Puerarin and Conjugate Bases as Radical Scavengers and Antioxidants:  Molecular Mechanism and Synergism with β-Carotene

Abstract

The 4'-hydroxyl group of puerarin, a C-glycoside of the isoflavonoid daidzein, was shown, using 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) radical cation and stopped-flow spectroscopy and by comparison with the 7-propylpuerarin (A ring derivative) and 4'-propylpuerarin (B ring derivative), to be a more efficient radical scavenger as compared to the 7-hydroxyl group by a factor of 2, a difference increasing upon deprotonation. The difference in radical scavenging agreed with the oxidation potentials (cyclic voltammetry in acetonitrile, 0.1 M Bu4NBF4 at 25 degrees C): E/mV=862+/-3 for puerarin, 905+/-10 for 7-propylpuerarin, and 1064+/-2 for 4'-propylpuerarin relative to ferrocene/ferricenium. In aqueous solution, the reduction potential was shown to decrease for increasing pH, and deprotonation of the 4'-hydroxyl group increased radical scavenging more than deprotonation of the 7-hydroxyl group. The 7-hydroxyl was found to be more acidic (pKa1=7.20+/-0.01 in puerarin and pKa=7.23+/-0.01 in 4'-propylpuerarin) than the 4'-hydroxyl group (pKa2=9.84+/-0.08 in puerarin and pKa=9.51+/-0.02 in 7-propylpuerarin); aqueous solution, ionic strength of 0.1, and 25 degrees C. In phosphatidyl choline liposome of pH 7.4, puerarin and beta-carotene each showed a modest antioxidant activity measured as prolongation of the lag phase for formation of conjugate dienes and using the water-soluble radical initiator APPH with effects of puerarin and beta-carotene being additive. For the lipophilic initiator AMVN, the antioxidative effect decreased for puerarin and increased for beta-carotene as compared to APPH and showed a clear synergism. A regeneration of beta-carotene, effective in the liposome lipid phase as antioxidant, from the cation radical by deprotonated forms of puerarin was demonstrated in 9:1 chloroform/methanol using laser flash photolysis with k2=2.7x10(4) L mol-1 s-1 for the bimolecular process between the cation radical and the puerarin dianion.

Preventive Effects of Puerarin on Alcohol-induced Osteonecrosis

“…The traditional Chinese medicine pueraria has been used to treat alcoholism for thousands of years. Recently, many observations demonstrate puerarin extracted from pueraria is antioxidative, can prevent injuries to cells due to lipid peroxidation, and can maintain the stability of the cell membrane structure by removing the oxyradicals from tissues and cells [4,6,12,13]. The protective effects of puerarin on cells are also related to calcium ion rivalry and b-receptor blockage [54].…”

Metabolic profile of puerarin in rats after intragastric administration of puerarin solid lipid nanoparticles

“…6 The molecular mechanism underlying these pharmacological benefits is believed to involve puerarin's ability to act as an antioxidant and a scavenger of reactive oxygen species. 7 In diet-induced hypercholesterolemic rats, puerarin markedly reduces the total cholesterol by the promotion of cholesterol and bile acid excretion in the liver. 6 Puerarin also improves endothelial function by inhibiting cellular factors, such as adhesive molecules 8 and C-reactive protein, 9 and stimulating endothelial nitric oxide synthase phosphorylation and nitric oxide production via activation of an estrogen receptor-mediated phosphatidylinositol 3-kinase/Akt-and calmodulin-dependent kinase II/AMP-activated protein kinase-dependent pathway.…”

Protecting Mechanism of Puerarin on the Brain Neurocyte of Rat in Acute Local Ischemia Brain Injury and Local Cerebral Ischemia-reperfusion Injury

“…Recent researches about kudzuvine root assessed its main active phar-macological component puerarin, especially in health food and cerebrovascular diseases. 17) The present research shows that puerarin has the actions of dilating the coronary artery 18) and cerebral vessels, increasing cerebral blood ‰ow, 14) modulating vascular endothelial cell function, 19) reducing blood fat and atherosclerosis, 20) scavenging free radical, 21) inhibiting ischemical reperfusion injury 22) and improving hemorheology. 23) Some researches indicate that the neuroprotection of puerarin against cerebral ischemia is associated with the prevention of apoptosis in rats.…”