if you are concentrating in thermolabile substance than you have to go cold extraction method other wise you can go for hot extraction method (Soxhlet)

There is no answer which is valid in any case. It depends on the structure of the compound you want to extract and on the "difference" of its solubility properties in comparison to the solubility properties of all other compounds present in the raw material. To think about this difference and in the same way to think about a suitable solvent that would preferably dissolve the desired compound is the key to the answer to the question if Soxhlet extraction may be suitable or not. It should also kept in mind, that Soxhlet extraction does occur at "ca. room temperature" because the solvent that is dropping into the Soxhlet thimble comes from the lower part of a reflux condenser, that means it is not a hot solvent.

If you are not sure, have a try! But try to think deep enough about the "combination" of compound to isolate and suitable solvent for this.

From Wikipedia: "Normally a solid material containing some of the desired compound is placed inside a thimble made from thick filter paper, which is loaded into the main chamber of the Soxhlet extractor. The extraction solvent to be used is taken into a distillation flask and the Soxhlet extractor is now placed onto this flask. The Soxhlet is then equipped with a condenser.

The solvent is heated to reflux. The solvent vapour travels up a distillation arm, and floods into the chamber housing the thimble of solid. The condenser ensures that any solvent vapour cools, and drips back down into the chamber housing the solid material.

The chamber containing the solid material is slowly filled with warm solvent. Some of the desired compound will then dissolve in the warm solvent. When the Soxhlet chamber is almost full, the chamber is automatically emptied by a siphon side arm, with the solvent running back down to the distillation flask. The thimble ensures that the rapid motion of the solvent does not transport any solid material to the still pot. This cycle may be allowed to repeat many times, over hours or days."

This shows that the desired compounds will be stored in the solvent for long time at boiling temperature. If the compounds are heat stable (at the boiling temperature of the solvent) this is ok. If not, degradation may occur and you will have different compounds in the solvent than in the plant material.

However, for total extraction (repeating of the cycles) Soxhlet extraction is the best method.

You may roughly test the situation by TLC of a Soxhlet extraction versus a liquid extraction at ambient temperature.

This is all absolutely fine and correct. The only thing that - besides heat stability and solubility in the thimble - should be kept in mind is an ideally big difference in the solubility of the wanted compound in comparison to unwanted side components, that in the preferred case, should not at all or not good dissolve in the solvent.

To find this is a procedure both of rationality and experience. In any case of uncertainty a trial is recommendable.

Many substances have antimicrobial activity. I think the method of isolation in this case should not affect the antimicrobial properties of your substances. Generally, the extraction method using a Soxhlet apparatus is one of the best methods for extraction

Solid-liquid and liquid-liquid extraction remains the better option for extractive bio-active components over Soxhlet extraction! It is belief that the pouring of condensed solvent onto the extraction material (i.e. the plant leave) may have a negative effect on the confirmation of the compound of interest (in your case the antimicrobial components)!

Hope this helps!

Thank you for your question. In order to be sure which of the three methods is the best ; why don't you try the three of them once on the same weight of the plant using the same solvent? The yield of three extracts will let you know which is the best.

I always use solid liquid extraction followed by liquid-liquid extraction. So far I am satisfied with this combination. I never use Soxhlet, but I think you have to consider if the high temperature will not affect thermaloble compounds in your extract. Other problem is when you have to continue with large scale extraction. I dont know if it is possible to use Soxhlet to extract for example 1 kg of dry plant material? While with solid liquid method it is not a problem at all. Hope this helps. good luck!

Extraction method (hot or cold), solvent used (non polar, polar, mixture), duration etc can substantially affect the chemical composition and yield of crude extracts especially oils and thus biological activity. If you want to test the fractionated extracts for antimicrobial activity, then you may use either of the methods. However, if you wish to isolate, characterize and screen for biological activity, i would suggest you to go for soxhlet extraction due to ease of operation.

Dear Camille Laluces

If you want to isolate the antimicrobial compounds from plants. it is always preferred the sequential extraction. after the sequential extraction you can check the antimicrobial activity and choose the active extract and go for the chromatography techniques. The sequential extraction (non polar to polar solvents) can be done using all of the mentioned methods. but I prefer the soxlet's extraction method. Because this method can be used to extract all of the solvent soluble compounds (it never left even trace amount of solvent soluble compounds) in the plant powder. after one extraction, you need to dry the plant powder until all the solvents to be removed and then again load the dried plant powder and start extraction procedure using next solvent. likewise you can sequentially extract up-to ethanol. Finally the water extract can be done using solid-liquid extraction.

Liqiud-liquid and solid-liquid extraction will be helpful during the compound purification.

The only disadvantage is you can't use this method for heat labile compound's isolation,

It depends on the structure, nature and solubility of compound present in the sample. Although solvent extraction play a role as best method due to siphning process for extraction of chemical compounds from plant material....................

Dear Camille Laluces

Soxhlet extraction by means of me is good but is better and more effective than extraction method solid-liquid and liquid-liquid antimicrobial components to isolate the various anatomical parts of the plants. Of course , there is never a 100 % certainty , you always need to take into account the relationship by which we mean that the group of substances , and its solubility in the solvent , which we choose . It is mainly the extraction of active substances , which are contained in the plant material , regardless whether they have purely antibacterial , antifungal or another . There is no clear answer to this question.

It also depends on what material we attempt , whether it is 2g or 1kg .

I prefer and mostly I use extraction method using Soxleta . Because this method can be used to extract the active ingredients any solvent in the raw material plant .

Dear Agnieszka Najda

I agree with your answer

Hi!

You need to search literature or compare different extraction methods to answer your question,

best regards Patrícia Rijo

Yes, but in the literature there is no answer to the question that this method is better or worse. search on various raw materials of extracted from different ways, you can only comparatively assess the results were the authors of the plant or plant material. And remember that each of them will behave differently.

Temperature is one of the most important factors, but extraction can be carried out cold , like it used long ago by percolation of raw ekstrachentem , but if it's not those times . Let us remember that some substances may be only when the sample were extracted heat up .

Rajaram Krishnasamy ·

thank you for your support of my thesis.

Depend from the chemical nature of the target components. When they are thermostable, then the Soxhlet method is suitable (as the operation temperature is the boiling temperature of the solvent and the duration is several hours, the possibility oft thermal decompostion is high). A much better method are the pressurized liquid extraction. In this case, the temperature is higher, but the duration is only several minutes. When the antimicrobials are volatile compounds, the hydrodistillation methods are recommanded (in classic, or microwave heated Clevenger apparatus). But the best method is the supercritical fluid extraction using pure CO2 or CO2+ethanol as solvent. In this case the selectivity is much higher and the solvent selectivity is tunable by changing the process parameters (temperature and pressure).

I would suggest to use the innovative RSLDE (Rapid Solid-Liquid Dynamic Extraction) that is performed by Naviglio Extractor. This technique is suitable for thermolable compounds and water cold water can be used for solid-liquid extraction to isolate antimicrobial components from leaves. Please see literature on my profile.

For solid samples , soxhlet extraction method is better than LLE even though it is time consuming.

There is no method that is superior. If Soxhlet extraction is a good choice or not depends mainly on the structure and thermal stability of the compound. Soxhlet extraction is sometimes VERY selective, and then THIS is the advantage in comparison to others. Generally, in chemistry it is the EXPERIMENT that makes the decision. Generally, one has to work more than is expected or desired. A definite advanate of Soxhlet ext is that in case of stable compound you will be able to remove it completely from its source with a limited amount of solvent. Hence, the advice is: have a try.

I was reading all these discussion and the same question was the reason for me to come to this page. I agree with all, that the method of extraction depends on the target compound or target activity. I was thinking whether it could be done to have the plant material extracted with both methods, may be first with Soxhlet and then same plant and same weight with solid- liquid extraction and a the end let pooled both extracts to get all the soluble compounds and also the thermally stable compounds.

I have one more related question, we normally concentrate the extract using rotary evaporation and that mean we are again exposing the thermally unstable compounds to heat, is there any other alternate method to avoid evaporation?