flos Lonicerae extracts to scavenge DPPH radical; (b) Determination of the antioxidant capacity of Flos Lonicerae extracts to reduce Fe3+ to Fe2+ WE, EE, ME, Vc and Ctrl stand for Flos Lonicerae water extract, 70% ethanolic extract, methanolic extract, ascorbic acid and methanol control, respectively. Results are mean of three parallel measurements and calculated with MS Excel software

Fig. 2

Determination of the antioxidant capacity of Flos Lonicerae crude extracts. (a) Determination of the antioxidant capacity of Flos Lonicerae extracts to scavenge DPPH radical; (b) Determination of the antioxidant capacity of Flos Lonicerae extracts to reduce Fe3+ to Fe2+ WE, EE, ME, Vc and Ctrl stand for Flos Lonicerae water extract, 70% ethanolic extract, methanolic extract, ascorbic acid and methanol control, respectively. Results are mean of three parallel measurements and calculated with MS Excel software

Fig. 3

The structure of chlorogenic acid

Fig. 4

Determination of the antioxidant capacity of preparative chlorogenic acid from Flos Lonicerae extract. (a) The antioxidant capacity of the samples to scavenge DPPH radical; (b) The antioxidant capacity of the samples to reduce Fe3+ to Fe2+ EE, PCGA, CGA, Vc and Ctrl stand for Flos Lonicerae 70% ethanolic extract, preparative chlorogenic acid, chlorogenic acid standard, ascorbic acid and methanol control. Results are mean of three parallel measurements and calculated with MS Excel software

Fig. 4

Determination of the antioxidant capacity of preparative chlorogenic acid from Flos Lonicerae extract. (a) The antioxidant capacity of the samples to scavenge DPPH radical; (b) The antioxidant capacity of the samples to reduce Fe3+ to Fe2+ EE, PCGA, CGA, Vc and Ctrl stand for Flos Lonicerae 70% ethanolic extract, preparative chlorogenic acid, chlorogenic acid standard, ascorbic acid and methanol control. Results are mean of three parallel measurements and calculated with MS Excel software

Fig. 5

Reaction kinetics of DPPH radical scavenging (a) and ferric reducing (b) Results are mean of three parallel measurements and calculated with MS Excel software

Fig. 5

Reaction kinetics of DPPH radical scavenging (a) and ferric reducing (b) Results are mean of three parallel measurements and calculated with MS Excel software