Improved freezing of Asarone from Calamus oil

[nautilus]

Dear bees, this is my first real contribution. Hope you like it.

In short: It's much easier to get good asarone crystals from your Indian calamus oil if you add a little ethanol!

The long version: after I tried my first freezing experiment, I scooped a spoonful out of the container, after decanting the low-boiling stuff as much as possible, after melting a bit. Then I cleaned the crystals in a coffee filter with ice-cold 100% ethanol. It's important to note that the entire contents of the beaker were frozen, even though there were color-differences in the mass.

This is what it looked like before the thawing and scooping:


(note: the paper underneath is not pure white but a very light beige/yellow)

At the time I wasn't convinced that what I got was actually pure, so I let the the now cleaned crystals melt and put the beaker back in the fridge. Only now there was a bit of ethanol mixed in of course, from the washing, which I intend to distill off later.

The crystals formed again, only much slower (two days before they started to form), and this time a fraction of the beaker's contents stayed liquid, like this:



Important: the crystal mass formed in about two days, and the liquid on top has not decreased further in the two days after that. It's stable.

I hypothesised that the EtOH is preventing the non-Asarone from crystallizing, while the Asarone itself is not affected because it is relatively apolar (I think. Please note: I'm much more a cook than a chemist at this time).

So I tried mixing in a dash (a few milliliters) of EtOH with a larger volume of the oil, and this is what it looks like right now (after two days in the fridge):



Beautiful huge crystals! And they're still growing! In fact, it looks like a mono-crystal of about an inch across.

I have not taken the experiment further yet, so I am not sure (and have no other way to confirm than boiling point and density) if this is in fact the asarone fraction, but since it is by far the largest fraction, I'm pretty sure that it is.
If you recognize the color, shape or other attributes to confirm or deny this, please let me know!

Since it's pretty hot right now where I live, it's not really an option to start fiddling with the fridge temperature. I think this new way might make things a bit easier for the bees among us working with asarone. Let me know if you can repeat this finding, hopefully it works with other batches of oil as well.

Hope this helps!
nautilus

EDIT: PS: Before this I tried the freezing and thawing procedure as described elsewhere on this forum, waiting for a layer to form, but that didn't work for me.

[Rasputin]

I just got a gallon of Indian Calamus Oil a week ago. I was wondering if it could be frozen out like Safrole. A liter of it is already in the freezer, I cant wait to see what freezes out. I truly hope it is this easy, because if it is, then these are truly exiting times to live in(MDMA and MDA are just to hard to pull off nowadays, but TMA-2 on the other hand is an awesome substance in my opinion, with pretty easy reagents to aquire), the wave of the future is TMA-2. Well at least in my part of the country, after all "Rolls" are really getting scarce. Many people I know and myself have tried TMA-2, and we all liked it very much. It could very well be the "Next big thing". Oh yeah at what temp(if you happen to recall) did your Asarone freeze out.

Thanks Nautilus: For paving the way.

[Osmium]

The asarone isomer which is the main component of Indian Calamus oil (ß-asarone) does not solidify at freezer temperatures.
alpha-asarone has a MP of about 65°C if I remember correctly. But there's only a few percent at best in Indian Calamus oil, and you definitely won't be able to separate it by freezing.

[armageddon]

you definitely won't be able to separate it by freezing

well, obviously at least something separated upon freezing...


And if it is alpha-asarone, then the solids should be discarded - the remaining liquid should give pure beta-asarone upon distillation....

(still a nice crude separation method - as long as the crystals in above pictures aren't just plain H2O..)

Just out of pure curiosity: what do you think the solids are, Os? I don't think it is a-asarone, as indian calmus doesn't contain that much that it would result in such a massive amount of crystals - one of the pics shows a beaker filled with white solids with no yellow liquid being visible anymore. And I therefore doubt that the solids are a-asarone - the proportion crystals/liquid simply doesn't match with the asarone content of the essentil oil.

Greetz A

[Osmium]

The oil certainly isn't indian calamus as I know it. Impossible to say without a GC analysis what it really is and where it came from.

There are other varieties of asarone containing oils, e.g. from Europe, that can have considerable asarone and elemicin etc. content in the 30-50% region, but their composition varies a lot, they are restricted to certain locations and I don't think that they are produced in considerable amounts. They also would be rather expensive.

[nautilus]

Well, on the bottle it says 'Calamus root, Acorus calamus, India, Steam distilled essential oil'. I paid about US$ 30 for 450 ml.

Update: I thawed and re-froze the little beaker with the small amount of washed white crystals. The crystals formed again, now almost a pure white, and there is a small film of oil on top again. It's paler in color and smaller than before. So whatever it is I'm extracting, at least it's getting purer  

I also put the beaker from the last photo in the fridge again. Appararently moving it about was not a good idea, because the rest of the stuff froze up completely again in a darker mass of small crystals that trap the residu inside.

Right now I'm thawing it again, I'll add a bit more ethanol to it and re-freeze. I'll report back with the results soon.

Thanks for working with me guys,
nautilus

[Rhodium]

I'm not 100% sure (notes not handy at the moment), but I think I have crystallized pure distilled beta-asarone at freezer temperatures. I cannot find any precise melting points in the literature though.

[Stalin]

The oil certainly isn't indian calamus as I know it. Impossible to say without a GC analysis what it really is and where it came from.

There are other varieties of asarone containing oils, e.g. from Europe, that can have considerable asarone and elemicin etc. content in the 30-50% region, but their composition varies a lot, they are restricted to certain locations and I don't think that they are produced in considerable amounts. They also would be rather expensive.

Calamus oil is (or should be) derived from Acorus calamus, also known as sweet flag. This plant grows in many part of the Northern hemisphere. They usually divide the plant into three subtypes, namely American, European and Indian calamus. They are all three different genotypes, which causes a variation in their essential oil content. The essential oil of American sweet flag contains only traces of asarones, while European sweet flag oil has a whopping 5% (at most). The oil derived from the Indian sweet flag contains somewhere between 70 and 90% asarones.

European calamus oil is approved for use in pharmaceutical preparations due to its low asarone content. As you might or might not know, asarone is a carcinogenic substance. Hence, Indian calamus oil is banned for pharmaceutical applications in Europe. In India, however, calamus oil is used as a medicine.

Aside A calamus, asarone containing essential oils may also be derived from various Asarum species. I think the European chemists from the 19th century isolated asarone by steam distilling Asarum europaeum, and in China and Korea, Asarum sieboldii is commercially grown for its essential oil. I'm not sure how much asarones it exactly contains, but I thought it was somewhere near 50%. Even though its essential oil is available worldwide, it is much more expensive than Indian calamus oil.

[starlight]

If you isomerise the oil by heating with KOH, you should get more of the trans isomer that has a higher melting point. That could help in crystallization

[nautilus]

Update: Sadly I've not been able to reproduce my earlier results. I've tried smaller containers (to prevent crystals from growing too big) and lower temperatures (make them grow slower). To no avail: for some reason the stuff has decided to start freezing completely again.

Next I'll try starlight's tip, isomerization by heating with KOH.

Two questions though:
1. it's likely that at least some KOH will dissolve (because of water content, or otherwise), so I suppose an extraction will be in order. Which solvent do you bees recommend?
2. How much KOH should I use per mole, volume or weight of the oil, approximately?

Thanks in advance!

[starlight]

With regards to isomerizing with KOH, you could follow the quantities/methods used for isomerization of Safrole on Rhodium's page.  Experimentation will be necessary in order to determine the time required for most of the asarone to become the trans isomer.

With regard to the KOH, recrystallization will remove this if any remains dissolved post-reflux.

Have a look at:

https://www.thevespiary.org/rhodium/Rhodium/chemistry/isomerizafrole.html

One more thing, I am not sure whether cis to trans conversion is as rapid with ethanolic KOH as with KOH in neat oil.

This is a technique that needs to be experimented with in order to assess its utility.