Abstract:

Steam explosion pretreatment was employed on Puerariae thomsonii Radix at a steam pressure of 1.0 and
2.0 MPa for 30, 40, 60 and 80 s, respectively. In order to explore the effect of steam explosion pretreatment on the total
isoflavone content and antioxidant capacity of Puerariae thomsonii Radix, the content of total isoflavones was determined
using UV spectrophotometry. The 1, 1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity was used to evaluate
free radical scavenging capacity. The results indicated that the extraction efficiency of total isoflavones, the yield of
methanol extract and antioxidant capacity significantly increased after steam explosion. Under optimal conditions, the
yield of total isoflavones (calculated as puerarin) was 5.43 mg/g, which was 2.32 times as much as that of the untreated
sample; the yield of methanol extract was 16.92%, and the 50% inhibitory concentration (IC50) for DPPH radical scavenging
activity decreased from 30.65 g/L to 10.10 g/L, suggesting that the antioxidant capacity was improved. It can be concluded
that a proper and reasonable steam explosion pretreatment can be applied to extract the active compounds and enhance the
antioxidant capacity of Puerariae thomsonii Radix.

Key words: steam explosion, Puerariae thomsonii Radix, total isoflavones, antioxidant capacity