Extracting Active Ingredient from Stevia Leaf

[jmnew51]

I've scoured the net looking for some ideas on how to extract the active ingredient from the stevia leaf.

A while back my brother (a health nut) had some of this white powdered stevia extract, that was dynamite. You only needed a pinch to sweeten a whole cup of coffee.

We have a lot of the green powdered leaf and can do a water extract, but have no clue as to how to separate the gunk and clorophyll out of it prior to reducing it through evaporation.

I tried a solvent wash on a small sample and nothing was extracted into the solvent.

I was wondering if there was some process of extracting the glucoside steviol into some other solvent, but I would think that you would still have to get rid of the gunk first as most solvents aren't as selective as you would like.

Just that we have a lot of this green stevia powder laying around and I would like to find a use for it. I don't like using it the way it is. :yuck:

Thanx

JIm

 

[chemisttree]

Traditionally, this has been accomplished by extraction of the stevioside and the rebaudioside into methanol, ethanol or n-propyl or isopropyl alcohol. The alcoholate solutions are evaporated onto chromatographic silica and various solvents from low to high polarity are passed over a column of this material to obtain fractions of varying purity. Alternatively, water can be used to extract the glycosolyated steviols and the resulting extract solution treated with calcium hydroxide. The filtered solution is then passed through strongly acidic ion exchange media (Dowex 50W) and through weakly basic ion exchange media (Dowex WGR). The process can be repeated as many as 5 times to obtain the purified, colorless extract. The extract is evaporated to a powder using a spray dryer. If you evaporate it to dryness (hard) using a shallow pan, you will have to scrape it off the bottom of the pan (pain!) and grind it.

 

[jmnew51]

Thanx for the info.

I did think that the water extract would be a little more work than anticipated. Just I don't have my hands on any methanol of sufficient purity at the moment, only 99%, industrial grade.

When I get my hands on some better grade alcohol, I will then try the chromatographic process.

BTW thinking of 99% methanol. how could I make nearly anhydrous methanol?

Would passing through silica gel work? Or would the gel absorb the alcohol also. I know of one preferred dessicant, but can't think of the name.

I am planning on making biodeisel in the near future, and anydrous methanol is extremely expensive to use on a scale that large.

Thanx again

Jim

 

[chemisttree]

99% is nearly anhydrous and is good enough for biodiesel.

 

[jmnew51]

I thought so, but I heard that the methanol and the sodium hydroxide should be completely dry.
I know that MEOH is extremely hygroscopic(as is NaOH) and after continually opening and coling the container who knows what the percentage would be after some time.

Thanx

Jim

 

[chemisttree]

Its always best if the methanol and sodium hydroxide are absolutely dry but when you are making biodiesel from used oil, the concentration of contaminants in the oil largely outweigh any gain you would see by using absolutely pure methanol and NaOH. It is best to try the transesterification on a small sample to determine if your ingredients are suitable. It is pretty simple and only takes about an hour. Search the 'Journey to Forever' website for the method.

 

[jmnew51]

Hey! I read that journey to forever site quite extensively.

Thanx again.

JIm