Rosemary has Anti-Carcinogenic Properties

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Rosemary

 

Rosemary has Anti-Carcinogenic Properties

Cindy L. A. Jones, Ph.D.

Published in Nutrition Science News, 1998.

http://sagescript.tripod.com/id45.htm

 

The same rosemary (Rosmarinus officinalis L.) used by the Romans to improve

memory is also under investigation as a potent anti-cancer therapy. These

anti-cancer properties are probably associated with rosemary=s anti-oxidant

property, which is more effective than typical food additives such as BHT and

BHA (tert-butyl-4-hydroxytoluene and tert-butyl-4-hydroxyanisol).1 Additionally,

rosemary has anti-inflammatory activity, an activity that researchers are now

finding often correlates with anti-cancer activity. This was demonstrated in an

experiment that showed that carnosol, a component of rosemary, was able to

reduce the amount of nitric oxide production in mice cells.2 Nitric oxide, which

is released during inflammation, is a free radical that can damage DNA. Because

cancer is often associated with states of chronic inflammation, some physicians

recommend anti-inflammatory drugs such as aspirin and sulindac for the

prevention of colon cancer. Active constituents of rosemary include

carnosol, carnosic acid, ursolic acid, betulinic acid, rosmaridiphenol and

rosmanol, most of which are present in the essential oil fraction.

 

 

Several studies have indicated that rosemary can prevent the binding of cancer

causing chemicals (carcinogens) to cellular DNA. Binding of a carcinogen to DNA,

leads to mutations in the DNA, and is an early step in the development of

cancer. In one report, researchers compared the effects of whole rosemary

extracts with the purified rosemary components, carnosol and ursolic acid, on

breast cancer in rats. They found that whole rosemary extract given in the diet

prevented the binding of the known carcinogen, 7,12-dimethylbenz[a]anthracene,

(otherwise known as DMBA) to DNA in breast cells.4 Carnosol was also able to

prevent binding, but to a lesser extent, whereas ursolic acid had little effect.

Similar results were seen in the actual formation of breast tumors in these rats

with both rosemary and carnosol decreasing tumor formation by 37%, while the

groups receiving ursolic acid showed little reduction in the amount of tumors

formed. These results are similar to previous results

showing that rosemary extracts can decrease skin tumors in mice caused by

certain carcinogens.

 

 

These results were confirmed by a later study also showing that rosemary could

prevent breast cancer caused by administration of DMBA. Rats fed 1% rosemary in

their diet for two weeks prior to the administration of DMBA had 76% less of the

carcinogen bound to DNA compared to rats fed a control diet.5 This effect was

also present when excess fat was added to the diet which increased the amount of

carcinogen bound to DNA. High fat diets are known to be associated with a higher

risk for breast cancer. Significant effects were also seen with only 0.5%

rosemary in the diet. Similar results have been found using human bronchial

cells and liver cells. In these experiments the DNA binding of the carcinogens

aflatoxin and benzo(a)pyrene were also shown to be inhibited by rosemary

extract. This indicates that the protective effect of rosemary is not just

associated with DMBA and probably goes beyond just breast cancer.

 

 

Besides acting by preventing binding of carcinogens to the DNA, rosemary can

also affect the metabolism of some carcinogens in a way that decreases their

toxicity. Enzymes found in the liver, known as P450, glutathione S-transferases

(GSH), and quinone reductases (QR) can affect the toxicity of some chemicals.

Although the main role of the liver P450 enzymes is to detoxify compounds, the

aromatic hydrocarbons such as DMBA are actually activated into much more potent

carcinogens. Thus, DMBA, benzo[a]pyrene and aflatoxin are considered

pro-carcinogens rather than direct acting carcinogens. The second group of

enzymes, GSH and QR, act by detoxifying these active carcinogenic metabolites

and thus protect against cancer. When rats were fed diets containing whole

rosemary extract, the enzymes GST and QR were increased significantly compared

to controls. 6 Animals fed carnosol in their diet did not exhibit an increase in

these liver enzymes. These experiments show that rosemary has a

protective effect by increasing the amount of enzymes that the liver uses for

detoxification of cancer causing chemicals, and that the effect of whole

rosemary is greater than that of its component, carnosol.

 

 

Similar experiments using human bronchial cells and liver cells in tissue

culture have shown that rosemary extract, carnosol and carnosic acid were all

able to reduce the levels of P450 enzymes after treatment with benzo(a)pyrene or

aflatoxin B1.7 In bronchial cells, rosemary extract, carnosol and carnosic acid

were able stimulate the QR and GST enzymes after treatment with benzo(a)pyrene.

Therefore, by decreasing the enzymes that can convert procarcinogens to a more

potent carcinogen and increasing enzymes that can inactivate carcinogens,

rosemary components have a protective effect on cancers.

 

 

In summary, two separate mechanisms have been identified to explain the

anti-carcinogenic properties of rosemary; blocking carcinogen binding to DNA,

and modifying metabolic enzymes to decrease the toxicity of a carcinogen.

Although the anti-cancer properties of rosemary have been clearly demonstrated

in animal studies, these have not yet led to human trials. Since whole rosemary

seems to be as beneficial or more beneficial than isolated components that have

been examined to date, the addition of rosemary to one=s diet may have more

benefit than just as a food flavoring or preservative.

 

 

 

1. Chan, M. M-Y. Ho C-T. And Huang, H-I. Effects of three dietary phytochemicals

from tea, rosemary and turmeric on inflammation-induced nitrite production.

Cancer Letters 96:23-29, 1995.

2. Offord, E.A., Mace, K., et al., ARosemary components inhibit

benzo(a)pyrene-induced genotoxicity in human bronchial cells. Carcinogenesis

16:2057-2062.

3. Ho, C-H, Ferraro, T., et al, A Phytochemicals in tea and rosemary and their

cancer-preventive properties,@ In Ho, C-T, Osawa, T., et al ed., Food

Phytochemicals for Cancer Prevention II:2-19. Washington, DC: American Chemical

Society, 1994.

4. Amagase, H., Sakamoto, K., et al, Dietary rosemary suppresses

7,12-dimethylbenz(a)anthracene binding to rat mammary cell DNA. J. Nutr.

126:1475-1480, 1996.

5. Singletary, K., MacDonald, C., and Wallig, M. Inhibition by rosemary and

carnosol of 7,12-dimethylbenz[a]anthracene (DMBA)-induced rat mammary

tumorigenesis and in vivo DMBA-DNA adduct formation. Cancer Letters 104:43-48,

1996.

6. Singletary, K.W., Rosemary extract and carnosol stimulate rat liver

glutathione-S-transferase and quinone reductase activities. Cancer Letters

100:139-144, 1996.

7. Offord, E. A., Mace, K. Et al. Mechanisms involved in the chemoprotective

effects of rosemary extract studied in human liver and bronchial cells. Cancer

Letters 114:275-281, 1997.

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