The metod proposed by Dr. Rogoza may work very well.

But, if your final scope is the extraction of rosmarinic acid, you may use a different approach which might avoid the simultaneous extraction of the essential oil components.

Rosmarinic acid is a water soluble substance, you may try to extract it with an acqueous solution of ethanol (20-25% of ethanol to avoid the microorganism contamination during the maceration and so fermentations).

In These conditions the solubilisation of the components of the essential oil might be avoided, so when you distillate the solution to recover the ethanol, the smell of rosemary should not be present.

You may try it firstly on a small quantity of plant materials and evaluate if this method could be useful for your purpose.

On the other hand you should also take in account that water is more difficult to evaporate in respect to ethanol (96%), and requires at least an higher temperature, also at reduced pressure. If you do not want to expose the extract to a temperature higher than 45° C when you're eliminating the extraction solvent.

However, the concentration of the extract may be stopped when all the ethanol has been evaporated and the extract is an acqueous suspension. This suspension may be frozen and then lyophilized

If you plan to try this method, then let us know what were the results.

During the distillation the essential oil is distillated together with ethanol.

You may try to add some activated charcoal to the distillate and then filter the solution.

The components of the oil might be adsorbed on the charcoal leaving the ethanol odour free.

Proven way :

Dilute alcohol with water, add paraffine (liquid or molten), mix well, separate water layer. Repeat if it needed. Activated charcoal is also good in final purification, but more complex. Distill water layer  to obtain pure alcohol; water is recycled. In vacuum at high temperature you can regenerate paraffine.

The metod proposed by Dr. Rogoza may work very well.

But, if your final scope is the extraction of rosmarinic acid, you may use a different approach which might avoid the simultaneous extraction of the essential oil components.

Rosmarinic acid is a water soluble substance, you may try to extract it with an acqueous solution of ethanol (20-25% of ethanol to avoid the microorganism contamination during the maceration and so fermentations).

In These conditions the solubilisation of the components of the essential oil might be avoided, so when you distillate the solution to recover the ethanol, the smell of rosemary should not be present.

You may try it firstly on a small quantity of plant materials and evaluate if this method could be useful for your purpose.

On the other hand you should also take in account that water is more difficult to evaporate in respect to ethanol (96%), and requires at least an higher temperature, also at reduced pressure. If you do not want to expose the extract to a temperature higher than 45° C when you're eliminating the extraction solvent.

However, the concentration of the extract may be stopped when all the ethanol has been evaporated and the extract is an acqueous suspension. This suspension may be frozen and then lyophilized

If you plan to try this method, then let us know what were the results.

Problem with method suggested by Alessandro (20-25% aq EtOH) is extraction of odoriferous eucalyptol (1,3,3-trimethyl-2-oxabicyclo[2,2,2]octane, cineol, cineole) and borneol . The last is slightly soluble in water without EtOH and very soluble in 20-25% aq EtOH.

Dr. Rogoza maybe he's right, I've not checked the solubility of these substances, but in cases like these, when you do an extraction from a complex matrix is virtually impossible to extract a single component. If it were possible to extract using just water without incurring in a possible contamination by micro-organisms I would have suggested. In fact, a percentage of 20-25% ethanol would be sufficient to prevent the development of microorganisms that could degrade the quality of the extract. In addition, in this way, one should employ a reduced amount of ethanol compared to the original method of extraction.

Dear Dr. Vendetti, 20-25% ethanol is non-effective as bactericide. Most effective is 70% EtOH in water (Spiritus aethylicus 70% , also known as "medicinal alcohol") . But even in such a concentration, 70% aq alcohol is not sporocide. http://en.wikipedia.org/wiki/Disinfectant

GOOGLE IN HELP! ;-)

It does not need to kill any microorganisms eventually present.

The 20-25 % of acqueous ethanol is bacteriostatic/fungistatic, and this is a sufficient condition to prevent the development of these microorganisms.

As reported in: Victor Lorian [Editor], Antibiotics in Laboratory Medicine, Lippincott Williams & Wilkins, Philadelphia, USA, 2005, page 625

"Ethanol is bacteriostatic and inhibits spore germination at concentration around 10% (v/v), is bactericida at ≥ 30% (v/v), but loses its activity at ≥ 90 % (v/v), indicating the need for water for biocidal activity”

IMHO, deep misunderstanding of real problem is presented. Replacement of good solvent (EtOH) for rosmarinic acid by bad solvent (20% aq EtOH), in hope to suppress ( not kill) mythic bacteria. In reality - components of rosemary oil are more active as bactericide in times by order as compared with 20% aq EtOH. http://www.aromaticplantproject.com/articles_archive/Rosemary_OilProfile.html

Google is impotent in such heavy case....Woodoo science....

Virtually all essential oils have antibacterial activity. But the opening speech was another.

That is how to extract rosmarinic acid without simultaneously extract the non-polar component, and not on how to make sterile or stabilize in terms of microbial any solution. Also I was given to understand that those who place the original question wanted to avoid or limit the extraction of oil components.

Dear Dr Ouhsaine, you're welcome.

I'm sorry that the method does not satisfy your expectative, but, it should be taken in account that all the operations conducted on an extract may introduce artefacts. Treatment with charcoal is not free from this type of problem. In fact many aromatic substances were present in traces in activated charcoal. Also the sterilization at 120° C may introduce artifacts which originate odour substances.