| Flos Rosae chinensis is the flower of Rosa chinensis Jacq, which belongs to rosa genus of rosaceae family. It is commonly used in traditional medicine and has some nutritional function. The resources of Rosa chinensis Jacq is very rich in China due to its wide cultivation. Due to its potential huge economic social values, we should pay close attention on its systematic study and deep exploitation regarding its bioactive constituents.In this study, an activity-directed fractionation and purification process was used to isolate 1,1-diphenyl-2-picrylhydrazyl radical (DPPH-) scavenging components from Flos Rosae chinensis (from Nanyang, Henan).Objectives1. To determine the total flavonoids content of Flos Rosae chinensis by 95% ethanol extraction.2. To screen the DPPH·scavenging activity of the extracted parts from Flos Rosae chinensis by solvent extraction.3. To separate the extract which has the strongest DPPH·scavenging capacity, to purify the antioxidant compounds, elucidate their structures and screen the strongest DPPH·scavenging activity constituents.Methods1. Dried and powered Flos Rosae chinensis was extracted three times in 95% ethanol under reflux. The determination of total flavonoids was conducted by UV spectrophotometer.2. Dried and powered Flos Rosae chinensis was extracted three times in 95% ethanol under reflux. This extract was then filtered through absorbent gauze, and the filtrate was concentrated under vacuum to remove ethanol. The suspension was successively partitioned with petroleum ether, chloroform, ethyl acetate, n-butanol step by step. The antioxidant activity of the extracts was assayed by DPPH·scavenging experiment. The extract with the strongest DPPH·scavenging capacity was further purified.3. Some compounds of the extract were separated and purified using column chromatography over silica gel column, ODS RP column, Sephadex LH-20 column, Polyamide column and MCI column. Their structures were identified by spectroscopic methods. The antioxidant activity of these compounds was assayed by DPPH free radical scavenging experiment.Results1. The content of total flavonoids in Flos Rosae chinensis was (6.115±0.050) g of rutin equivalents in 100 g of dry material.2. The DPPH·scavenging capacity of the extracts was as follow:ascorbic acid> ethyl acetate fraction> n-butanol fraction> water-soluble fraction≈95% ethanol fraction > chloroform fraction> petroleum ether fraction. The ethyl acetate fraction had the strongest DPPH·scavenging activity.3. Ten compounds were obtained from ethyl acetate fraction of Flos Rosae chinensis. They were 3,4,8,9,10-pentahydroxydibenzo[b,d]pyran-6-one (1); quercetin (2); kaempferol (3); 3,5,7,4'-tetrahydroxy-8-methoxy-flavone (4); isoquercetrin(5); kamp-ferol 3-O-β-D-glucoside (6); tiliroside (7); kampferol 3-O-(6"-galloyl)-β-D-glucoside (8);kampferol3-O-(2",6"-digalloyl)-β-D-glucoside(9);quercetin3-O-(2",6"-digalloyl)-β-D-glucoside(10). Among them, compound 1 belonged to coumarin, and the other nine compounds belonged to flavonoids. Compounds 1,4,7,8,9 and 10 were the first time found from Flos Rosae chinensis. The descending order of DPPH radical scavenging capacity for these compounds was:10>9>1≈8>5> ascorbic acid≈2 >6>7>3>4.Conclusions1. Flos Rosae chinensis is a good source of flavonoids.2. Ten compounds are obtained from ethyl acetate fraction of Flos Rosae chinensis. Among them, compound 1 belongs to coumarin, and the other nine compounds belong to flavonoids. Compounds 1,4,7,8,9 and 10 are the first time found from Flos Rosae chinensis.3. The extracts of Flos Rosae chinensis have strong antioxidant activities, especially the middle-polar fraction (ethyl acetate fraction). Ten antioxidant compounds are isolated and identified from ethyl acetate fraction. Among them, nine compounds belong to flavonoids. This suggests that the antioxidant activity of Flos Rosae chinensis mainly depends on its content of flavonoids. Compounds 1,8,9 and 10 have the stronger antioxidant activity. |
