Pomegranate Juice Inhibits Serum Angiotensin-Converting Enzyme (ACE) Activity and Reduces Systolic Blood Pressure

The Durk Pearson & Sandy Shaw®
Life Extension NewsTM
Volume 9 No. 1 • January 2006


Pomegranate Juice Inhibits Serum Angiotensin-Converting Enzyme (ACE) Activity and Reduces Systolic Blood Pressure

A major class of drugs used in the treatment of hypertension, congestive heart failure, and myocardial infarction are inhibitors of angiotensin-converting enzyme (ACE), which converts angiotensin I to the potent vasoconstrictor angiotensin II. Interestingly, the use of ACE inhibitors has been associated with increased lower-extremity muscle mass1,1a (in older persons), with moderate attenuation of decline in physical performance2 (aged male rats), and slowed or halted decline in muscle strength3 (elderly women). In a 2001 paper,4 researchers studied the effects of pomegranate juice consumption (50 ml, about 2 ounces), 1.5 mmol of total polyphenols per day for two weeks), by hypertensive patients (seven males and three females). Mean blood pressure was initially 155±7 / 83±7 mmHg. The soluble polyphenols content of pomegranate juice varies from 0.2 to 1.0% and includes tannins, ellagic tannins, anthocyanins, catechins, and gallic and ellagic acids.

The researchers found that, as a result of drinking pomegranate juice at the dose schedule given above, there was a 36% decrease in serum ACE activity and a 5% reduction in systolic blood pressure. (Drinking 1 cup a day of the 25% pomegranate juice Langers product that we use would provide the equivalent to the 2 ounces of pomegranate juice consumed each day by subjects in this study.) The authors note that they had recently published a paper showing “potent” antiatherogenicity of pomegranate juice in healthy humans and in atherosclerotic mice and identified tannins as the components responsible for the antioxidative properties against LDL oxidation.

In another paper,5 researchers report that ACE activity was inhibited by flavan-3-ols and procyanidins, components of many plant foods, in rabbit lung. Procyanidins are a group of polymeric polyphenols composed of the flavan-3-ol units, (-)-epicatechin (epicatechin) and (+)-catechin (catechin). Procyanidins are found in foods such as nuts, cranberries, apples, red wine, tea, and cocoa or chocolate. The authors suggest that “The finding that certain flavonoid-rich foods can induce reductions in blood pressure and inhibit ACE activity, both in vivo and in vitro, opens up the possibility that consumption of select flavonoid-rich foods may mimic synthetic ACE inhibitors and provide health benefits but without adverse side effects. In this regard, it was observed that after regular consumption of a diet rich in flavan-3-ols and procyanidins for 14 days, blood pressure was significantly diminished in aged people. … It was observed that flavan-3-ols and procyanidins isolated from cocoa compete for enzyme-active sites with synthetic ACE substrates.”

In a follow-up paper6 by the same authors of Reference 5, they used solid foods (black tea, green tea, chocolate) to prepare high-procyanidin-containing extracts. In addition, they used Argentinean cabernet sauvignon, malbec, generics, and white wines from commercial sources. For example, they used 2 grams of tea in 250 ml of boiling water to prepare the black and green tea extracts. Chocolate extracts were prepared using 25 grams of chocolate (one serving) in 250 ml of hot water. The high-procyanidin and low-procyanidin chocolates were provided by Mars, Inc. Their earlier study5 had found ACE-inhibiting activity by purified flavanols and procyanidins in vitro. Now they examined the effects of procyanidin extracts prepared from commonly eaten foods on ACE activity in rat kidney membranes. Of those foods tested (and compared to captopril, an ACE inhibitor drug), high-procyanidin chocolate inhibited ACE by 70%, while low-procyanidin chocolate inhibited ACE by 45%. The most effective in inhibiting pure ACE were (in order of potency) cabernet sauvignon wine, high-procyanidin chocolate, and chocolate. Of the several polyphenols tested, only epigallocatechin (green tea is an excellent source) inhibited the enzyme with IC50 (the amount required for 50% inhibition) in the micromolar range.

As the authors concluded,6 “The occurrence of such inhibition in vivo needs to be determined; however, the association between the consumption of flavonol-rich foods and reduction in blood pressure provides an important rationale supporting this hypothesis.”

References

  1. Di Bari et al. Antihypertensive medications and differences in muscle mass in older persons: the Health, Aging, and Body Composition Study. J Am Geriatr Soc 52:961-6 (2004).
    1a. Carter et al. Angiotensin-converting enzyme inhibition intervention in elderly persons: effects on body composition and physical performance. J Gerontol 60A(11):1437-46 (2005).
  2. Carter et al. Angiotensin-converting enzyme inhibition, body composition, and physical performance in aged rats. J Gerontol: Biol Sci 59A(5):416-23 (2004).
  3. Onder et al. Relation between use of angiotensin-converting enzyme inhibitors and muscle strength and physical function in older women: an observational study. Lancet 359:926-30 (2002).
  4. Aviram, Dornfeld. Pomegranate juice consumption inhibits serum angiotensin-converting enzyme activity and reduces systolic blood pressure. Atherosclerosis 158:195-8 (2001).
  5. Actis-Goretta et al. Inhibition of angiotensin converting enzyme (ACE) activity by flavan-3-ols and procyanidins. FEBS Lett 555:597-600 (2003).
  6. Actis-Goretta et al. Inhibition of angiotensin converting enzyme activity by flavanol-rich foods. J Agric Food Chem 54:229-34 (2006).

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