Pueraria extract is made of Pueraria lobata (Willd.) Ohwi roots, which contains a variety of active ingredients, mainly isoflavones, especially puerarin. Clinical research data show that pueraria extract has a significant prevention and treatment of cardiovascular diseases and anti-cancer and other pharmacological effects. Cardiovascular disease and cancer are closely related to free radicals. Therefore, the scientists screened the hydroxyl radical (· OH) model by Fenton reaction and the superoxide anion radical model by autoxidation of pyrogallol. After studying the scavenging effect of pueraria extract(ethanol), pueraria extract(water) and puerarin · OH, the results and analysis are listed below:

1 Determination of puerarin
Puerarin is one of the main active ingredients of pueraria extract. In order to determine if puerarin is an important factor of free radical scavenging, the puerarin content of each kind of pueraria extract is evaluated. The content of puerarin in pueraria extract(water) and pueraria extract(alcohol) was determined by HPLC. The results showed that the content of puerarin in pueraria extract(water) was 18.98%, pueraria extract(ethanol) was 4.32%, indicating puerarin of pueraria water extract is much higher than alcohol extract.

2 Pueraria extract of · OH scavenging effect
Hydroxyl radical is the most active free radical, its reaction rate is extremely fast, it is also the free radicals hurting the body the most. At concentration range 12.50-100 mg/L, all the three extracts had the ability to scavenge · OH radicals. With higher concentration, the scavenging effect of pueraria extracts on · OH increased gradually, but when the concentration was increased to a certain value, the scavenging effect of three kinds of extracts on · OH was not obvious. In the same concentration, the order of · OH removal: puerarin> pueraria extract(water)> pueraria ethanol extract. This result mainly depends on puerarin content. The puerarin content of pueraria extract(water) was significantly higher than alcohol extract, so the· OH scavenging effect of pueraria extract(water) was significantly higher than alcohol extract. At the concentration of 50mg/L the ·OH, the cleaning rate of puerarin and pueraria extract(water) was 40.6; 9% and 27.48% separately. At the concentration of 75mg/L, the cleaning rate of pueraria alcohol extract was 14.66%.

3 O2– scavenging effect
Pyrogallol oxidation is a method for determining scavenging activity. Under basic conditions, pyrogallol undergoes an oxidation reaction to form O2– and non-ferrous products which have a characteristic absorption peak at 325 nm. When scavenger is added, the formation of O2– is inhibited and the oxidation of pyrogallol is blocked. The absorption peak at 325 nm decreased. Therefore, the material removal ability can be determined by measuring the value of A325.

The scavenging O2– effect of all the three pueraria extracts increases with higher concentration, at the same concentration, the ability order: puerarin> pueraria extract(water)> pueraria alcohol extract. Pueraria alcohol extract showed some scavenging effect at higher concentration, it showed obvious dose-response relationship in the experimental concentration range. The scavenging effect of pueraria extract(water) is not obvious in the concentration range of 11.11~111.11 mg/L, but when the concentration exceeds 166.67 mg/L, its scavenging significantly increased. When the concentration increased from 166.67 mg/L to 222.22 mg/L, the scavenging rate increased rapidly from 11.30% to 26.15%. Puerarin had the strongest scavenging effect on O2–, which showed scavenging effect even at low concentration. When the concentration was increased from 55.56 mg / 111.11mg/L, the scavenging rate increased from 10.48% to 38.71%. The previous test results show that puerarin from pueraria extract(water) is much higher than pueraria alcohol extract, puerarin performs better cleaning O2–, so pueraria water extract is more efficient than alcohol extract possibly due to its high puerarin content.

Conclusion and discussion
Experiments show that pueraria extracts have some scavenging effect on · OH and O2–, the ability order to scavenge free radicals: puerarin> pueraria extract(water)>pueraria ethanol extract. Puerarin and pueraria extract(water) have good scavenging effect on hydroxyl radicals at the concentration of 50 mg/ml, the scavenging rate was 40.69% and 27.48%. The optimum concentration of pueraria ethanol extract for hydroxyl radical scavenging was 75 mg/ml and the scavenging rate was 14.66%. Modern medical research shows that the pathogenesis of cardiovascular diseases and cancer is closely related to free radicals. Free radicals attack the unsaturated fatty acids in the arterial wall and serum to produce peroxidative lipids and lipid peroxidation. The test shows that pueraria extract has a strong antioxidant effect, which can enhance the body’s defense against free radical damage, puerarin is especially powerful in the treatment of cardiovascular and cerebrovascular diseases.