Polyphenols - Isoflavones and Quinones

Question 1

What are phenolic phytooestrogens?

Answer 1

We have already looked at:
* Lignans: enterodiol and enterolactone, formed by bacterial action on precursors (flaxseed).
* Flavanones: naringenin and 8-prenylnaringenin in hops
There are also:
* Isoflavones: genistein, daidzein and their glycosides (Leguminosae).

Question 2

What are Isoflavones?

Answer 2

Isoflavones
* Are isomers of flavones - mirror image of the flavones.
* Antifungal, some insecticidal.
* Often found in pea family - discovered when sheep grazing on red clover became infertile. Also found people who eat a lot of soya have reduced levels of certain cancers
* Phyto-oestrogens - A functional name – includes all constituents that can affect the oestrogen receptors. In grains, seed and legumes, important for growth and maturation, highest in sprouts.

Question 3

When are Isoflavones SERMs?

Answer 3

• Isflavones can either be oestrogenic or anti-oestrogenic effects depend on endogenous oestrogen concentration.
• Isoflavones are SERMs (selective oestrogen receptor modulators).
• In a high oestrogen environment, isoflavones cause displacement of endogenous oestrogen - has a very weak oestorgen effect compared to the endogenous environment.
• In low oestrogen environment, the isoflavones create a net oestrogenic effect as althgouhg a light effect its better than nothing.

Note, we have more than one receptor: ERα (alpha) and ERβ (beta)
* Erα – found mostly in ovarian cancer lines, and oestrogen receptor node-positive breast cancers.
* Erβ – preferentially expressed in normal breast and ovarian tissue.
* Phenolic phyto-oestrogens preferentially bind to the ER β - so preventing overstimulation of tissue.

• Some research has looked at soya’s Synergy with Tamoxifen. It found it didn’t interfere but enhanced it. Also cancer protective: antiproliferative, antiangiogenesis, antioxidant effect, tyrosine kinase inhibition and inhibits cell adhesions.

Question 4

What are the effects of isoflavones?

Answer 4

Effects of isoflavones
* Effect on bone health, cardiovascular system, and cancer prevention.
* Health benefits could be their effect on enzymes, protein synthesis, angiogenesis, cell differentiation, calcium transport and lipid
peroxidation.

Question 5

What are their pharmacokinetics?

Answer 5

Pharmacokinetics
* Usually found in the plant as glycosides which when consumed, are metabolised by intestinal flora: Biochanin A -> genistein; Formononetin -> daidzein -> equol
* Variability colonic micro.
* Dietary fat: reduces absorption of isoflavones.
* Fructo- oligosaccharides (inulin) increased the absorption.
* Urinary recovery of equol can vary greatly (15-66%) from person to person: Urinary equol producers, lower risk breast cancer. Lower concentration of androstenedione, dehydroepiandrosterone, oestrone, cortisol and testosterone, along with higher concentration of SHBG.

Question 6

What are some interesting studies?

Answer 6

Clinical studies for soy and red clover
* Soya isoflavone intake was
associated with a reduced risk of
breast cancer, and breast cancer recurrence.

Soy isoflavones and prostate cancer
* Soya isoflavone consumption is possibly protective against prostate cancer and slows
disease progression.

Cardiovascular benefits: Improvement in arterial stiffness, small reduction in blood pressure and improved flow-mediated
dilation (an indicator of cardiovascular health).

Effects of soy isoflavones in menopause
* Beneficial impact of isoflavones on bone health.
* Beneficial in the treatment of menopausal vasomotor symptoms.

Safety of soy and red clover isoflavones
* No impact on mammographic breast density in postmenopausal women.
* No oestrogenic stimulation of the endometrium when used for up to 2 years.
* Some evidence suggests that soya, by inhibiting absorption, may impact thyroid function - may increase the dose of thyroid hormone required by hypothyroid patients.

Question 7

What are Quinones?

Answer 7

Quinones
* 6-carbon ring bearing 2 opposite ketone groups
* Three types
* Are an important component of the electron transport system
* Antioxidant: the reduction to hydroquinone has been shown to play a key role in their antitumour activity.

Question 8

Where do you find Quinones?

Answer 8

One of the Quinones is Ubiquinol, which is a reduced form of ubiquinone, co-enzyme Q10.
* Found in organ meats, but also spinach, broccoli, cauliflower, peanuts and soybeans.
* The body makes it; but it diminishes with age and chronic disease.
* Statins also deplete the body of it.