Polyphenols - Flavonoids Part 2

Question 1

What are Chalcones?

Answer 1

Chalcones
* Open ring as central structure, yellowish.
* Liquorice has several chalcones: anti-parasitic, antioxidant and anticarcinogenic (butein, isoliquiritigenin, licochalchalcone A).
* Isoliquiritigenin is one specific type of chalcone in liquorice - research shows it is: anti-inflammatory, antimicrobial, anti-oxidative, anticancer, cardioprotective, antitumor, antidiabetic.
* Also shown to have hepatoprotective, immunoregulatory

Question 2

How do chalcones present in Hops?

Answer 2

• “Prenylated* chalcones in hops - prenylation is the addition of hydrophobic groups
• There are two types found in hops, Xanthohumol and 8-prenylnaringenin - tests in vitro show they: inhibits aromatase (enzyme), decrease breast cancer
  cell line proliferation, induces apoptosis.
• **8-prenylnaringenin: ** This is a potent oestrogen agonist (oestrogenic activities, similar to soya),

There are two oestrogen receptors, alpha receptors and beta receptor
* Weakly mimics 17b-oestradiol
* Clinical study: showed it had a beneficial effect for vasomotor and other menopausal symptoms.
* Slightly uterotrophic
* Oestrogenic effect on mammary gland.
* Another prenylated chalcone (6-DMA-N) in
hops is strongly anti-androgenic.

Studies on Xanthohumol found
* Broad-spectrum cancer chemopreventive, in vitro studies.
* Antibacterial in vivo/in vitro - often used in the gut.
* Anti-inflammatory, antioxidant, protective against DNA damage, hypoglycaemic and hepatoprotective.
* Inhibits development/ progression of
non-alcoholic fatty liver disease, obesity,
dysregulation of glucose metabolism and
other components of the metabolic
syndrome.

Bone density and hops
* A study showed greater bone density in women beer drinkers - there is also silica in hops too
* in vitro and in vivo studies show E2-like effects on osteogenic differentiation.

Question 3

What are Flavanols?

Answer 3

Flavanols
* Hydroxyl group attached to C3 of the saturated central ring.
* Examples are Epicatechin and catechins found originally in the acacia tree (Acacia catechu).

Flavanols (Flavan-3-ols) - Flavanols can join up together: to become proanthocyanidins OPCs, and potentially larger polymers (condensed tannins).
Epicatechin derivatives and OPCs are mild to
moderate astringents, pseudotannins. Green tea contains these.

Flavanol properties, most research done on catechins:
* Antioxidant, antiangiogenic, proapoptotic properties
* Anticancer (green tea is good), anti-atherosclerotic, antihypertensive and cardioprotective; may prevent metabolic syndrome.
* Inhibitory against carcinogenesis and
cancer cell growth in vitro.
* Clinical studies: some results for the
cancer preventive activities of tea
catechins.

Question 4

What are Flavanones?

Answer 4

• Ketone functional group on central ring, lack a double bond between C2 and C3; a typical example is Vitamin P (=permeability factor).
• Hesperetin (glycoside: hesperidin);
  naringin in citrus fruits; liquiritigenin
  (glycoside: liquiritin) antioxidant in
  liquorice.
• Found to regulate capillary permeability and tonify blood vessels, preventing oedema associated with inflammation and stasis, confirmed by clinical trials.

Hesperetin (glycoside hesperidin) research: Anti-cancer, cancer chemopreventive, antioxidant, anti-inflammatory, lipid-lowering, insulin-sensitizing.
* Preclinical and clinical studies show: Beneficial in heart failure, myocardial ischemia / infarction, hypertension (randomised, controlled trial), diabetes and dyslipidemia (anti-platelet and anticoagulant effects).
* Also found to be neuroprotective, antidepressant, positive effects on
memory
* In vitro - found to have antiviral against coronaviruses including SARS.

Naringin, a flavanone glycoside
* Tomatoes, grapefruits, and citrus fruits.
* Cytochrome p-450 inhibitor effect - can potentially decrease the metabolism of certain drugs
* Found to be antioxidant, anti-inflammatory, anticarcinogenic.
* In vitro and in vivo studies: useful in
atherosclerosis (lowering plasma triglycerides and cholesterol), diabetes mellitus, neurodegenerative disorders, osteoporosis, and rheumatological disorders,
* Chemopreventive and anticancer (in models of oral, breast, colon, liver, lung, and ovarian cancer).

Question 5

What are Flavones?

Answer 5

Flavones
* Central ring has a ketone functional group, but lacks the hydroxyl group of the flavonols; double bond between C2 and
C3 (single in flavanones).
* Anti-inflammatory, anticarcinogenic, antioxidant, antispasmodic and
antimicrobial.

Flavones: the example Luteolin
* Peppers, dandelion flowers and leaves, lemon balm, peppermint, parsley, rosemary, thyme, oregano, red peppers, artichoke, celery and chamomile.
* Luteolin is anticarcinogenic in vitro:
prevents tumour development largely by
inactivating several signals and
transcription pathways essential for
cancer cells.
* Flowers of dandelion: luteolin - antioxidant and cancer prevention effect in vitro

Flavones: Apigenin (glycoside apiin)
* In parsley (Apiaceae); antiinflammatory and antispasmodic, antioxidant and anticancer
properties.
* Epidemiologic studies of diet rich in flavones: decreased risk of certain cancers (breast, digestive tract, skin, prostate and certain
haematological malignancies).
* Antioxidant.

Apigenin and luteolin - In vivo and ex vivo:
* Inhibits auto-immune T-cell responses.
* Protective effect on insulin-secreting cells.
* Anxiolytic properties.
* Chrysin in passion flower, common skullcap: neuroprotective and suppresses neuroinflammation, improves cognitive
decline; anti-amyloidogenic and neurotrophic effects.
* Beneficial effects on depression and
epilepsy.

Baicalein: found in Scutellaria baicalensis and Scutellaria lateriflora
* In vivo and in vitro: antioxidant,
cardiovascular protection, hypotensive, antimutagenic, antiinflammatory, anti-thrombotic, antiproliferative and anti-mitogenic.
* Whole extract of Scutellaria baicalensis: inhibited cancer cell growth and anti-inflammatory
* In vivo reduced prostate tumour
volume.