Effects of boiling on the antihypertensive and antioxidant activities of onion.
This study was designed to show the effect of boiling on the antihypertensive and antioxidant activities of onion in N(G)-nitro-L-arginine methyl ester (L-NAME) induced-hypertensive rats and spontaneously hypertensive rats (SHR). Male 6-wk-old Sprague-Dawley rats were made hypertensive by being given distilled water containing L-NAME at a dose of 50 mg/kg BW/d. These rats were fed diets containing raw or boiled onion at a concentration of 5%. Raw onion significantly reduced the increase in systolic blood pressure in both L-NAME induced-hypertensive rats and SHR, and inhibited the increase in thiobarbituric acid-reactive substances (TBARS) and conjugated dienes in the plasma and tissues of SHR. The antihypertensive effect of boiled onion was not found, and the antioxidant activity of it was much weaker than that of raw onion. The excretion of nitric oxide metabolites (NOx) in urine was enhanced by raw onion in both L-NAME induced-hypertensive rats and SHR, and was enhanced by boiled onion only in SHR. In conclusion, our results suggested that the anti-hypertensive activity of onion disappeared during boiling, and the disappear of the antihy-pertensive activity of raw onion after boiling might come, in part, from a decrease of the antioxidative activity of onion, with a consequent reduction in the saving of nitric oxide (NO).
Kawamoto
Eiko
E
Graduate School of Human Life Science, Osaka City University, Sugimoto 3-3-138, Sumiyoshi-ku, Osaka 558-8585, Japan.
Sakai
Yoko
Y
Okamura
Yuko
Y
Yamamoto
Yukiko
Y
D000818:Animals; D000959:Antihypertensive Agents / Q000032:analysis / Q000737:chemistry; D000975:Antioxidants / Q000032:analysis*; D004435:Eating; D005511:Food Handling / Q000379:methods*; D006358:Hot Temperature; D006973:Hypertension / Q000139:chemically induced / Q000178:diet therapy*; D008099:Liver / Q000737:chemistry; D008297:Male; D009206:Myocardium / Q000737:chemistry; D019331:NG-Nitroarginine Methyl Ester; D009569:Nitric Oxide / Q000652:urine; D019697:Onions / Q000737:chemistry*; D051381:Rats; D011918:Rats, Inbred SHR; D017207:Rats, Sprague-Dawley; D017392:Thiobarbituric Acid Reactive Substances / Q000032:analysis; D015430:Weight Gain
D000959:Antihypertensive Agents; D000975:Antioxidants; D017392:Thiobarbituric Acid Reactive Substances; D009569:Nitric Oxide; D019331:NG-Nitroarginine Methyl Ester