Sciencemadness Discussion Board - Menthol extraction from peppermint

Menthol extraction from peppermint

Kamikaza - 13-7-2011 at 08:04

The last few days I have been trying to extract menthol from peppermint. Yesterday the experiment finally succeeded, but it was terribly inefficient. Out of the 100 grams peppermint, I only got two very small crystals of menthol. The peppermint is made up mostly of sugar and a little bit of menthol. Here are the methods I tried:

1. Dissolving peppermint in water, seperation with kerosene. No yield.
2. Dissolving peppermint in alchohol. No yield.
3. Dissolving peppermint in water, seperation with acetone with slight shaking. No yield.
4. Dissolving peppermint in acetone. Very little yield.

I tried to extract with chloroform, as that would have the best chance, but I couldn't get enough made with the acetone + NaClO reaction. If any of you have ideas for better methods, please share.

These are the solvents I have: water, kerosene (lamp oil), acetone, alchohol.

Waffles SS - 13-7-2011 at 09:10

First you should dry peppermint Leaf then add enough acetone and filter solution then cool fast your solution(below 10c)
menthol will crystall out.
Dried peppermint typically has 0.3-0.4% of volatile oil containing menthol (29-48%), menthone (20-31%), menthyl acetate (3-10%), menthofuran (1-7%) and many trace consituents including limonene, pulegone, eucalyptol, and pinene

[Edited on 13-7-2011 by Waffles SS]

fledarmus - 13-7-2011 at 09:25

Quote: Originally posted by Kamikaza

. The peppermint is made up mostly of sugar and a little bit of menthol.

Are you starting from peppermint candy? Or the plant peppermint?

Kamikaza - 13-7-2011 at 09:59

I tried it one time with wild peppermint (this produced nothing), and one time with peppermint candy, this produced the tiny cristals. I thought that the candy would have the highest concentration, but I could be wrong.

Kamikaza - 13-7-2011 at 10:02

Quote: Originally posted by Kamikaza

add enough acetone and filter solution then cool fast your solution(below 10c)
menthol will crystall out.

I'll try this. Where would I most likely find dried peppermint leafes? And is it possible to seperate the mentol from the menthone, mentonacetate and mentofuran by recristallisation?

[Edited on 13-7-2011 by Kamikaza]

fledarmus - 13-7-2011 at 10:17

Peppermint candy has very little peppermint in it - my recipe uses 1/2 teaspoon (~2.5mL) peppermint extract in 1 cup (~240mL) sugar. Note, that's peppermint extract (mostly alcohol), not peppermint oil. I'm impressed you were able to isolate anything from 100gm of peppermint candy.

Peppermint oil and peppermint extract are both readily available and cheap - they would probably make better starting points if you don't have access to large amounts of peppermint leaves. If you've got a little time, though, peppermint grows like a weed (which it is!) and if you plant some now, you'll have more than you know what to do with by next year at this time.

Kamikaza - 14-7-2011 at 11:09

Well, today I bought around 20 grams of chopped up, dried mint leaves. I bathed it in 185 ml of acetone, and boiled it. After filtering I recovered around 85 ml of acetone (100 ml stayed in the leaves and filter paper

). I put this in the fridge, and let it cool for 10 minutes. It was sufficiently cooled, but nothing crystallised. I eveporated around 40 ml of acetone of that mix, and let it cool for 10 minutes again. Again nothing crystallised.

Then I eveporated the rest of the acetone and recovered a green sludge. This definitely smelled like menthol, and it tasted like super strong chewing gum (I tasted it by touching it with the tip of my tong), so it must contain concentrated menthol

. The question however is how I should purify it from the rest of the sludge? My first thought was recrystallisation, but which solvent should I use?

Rich_Insane - 14-7-2011 at 14:36

Menthol is largely insoluble in water. I would reccomend first doing some good drying and grinding. It will make your extract very sludgy, but it's worth it. Suspend this in naptha, chloroform or an alcohol (2-propanol or ethanol). Filter the remainder out via coffee filter but not before vigorous stirring and 2-24 hours of sitting to allow everything to come out. Most of the sugars/chlorophyll/cellulose will remain in the sludge, which you can wash with alcohol or naphtha to get any remaining menthol. The resulting naptha/solvent will contain menthol as well as lipids and assorted cellular gunk. You can evaporate this to a tar of some sort and wash it with cold water briefly. Maybe adding alcohol and filtering might get you more of the menthol. You could then recrystallize in water or simply evaporate and scrape off the crystals.

I did dry peppermint once. I left it in a jar and let it sit in the sun for a week. A dessicating agent might suck up the final bits of water. It should smell mildly citrus as well as minty due to other terpenes in the dried plant matter.

[Edited on 14-7-2011 by Rich_Insane]

I recommend ...

The WiZard is In - 14-7-2011 at 16:33

growing you own...

for other sources

www.justfuckinggoogleit.com

Mentioned in passing — US Patent 2 760 993

Separation of methanol from mint oils by chromatographic absorption

Morgan - 14-7-2011 at 18:37

I recall driving in the countryside through a somewhat vast field of mint on either side of a road when I lived in Oregon. You could really smell the mint. ha

[Edited on 15-7-2011 by Morgan]

Waffles SS - 15-7-2011 at 00:11

Quote: Originally posted by Rich_Insane

Menthol is largely insoluble in water. I would reccomend first doing some good drying and grinding. It will make your extract very sludgy, but it's worth it. Suspend this in naptha, chloroform or an alcohol (2-propanol or ethanol). Filter the remainder out via coffee filter but not before vigorous stirring and 2-24 hours of sitting to allow everything to come out. Most of the sugars/chlorophyll/cellulose will remain in the sludge, which you can wash with alcohol or naphtha to get any remaining menthol. The resulting naptha/solvent will contain menthol as well as lipids and assorted cellular gunk. You can evaporate this to a tar of some sort and wash it with cold water briefly. Maybe adding alcohol and filtering might get you more of the menthol. You could then recrystallize in water or simply evaporate and scrape off the crystals.

I did dry peppermint once. I left it in a jar and let it sit in the sun for a week. A dessicating agent might suck up the final bits of water. It should smell mildly citrus as well as minty due to other terpenes in the dried plant matter.

[Edited on 14-7-2011 by Rich_Insane]

By this method you will have a mixture of menthol,menthone,menthyl acetate,menthofuran,..
Fast cooling is useable method for separation L(-)menthol from peppermint oil.For this purpose you should provide Supersaturated solution of peppermint oil and solvent(ethanol or acetone or..)
@Kamikaza ,
Try to study The Chemistry of Essential Oils and Artificial Perfumes Volume I(and II) in Library:
http://library.sciencemadness.org/library/index.html

[Edited on 15-7-2011 by Waffles SS]