Herbs as reducing agents? and HAuCl4 vs solid gold?

[LionHeart]

I've read an article about using herbal extracts to make colloidal gold from HAuCl4.

Have anyone tried this?

And what is the difference between making colloidal gold from HAuCl4 vs the electrolysis process?

I've seen the recipe in this forum for making colloidal gold with cinnamon extract. The cinnamon can be used as a reducing agent, so my question is if it's necessary to also add citrate in to the mix?

[kephra]

Lots of things can be used, but herbals have a lot of stuff that is not useful.  You will get a purer product without using them.

Making colloidal gold from gold chloride is extremely simple, needs no equipment, and produces the purest product. Its a lot more complicated doing electrolysis with gold metal. 

As to cinnamon and citrate, the citrate is probably not necessary.  But why bother with cinnamon when its much easier and better to use maltodextrin or even corn syrup?

[LionHeart]

Do you think there could be any stuff in the herbs that could interfere with the electrolysis?

I'm under the impression that many use electrolysis, but using gold chloride seem to have many advantages. Is it because it's cheaper or are there any other good reasons to use electrolysis?

I'm interested in using herbs, because colloidal gold could also help make some polyphenols more biocompatible by increasing bioavailability. I know this is a growing area where a lot of research is being made.

[kephra]

The only advantage to electrolysis is that its easier in most countries to get gold metal than gold chloride.  The product isn't quite as good but once you own the equipment and the gold, its cheaper.

If you want to mix C G wiyh herbals, it would be better to make the colloidal gold with corn syrup first, then add the herbals.

[LionHeart]

Ok, but if I use corn syrup as reducing agent before adding the herb, will the gold particles be bound to the reducing agents in the herb?

Btw, can you explain the difference between a reducing and a capping agent?

[kephra]

You need to read the articles.

A reducing agent donates electrons to the metal ions converting them to metallic particles.  In doing so, the reducing agent becomes oxidized.  So using herbs may reduce gold, but in the process the usefulness of the herb will likely be destroyed.  This is why I said it would be better to reduce with corn syrup first, which isn't a very strong capping agent, then add the herbs.  I spend a lot of time reading research papers about silver and gold, and I have yet to find any in-vivo studies that featured herbal coated gold nanoparticles.

A capping agent surrounds the resulting metallic particles keeping them from touching and growing into bigger particles.

Some substances are both, and some are stronger than others. 

It may not be possible to do what you want to do.  Do you have any real research that details how?  Ionic gold is very toxic, so you want to be sure you don't have any in the finished product. 

[LionHeart]

My understanding is that the polyphenols reduce gold chloride into metallic particles by conjugating with the gold, a complex which can serve as a delivery system to get the polyphenols into tissues without being broken down on the way, so their usefulness do not necessarily get destroyed, maybe on the contrary.

Try and read this: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4211914/, this is made on isolated polyphenols though, but the same should be possible with a herbal extract.

I also find this one interesting: http://www.sciencedirect.com/science/article/pii/S1359511311002510, where they show that colloidal gold reduced with ginger is more stable in physiological conditions than colloidal gold reduced with citrate.

So a capping agent is basically the same as a stabilizing agent? and you don't think it's possible to conjugate the gold with polyphenols after you have reduced it with syrup first?

[kephra]

Thanks for the links.  There is not much new there though. 
For instance, using ginger is the same concept as using cinnamon.  Any food substance which is noted as a good antioxidant should work, as an antioxidant is a reducing agent.  Even tea will reduce gold. 

But so far, there is no real evidence that this does any good in-vivo. 

Lets consider a solution containing 10 mg of gold.  For the reduction, three molecules of a reducing agent will be required, and lets assume that polyphenols have a molecular weight of 4000 compared to gold at roughly 200.  From this, it would appear that 0.6 grams of polyphenol would be required to reduce the gold resulting in .6 grams of oxidized polyphenols. 
At this point you would have nanoparticles of 10 to 20 nm in diameter.  Now, the oxidized polyphenols would have coated the nanoparticles, but far less is required, since only the surface atoms can be attached to the polyphenols.  Most of the polyphenols are now free in the solution.  In this size range, less than 10% of the gold atoms are surface atoms, so we can say that 90% of the polyphenols will not be attached to the gold.  So we have 60 milligrams of phenols on the gold, and 540 mg of oxidized phenols loose in the solution. 

What would happen when consumed?  I think its most likely that the digestive process will strip off the polyphenols, and the naked gold will be absorbed separately from the polyphenols.  The polyphenols will also be absorbed, and they will be reduced by glutathione which is the bodies strongest reducing agent if at all.  If they are reduced, they waste the bodies glutathione, and if not they are no longer antioxidants.

If these gold-phenol particles were to have beneficial affects beyond what gold alone has, they would have to be injected to bypass the digestive system, and the gold would have had to be reduced by some other means first.

So until there is actual in-vivo evidence showing that orally consumed herbal reduced gold nanoparticles has real benefits, I would not bother.  But I encourage you to experiment..  I see no real harm in it either.

Edited by Kephra

[LionHeart]

Thanks a lot. That's some great points you make.

I came across this paper http://www.ncbi.nlm.nih.gov/pubmed/16378435/, where they show that oral administration of colloidal gold-insulin reduced blood sugar levels in vivo, as opposed to unbound insulin.

"Oral administration of insulin solution (curve 1, Figure 3B) did not result in a detectable reduction in blood glucose levels even after 5 h of dosage, which is mainly attributed to poor uptake and enzymatic degradation of insulin in the gastrointestinal tract. However, oral administration
of both formulation A, Au-Ins (curve 4, Figure 3B) and formulation B, Au-Asp-Ins (curve 5, Figure 3B) resulted in a detectable reduction in blood glucose levels of up to 19 and 31%, respectively. This result indicates that in both cases the gold-nanoparticle-surface-bound insulin is bioactive and that the absorption of insulin is enhanced in the formulation where insulin is bound to the amino acid-modified nanogold surface."

Maybe something similar could be the case with colloidal gold-phenols? Haven't seen it yet, but this shows that the GI-tract doesn't cut things off the colloidal gold per se.

What do you think of their preparation of colloidal gold-insulin? Could it be possible with polyphenols as well? First making the colloids, using syrup or citrate, and then removing those agents from the surface and replace them with polyphenols. That could be a way to avoid oxidized forms of polyphenols.

[kephra]

What do you think of their preparation of colloidal gold-insulin? Could it be possible with polyphenols as well? First making the colloids, using syrup or citrate, and then removing those agents from the surface and replace them with polyphenols. That could be a way to avoid oxidized forms of polyphenols.

In the paper you referenced, the gold that was effective was delivered nasally, not orally.  It bypassed the digestive system.

Our principle observations are that there is a significant reduction of blood glucose levels (postprandial hyperglycemia) when insulin is delivered using gold nanoparticles as carriers by the transmucosal route in diabetic rats. Furthermore, control of postprandial hyperglycemia by the intranasal delivery protocol is comparable to that achieved using the standard subcutaneous administration used for type I diabetes mellitus, thus showing considerable promise for further development.

And in this paper http://www.jnanobiotechnology.com/content/8/1/16,  it appears that gold alone has an effect on blood glucose, but look at the dosage required!

[LionHeart]

They also saw a reduction in blood glucose with the oral administration of colloidal gold-insulin, as it says in the quote I added in my previous post. You can see the figures in the paper. They use colloidal gold as a control but I can't figure out the dosage, I can just see they use 1ml. But the colloidal gold-insulin lowers glucose levels significantly more than colloidal gold by itself (however, dosage may be a confounding factor here, can you see the actual amount of gold in the colloidal gold group?). The dosages of the colloidal gold-insulin (2,25mg/kg) is practically the same as in the colloidal gold dosage (2,5mg/kg) in the article you posted (however the insulin also account for some of the weight though). I find it difficult to compare the effects on blood sugar levels, as they use different units and different groups.

But do you think that it is possible to remove the reducing agent on the surface after colloidal gold is made and replace it with a polyphenol? In a relatively simple way?

[kephra]

Yeah, these things are difficult and sometime purposely obfuscated.
I did manage to obtain the complete paper, and one thing to point out is that although the oral and nasal curves for gold-insulin look about the same, the insulin dose for oral was 5 time the nasal dose.

It is still very interesting though, and offers promise.

[LionHeart]

Yes, I also believe that it offers promise. But I can see as you have pointed out that the digestive system can be a difficult thing to overcome, but the research is hammering away, so maybe we'll know more soon. To be fair the oral dosage was "only" 2,5x the amount of nasal group, but that's still a pretty significant difference. Maybe using a nasal spray instead of drinking it would be a better route.

[kephra]

To be fair the oral dosage was "only" 2,5x the amount of nasal group, but that's still a pretty significant difference.

Figure 9:

Fig. 9. Percent reduction in blood glucose level after oral adminis- tration of a insulin loaded chitosan reduced gold nanoparticles, b blank chitosan reduced nanoparticles, c insulin solution, d insulin in chitosan solution (Dose 50 IU/Kg, n = 6).

Figure 10:

Fig. 10. Percent reduction in blood glucose level after nasal administration of a insulin loaded chitosan reduced gold nano- particles, b blank chitosan reduced nanoparticles, c insulin solution, d insulin in chitosan solution (Dose 10 IU/Kg, n = 6).

Unless we are reading a different paper, the graphs show a 5 to 1 ratio.

[LionHeart]

I think we are reading different paper. The one I'm referring to is this one:

Langmuir. 2006 Jan 3;22(1):300-5.
Gold nanoparticles as carriers for efficient transmucosal insulin delivery.
Joshi HM1, Bhumkar DR, Joshi K, Pokharkar V, Sastry M.

Unfortunately I'm not able to attach the pdf, but hope you can find it.

Which one are you referring to?