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quercetin is a 'bioenhancer'

Sherlock

Boswellia for lungs and MC stabllizing
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k8518704 USA
While looking for evidence as to whether the noted absorption-enhancer piperine would also enhance the absorption of quercetin, I found this paper which says that quercetin is itself a 'bioenhancer'. That's surprising because of how quercetin is said to be difficult to absorb - though maybe if quercetin is difficult to absorb then it stays in the gut and influences the absorption of other molecules.

http://www.ijabmr.org/article.asp?i...me=1;issue=1;spage=5;epage=10;aulast=Randhawa
Year : 2011
Bioenhancers from mother nature and their applicability in modern medicine

Quercetin is found in citrus fruits and is a dual inhibitor of cytochrome P 3A4 (CYP3A4) and P-gp. Quercetin has exhibited a wide range of beneficial biological activities, including antioxidant, radical scavenging, anti-inflammatory, antiatherosclerotic, a...ntitumor, and antiviral effects. [30] In a study, pretreatment of quercetin (5.0 and 15 mg/kg) half an hour before verapamil (10 mg/kg) administration significantly altered the pharmacokinetics of verapamil. Compared with verapamil alone group, the Cmax and AUC of verapamil increased approximately two times in the rabbits pretreated with quercetin. Absolute and relative bioavailability values of verapamil in the rabbits pretreated with quercetin were significantly higher (P < 0.05) than verapamil alone group. [31] Similar results have been reported with pretreatment/co-treatment of quercetin with diltiazem, [32] paclitaxel, [33] digoxin, [34] doxorubicin, [35] and tamoxifen [36] [Table 2].
IntJAppBasicMedRes_2011_1_1_5_81972_t2.jpg
Table 2: Effect of quercetin pretreatment/co-treatment on pharmacokinetic parameters of different drugs

Click here to view


The relative bioavailability of paclitaxel after administration of the prodrug to rats pretreated with quercetin was 1.25-2.02-folds higher than the prodrug control. The development of oral paclitaxel preparations as a prodrug or with quercetin is feasible, which is more convenient than the intravenous dosage forms. [33]


[piperine is in black pepper and even more-so in white pepper]

Also from that paper and of possible interest in POTS:
Piperine increases area under the curve (AUC) of... propranolol,
but an association with the much more commonly used atenolol doesn't seem to show up.
 

Little Bluestem

All Good Things Must Come to an End
Messages
4,930
They start by saying
Quercetin is found in citrus fruits and is a dual inhibitor of cytochrome P 3A4 (CYP3A4) and P-gp.
Rather than increasing absorption, it may be decreasing breakdown in the liver. Either way I suppose it would be a bioenhancer.
 

carolwxyz99

Senior Member
Messages
114
I take quercetin as a breast cancer prevention. I was advised by a nutrtional doctor to take it with bromelain before meals. I have also heard that vit C can help absorbtion of quercetin.

Interestingly I took tamoxifen for a while and hadn't realised that quercetin has an effect on tamoxifen bioavailability.
 

Sherlock

Boswellia for lungs and MC stabllizing
Messages
1,287
Location
k8518704 USA
I take quercetin as a breast cancer prevention. I was advised by a nutrtional doctor to take it with bromelain before meals. I have also heard that vit C can help absorbtion of quercetin.

Interestingly I took tamoxifen for a while and hadn't realised that quercetin has an effect on tamoxifen bioavailability.
The first bottle I'd bought (Natrol brand) has vit C in it. I'm thinking to take my next bottle (Solaray, not with vt C) with something that naturally contains quercetin - like onions or citrus or tea. Maybe those things have substances that will help with absorbing the quercetin. However, I have the experience of taking 500 mg and seeing that my niacin flush was almost completely abolished - which seems to say that I am absorbing the quercetin. (I assume that Theoharides has worked out that quercetin is not blocking niacin absorption.)

Carol, do you have leaky gut and do you find that maybe bromelain makes that worse?
 

carolwxyz99

Senior Member
Messages
114
I have always had gut problems and have not associated the bromelain with leaky gut. But it may be worth me stopping it for a bit and restarting to see if I notice anything. I hadn't heard of bromelain causing leaky gut with quercetin before reading your posts, but I didn't really look hard.
 

jeffrez

Senior Member
Messages
1,112
Location
NY
I think what Little Bluestem said is accurate. Quercetin enhances bioavailability of certain substances by inhibiting the enzymes that break them down. That possibly could be dangerous in some situations, so be careful of what meds you're taking with it. :=)