Qualitative And Quantitative Analyses Of The Major Bioactive Compounds On Scavenging Free Radical In Flower And Leaves Of Forsythia Suspensa

The present study showed that the mechanism of tumor, aging, and cardiovascular disease and other chronic diseases is closely related with the excessive free radicals or free radical scavenging capacity decline. In order to remove excess free radicals of the body, the antioxidants were discovered. In general, the synthetic antioxidants are used widely, but the synthetic antioxidants gradually were excluded by people due to the potential toxicity of synthetic antioxidants and carcinogenic effects. Therefore, the natural, high efficiency, low toxic antioxidants from the plants are attracting a lot of attention, and become the research focus.Lian-Qiao, derived from the fruits of Forsythia suspensa (Thunb.) Vahl (Oleaceae), is a well-known traditional Chinese medicine. It has been widely used as an antipyretic, detoxicant and anti-inflammatory agent for the treatment of various infectious diseases. But a lot of Forsythia suspensa leaves are being abandoned. Forsythia suspensa leaves is used as tea in Shanxi, Hebei and Henan. Previous research also showed that the extraction of Forysthia suspensa leaves had strong anti-oxidation and anti-obesity effect. In order to develope and apply this natural source adequately, the major bioactive compounds on scavenging free radical in flower and leaves of Forsythia suspensa were qualitatively and quantitatively analyzed.Forsythia suspensa flower, leaves were collected during March 2008 to October 2008, and dried, ground, sieved. The sample powder was defatted and extracted with 60% methanol by ultrasound-assisted method. The DPPH and ABTS scavenging activies of Forysthia suspensa flower and leaves were evaluated by comparing with the fruits of Forsythia suspensa. The major bioactive compounds on scavenging DPPH radical were identified by using HPLC-DPPH off-line method. And then the content of the major bioactive compounds on scavenging radical in flower and leaves of Forsythia suspensa was determined. The results are as follows:1 The DPPH and ABTS radical scavenging activities of Forysthia suspensa flower and leaves in different growing period were higher than that of the fruits of Forysthia suspensa. And the leaf of Forysthia suspensa in March showed the strongest DPPH and ABTS scavenging activies. This suggests that the Forysthia suspensa leaf in March can be considered as a valuable source of antioxidant products.2 A high performance liquid chromatography (HPLC) was established to analyze the major bioactive compounds in Forysthia suspensa flower and leaves. The HPLC assay was performed on a Supelcosil C₁₈ column (250 mm×4.6 mm i.d., 5μm) with gradient elution of methanol and 0.8% aqueous acetic acid. Gradient elution was as follows: initial 0–6 min, linear change from A–B (75:25, v/v) to A–B (70:30, v/v); 6–24 min, linear change to A–B (65:35, v/v); 24–29 min, linear change to A–B (61:39, v/v); 29–39 min, linear change to A–B (55:45, v/v); 39–50 min, linear change to A–B (40:60, v/v). The detection wavelength was 280nm. The column temperature was set at 25℃. The flow rate was 1.0 ml/min and sample injection volume was 5μL.3 The free radical scavenging compounds in Forysthia suspensa flower and leaves were identified by using HPLC-DPPH off-line method. The results showed that compounds 1, 2, 3, 4, and 6 had free radical scavenging activity. From the retention features, UVλmax, and m/z values, the major bioactive compounds were identified as chlorogenic acid (1), forsythoside (4), and rutin (6). Moreover, peak 8 was identified as phillyrin.4 The content of chlorogenic acid, forsythiaside, rutin and phillyrin in Forysthia suspensa flower and leaves was determined. The results showed that the Forysthia suspensa leaves in March had the maximum chlorogenic acid and phillyrin content, and the highest levels of rutin was found in Forysthia suspensa flower. For forsythiaside, the content in the growth of medium-term of Forysthia suspensa leaves was higher than that in other growing peroid.In conclusion, the Forysthia suspensa leaf in March showed the strongest DPPH and ABTS scavenging activies and the highest chlorogenic acid content. The data indirectly indicated that the Forysthia suspensa leaf in March can be considered as a valuable source of antioxidant products and chlorogenic acid play a more important role in scavenging free radical of Forysthia suspensa leaves.