I think the boost of energy you feel from an apple is more likely due to the sugar than to the quercetin.
There are many studies showing extension of life span in various organisms by quercetin. But this one SIRT1 stimulation by polyphenols is affected by their stability and metabolism says:We show that intracellular activity of SIRT1
in HT29 cells is only stimulated by resveratrol and not by
quercetin. This is probably due to rapid metabolism of quercetin because quercetin 3-O-glucuronide did not stimulate
recombinant SIRT1.
Another study claimed blocking of Sirt1 by quercetin-O-glucuronide.
The situation is not exactly clear. Life extension may have been due to other action of quercetin than sirt1. Interaction with resveratrol is also, as you said, not properly studied.
That would make sense, sans the apple skin is where quercetin is and not high amounts of sugar , and it still doesn't change that much greater energy/focus increase from raw quercetin at 500mg.
That was the paper I was referring too. I finally got my hands on it. The inhibition of their recombinant, in a test tube by itself with a fluorophor known to decrease substrate affinity (which is a huge biochemical no no when studying a protein), by the quercetin metabolite was slight. But when you put quercetin in with cells, that same study saw no inhibition of Sirt1. That study actually supports the idea that quercetin does not inhibit Sirt1. And again, their recombinant Sirt1 is flawed and I linked a study that showed that resveratrol too interacts with the fluorophor of that model system, not the Sirt1 directly, so that even the data about resveratrol binding is wrong and unacceptable when using that system. No conclusion is possible with it about the quercetin metabolite, and again, actual cells showed no inhibition (though they tried to pass off the no stimulation as the metabolite stoping quercetin from stimulating).
Hi geddarkstorm,
We also have seen the claim of the blocking of SIT1 by quercetin from an older study.
I figured in the most recent study using "Gene-ship" technology we would have seen an increase in SIRT1 with a resveratrol-quercetin mix, but I was surprised that there seemed to be the strong suggestion of the opposite happening. However it's not clear, and it is unknown that It may have been because of quercetin, or another item in the mixture. Consequently, it appears like marketing changed after this development.
Geddarkstorm, can you take a look and comment on the study regarding SIRT1?
http://www.sciencedi...1df3dccca811ec7
We continue to release resveratrol without quercetin, as the likelihood of inhibition of SIRT1 is a continued possibility.
A
I have seen that study, too. Apparently, the mixture, which is the bases of the longevinex formula, which also includes quercetin, activates the same genes as resveratrol and CR, and more. Again, this suggests quercetin does not inhibit Sirt1. They also had a ton of vitamin D in their mixture, so most of the gene changes that differed from raw resveratrol were probably due to that. Afterall, resveratrol synergizes with vitamin D by upregulating its receptor.
Edited by geddarkstorm, 20 December 2008 - 05:42 PM.