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Pueraria mirifica (White Kwao Keur) is a thai rejuvenating folk medicine
which contains many phytoestrogens including miroestrol, deoxymiroestrol and
insoflavonoid group (kwakhurin, daidzein, genistein, etc.) which possess estrogenic
activity. This study aimed to investigate the antioxidative effect of Pueraria mirifica
in several models both in vitro and ex vivo. Free radical scavenging assay using ESR
method, the EC50 of superoxide- and hydroxyl scavenging activity was 49.4 mg/ml
and 103 μg/ml, respectively. The scavenging ability to hydroxyl radical was 4.8 times
weaker than vitamin C. By the method of DPPH assay, the EC50 of the quenching
DPPH was 19.6 mg/ml. Antioxidant activity of ethanol extract (1mg/ml) was
equivalent to 50 μM vitamin C evaluated by ferric reducing antioxidant power
(FRAP) assay. The measurement of the resistance of low density lipoprotein (LDL)
to oxidation promoted by copper ion ex vivo, LDL prepared from
hypercholesterolemic rabbits supplemented with orally 100 mg/kg/day Pueraria
mirifica (P.mirifica-group) for 12 weeks showed a significantly decreased
susceptibility to Cu2+-mediated oxidation ex vivo, compared with
hypercholesterolemic rabbits with no supplementation (Chol-group). The lag time
was prolonged from 115.6 ± 9.7 min in Chol-group to 160.4 ± 6.6 min in P.mirifica-group.
These data demonstrate that although, Pueraria mirifica had mild
antioxidative activity in the in vitro experiment. However, it could increased the
resistance to oxidation of LDL ex vivo. Our results may provide the beneficial effect
of Pueraria mirifica for the cardiovascular system which required further
experimental and clinical studies.
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