title: Onion extract (Allium cepa L.), quercetin  and catechin up-regulate paraoxonase 1  activity with concomitant protection against  low-density lipoprotein oxidation in male  Wistar rats subjected to oxidative stress.
abstract: BACKGROUND
  Paraoxonase 1 (PON1) protects the oxidative modification of low-density lipoprotein (LDL) and is a major anti-atherosclerotic protein component of high-density lipoprotein. We explored the effect of onion extract and flavonoids (quercetin and catechin) in the regulation of PON1 expression and correlating with oxidised LDL levels in male Wistar rats subjected to mercuric chloride (HgCl₂) induced oxidative insult. Rats were divided into eight groups: Control, Experimental (HgCl₂), Experimental + onion/catechin/quercetin, Positive control (Normal + onion/catechin/quercetin). Treatment continued for 4 weeks.
  
  
  RESULTS
  PON1 activity and radical scavenging activity decreased in the Experimental group (P < 0.001) with increased susceptibility of LDL for oxidation and plasma malondialdehyde levels (P < 0.001). Onion extract significantly attenuated the adverse effects of HgCl₂ by up-regulating PON1 activity (P < 0.05), radical scavenging activity (P < 0.01), and protected against LDL oxidation (P < 0.001) and lipid peroxidation (P < 0.01). Similar effects were observed with quercetin and to a lesser extent with catechin.
  
  
  CONCLUSIONS
  The findings may explain the anti-atherosclerotic effect of onion and also foods containing quercetin and catechins.
authors.forename: Nidhi
authors.initials: N
authors.lastname: Jaiswal
authors.forename: Syed Ibrahim
authors.initials: SI
authors.lastname: Rizvi
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000009:adverse effects / Q000627:therapeutic use*; D043303:Aryldialkylphosphatase / Q000097:blood / Q000737:chemistry; D050197:Atherosclerosis / Q000097:blood / Q000201:enzymology / Q000517:prevention & control*; D015415:Biomarkers / Q000097:blood; D002392:Catechin / Q000009:adverse effects / Q000627:therapeutic use*; D019587:Dietary Supplements / Q000009:adverse effects; D007194:India; D015227:Lipid Peroxidation; D008077:Lipoproteins, LDL / Q000032:analysis / Q000037:antagonists & inhibitors; D008297:Male; D019697:Onions / Q000737:chemistry* / Q000191:economics; D018384:Oxidative Stress; D008517:Phytotherapy / Q000009:adverse effects; D010936:Plant Extracts / Q000009:adverse effects / Q000627:therapeutic use*; D018517:Plant Roots / Q000737:chemistry; D011794:Quercetin / Q000009:adverse effects / Q000627:therapeutic use*; D011897:Random Allocation; D017208:Rats, Wistar; D015854:Up-Regulation
chemical_list: D000975:Antioxidants; D015415:Biomarkers; D008077:Lipoproteins, LDL; D010936:Plant Extracts; C099252:oxidized low density lipoprotein; D002392:Catechin; D011794:Quercetin; C572204:Pon1 protein, rat; D043303:Aryldialkylphosphatase