1

DECOCTION AND HOT CONTINUOUS EXTRACTION

TECHNIQUES

Sudeep TandonScientist

Chemical Engineering Division CIMAP, Lucknow

Decoction is a waterDecoction is a water--based preparation to extract based preparation to extract active compounds of herbs, made by boiling the active compounds of herbs, made by boiling the plant parts for some period.plant parts for some period.Used to primarily extract the mineral salts and Used to primarily extract the mineral salts and bitter principles of plants, rather than vitamins and bitter principles of plants, rather than vitamins and volatile ingredientsvolatile ingredientsIt is a liquid preparation made by boiling the herbs It is a liquid preparation made by boiling the herbs with water, differing from infusions that the latter with water, differing from infusions that the latter are not actively boiled are not actively boiled Decoctions are usually the method of choice when Decoctions are usually the method of choice when working with tougher and more fibrous plants, working with tougher and more fibrous plants, barks and roots (and which have water soluble barks and roots (and which have water soluble chemicals).chemicals).

INTRODUCTION

2

•• Instead of just steeping it in hot water, the plant Instead of just steeping it in hot water, the plant material is boiled for a longer period of time to soften material is boiled for a longer period of time to soften the harder woody material and release its active the harder woody material and release its active constituentsconstituents

•• The plant materials are generally into broken into The plant materials are generally into broken into small pieces or grounded into a powdersmall pieces or grounded into a powder——the smaller the smaller they are, the more easily they will be absorbed into they are, the more easily they will be absorbed into the waterthe water

•• More heat is needed in making decoctions than More heat is needed in making decoctions than infusions, since mostly the parts of the herb that are infusions, since mostly the parts of the herb that are used in decoctionsused in decoctions——the bark and rootsthe bark and roots——are very are very dense in nature. dense in nature.

•• Unfortunately, the high heat does tend to destroy Unfortunately, the high heat does tend to destroy some of the herb's volatile oils.some of the herb's volatile oils.

Methods of preparing decoctionsMethods of preparing decoctions

Different methods have been described in literature for preparation of decoctions…

3

METHOD FOR PREPARING DECOCTIONS IN TSM / METHOD FOR PREPARING DECOCTIONS IN TSM / AYURVEDAAYURVEDA

• Traditionally known as ‘KWATHA’

• Methodology : The Drug in form of ‘Yavakuta’ (small pieces taken in earthen pots or tinned cooper vessel with clay on outside

If drug is soft- 4 times water

If drug is moderately hard – 8 times water

If drug is very hard – 16 times water

• Then boiled on low flame till reduced to

1/4th in case of soft drugs

1/8th in case of moderately or very hard drugs

• Cooled, strained and filtrate collected in clean vessels

To prepare a decoction, select a ceramic pot (Material can vary) with a snug fitting lid. Measure the amount of herb needed into the pot and add the proper amount of cold water depending on how many cups of the decoctionyou wish to prepare. Turn on the heat to medium high and bring to a boil. Place the lid on the pot and reduce the heat to medium or medium-low so that the mixture stays at a good simmer. Simmer it covered for certain fixed time or till volume of waterreduces to fixed ratiosRemove from heat and cool slightly. If using cut herbs, strain the mixture through a strainerWhen straining, make sure to press on the cut herb pieces in thestrainer to get as much liquid/decoction out of the herb pieces as possible.If using powdered herb, allow the powder to settle to the bottom of the pot and then pour off the decoction from the top

IN ANOTHER METHOD DESCRIBED ELSEWHERE …….…

4

STRONG DECOCTIONS

• Depending on the type of plant material used, strong decoctions are prepared in two general ways.

• The first involves boiling the mixture longer. This is usually indicated when working with larger woody pieces of bark. Longer boiling time, up to 2 hours or more, is sometimes necessary to break down, soften, and extract the larger pieces.

• Alternatively, when smaller woody pieces are used yet a stronger remedy is wanted, the decoction is prepared as above (boiling 20 minutes), then it is allowed to sit/soak overnight before straining out the herb.

• Only Recently prepared decoctions should be dispensed

• Decoctions should be stored under refrigerated conditions

• The drug concentration of a decoction should be well specified for the plant material or should be prescribed by a physician

If drug concentration is not specified then following general formula of USP XII can be used

• The Drug, coarsely comminuted …………….. = 50 gm

• Water, sufficient quantity………………...to make 1000 ml

Method

• Place the drug in a suitable vessel provide with a cover

• Pour upon t 100 ml of cold water, cover it and boil for about 15 min

• Allow to cool to 40oC

• Strain and use as such or dilute again to 1000 ml

5

Extraction with Volatile solvents

Mainly applied for

Medicinal plants /herbs for preparation of standardized extracts / total crude extracts like alkaloids, saponins, glycosides etc

Extracts which contain bio active constituents for further downstream processing and isolation of the pure phytomolecules

Aromatic plants mostly florals like rose, jasmine, tuberose for preparation of concretes and absolutes

Spices or spice plants for preparation of the oleoresins / resenoids

6

Solvent Extraction of herbs fall in category of solid liquid extraction and is also referred as the leaching processLeaching is the process of removing a solute from a solid by theuse of a liquid solvent.The separation usually involves selective dissolution, with or without diffusion.Lixiviation is also used less frequently as a synonym for leachingThe insoluble solid may be massive and porous; more often it is particulate, and the particles may be openly porous, cellular with selectively permeable cell walls, or surface-activated. The stream of solids being leached and the accompanying liquid is known as the underflowThe solid content of the stream is sometimes called marc.The stream of liquid containing the leached solute is the overflow

• When solvent penetrates into plant material it is necessary, to verify the diffusion process. i.e. the mass transfer of the product from the solid phase to the liquid.

• The rate of mass (Δ m) transfer in the time dt is a function of surface contact between the phases (S), of the coefficient diffusion of the solute in the solution (D) and of the concentration of the solute in the liquid (C) to the time t and in the liquid film around the solid that we are extracting (Cs) as well as the thickness of the liquid film around the solid matrix (S).

PRINCIPLE OF SOLVENT EXTRACTION

ΔΔM = SD (Cs M = SD (Cs –– C) C)

ss

• The practical interpretation of leaching equilibrium is the state in which the overflow and underflow liquids are of the same composition; on a y-xdiagram, the equilibrium line will be straight line through the origin with a slope of unity.

• It is customary to calculate the number of ideal (equilibrium) stages required for a given leaching task

Concept of Equilibrium

7

MECHANISMS OF EXTRACTIONSingle Stage Extraction :

EXTRACTION STAGE

FRESH SOLVENT

SOLID UNDERFLOW

OVERFLOW SOLUTION

SOLID FEED

TWO STEPS ARE ALWAYS INVOLVED IN SOLID LIQUID EXTRACTION

1. Contact of liquid solvent with the solid to effect transfer of solute from the solid to the solvent.

2. Separation of resulting solution from the residual solid.Two other auxiliary operation are involved namely :

a) Preparation of the solid for extraction and b) Recovery of solute form the solvent, usually by evaporation or distillation of solvent from the solute

Extraction Stage 1

Extraction Stage 2

Extraction Stage n

Fresh Solvent

Solid Feed

Fresh Solvent Fresh Solvent

Overflow Solution Overflow SolutionOverflow Solution

Solid Under flow

Extraction Stage1

Extraction Stage n

Extraction Stage 2

Fresh Solvent

Solid Under flow

Overflow Solution

Solid Feed

Multistage Counter current Extraction

Multistage Co current Extraction

8

• MATRIX CHARACTERISTICS

• CHOICE OF SOLVENT

• METHOD OF CONTACTING

• TEMPERATURE OF EXTRACTION

• NUMBER OF WASHES

• CONDITIONS FOR EXTRACTION-AGITATION

PROCESS PARAMETERS EFFECTING SOLID LIQUID / SOLVENT EXTRACTION

MATRIX CHARACTERSTICSMATRIX CHARACTERSTICSSolvent extraction strongly depends on matrix characteristics and particle size as the internal diffusion may be limiting step during extraction.Many pharmaceutical products recovered from plant roots, stems and leaves, the plant material is frequently dried before treatment, and these does much toward rupturing the cell walls and releasing the solute for direct action by the solvent.The cells are, of course smaller than this, but they are largely ruptured by the flaking process, and constituents are then more rapidly contacted by the solvent.

The degree of comminution required will also depend on the composition of the crude drug e.g.

is it hard or soft ?, is it thick or thin ?

If the drug is leaves or petals then it will be easily penetrated by the solvent, therefore the degree of comminution need not be great, whereas hard and woody substances will require a greater reduction in size.

9

CHOICE OF SOLVENT :

Selectivity : Wt fraction of solute in Residue Wt fraction of solute in Extract

Selectivity must exceed unity (i.e. > 1) the more so better.

Insolubility / Miscibility of SolventLow boiling point and high volatility for better Recoverability PolaritySolvent should be non toxicNon flammable & low cost Non Denaturing natureChemically non-reactive towards the product being extractedECOFREINDLY

β =

10

100#0.06110.6tolune

400M ?82.42-propanol

400M911-propanol

200#∞64.7Methanol

-∞290*Propantriole

500-30-50Petrol ether

4001.234.6Ethyl ether

1000∞78Ethanol

-T69Hexane

100.876.77Carbon tetrachloride

50861Chloroform

22001.339.7Dichloromethane

300T80.7Cyclohexane

22001979.5Buthan-2-one

25T80Benzene

4008077Ethyl Acetate

10∞116-117Aceric Acid

1000∞56Acetone

TLVbMiscibility with H2 OBP (OC)Solvent

b - p.p.m .t = < 0.01%, * = with decomposition; m = miscible,∞ = completely miscibleTLV : Threshhold Limit Values

SOME COMMON SOLVENTS USED FOR EXTRACTION OF MAP’S

TEMPERATURE

Higher temperatures results in greater solubility of solvents anHigher temperatures results in greater solubility of solvents and d therefore are sometimes desirable to realize higher solute therefore are sometimes desirable to realize higher solute concentration in the extract. concentration in the extract. The temperature of the extraction should be chosen for the best The temperature of the extraction should be chosen for the best balance of solubility, solventbalance of solubility, solvent--vapor pressure, solute diffusivity, vapor pressure, solute diffusivity, solvent selectivity, and sensitivity of product.solvent selectivity, and sensitivity of product.Elevated temperature, in case of some natural materials may Elevated temperature, in case of some natural materials may result in excessive extraction of undesirable material. result in excessive extraction of undesirable material. Use of high temperature during extraction is avoided when the Use of high temperature during extraction is avoided when the active constituents are thermo labile or volatile and to reduceactive constituents are thermo labile or volatile and to reduce the the level of unwanted constituents.level of unwanted constituents.Higher temperature operation may also not be permissible Higher temperature operation may also not be permissible

because of solvent losses and for safety considerationbecause of solvent losses and for safety consideration..

11

METHOD OF SOLID LIQUID CONTACTING

In fixed bed contacting, the solid particle are stationary, While dispersed contact involve motion of solid particles relative to each other and also relative to liquid. Solvent may be contacted with a fixed bed of solids in three different ways:1) Spray Percolation2) Full immersion 3) Intermediate drainage.

Solid – Liquid Extraction: Equipments

Can be divided into two main classes :

1) Those in which the leaching is accomplished by percolation (Passing the solvent through a bed of static particulate material)

2) Those in which particulate solid are dispersed into a liquid andsubsequently separated from it.

EACH CAN BE EITHER BATCH AND CONTINUOUS EACH CAN BE EITHER BATCH AND CONTINUOUS UNITS.UNITS.

12

PERCOLATION PERCOLATION

Percolation is generally carried out in batch tanks and in continuous or dump extractors (usually on smaller scale).

COLD PERCOLATION :

This method allows processing of the herbs into a liquid extract without utilizing heat or concentration, both of which may cause damage to the constituent of the whole herb. It is referred to as soft extraction technique.

HOT PERCOLATION :

In this method the bio-mass is added to the container containing the solvent and the mixture is heated under reflux. The technique is sometimes referred to as total extraction.

BATCH PERCOLATORS

The batch tank is not unlike a big nutsche filter; it is a large circular or rectangular tank with a false bottom. The solids to be leached are dumped into the tank to a uniform depth. They are sprayed with solvent until their solute content is reduced to an economic minimum and are then excavated. Countercurrent flow of the solvent through a series of tanks is common, with fresh solvent entering the tank containing most nearly exhausted material.

CONTINUOUS PERCOLATORSCoarse solids are also leached by percolation in moving-bed equipment, including single-deck and multideck rake classifiers, bucket-elevator contactors, and horizontal-belt conveyors.

13

Vessels with Agitation

• Channeling of the solvent in percolation of fixed bed, with its consequents slow and incomplete leaching, can be avoided by stirring the liquid and solid in leaching vessel.

• The agitation vessel is generally used for coarse solids

• This device is operated in batch wise fashion and provides a single leaching stage.

Percolation Vs. Agitation• If a solid in the form large lumps is to be leached, a decision must frequently be

made whether to crush it coarse lumps and leach by percolation or whether to grind it fine and leach by agitation

• Fine grinding is more costly but provides more rapid and possibly more thorough leaching.

• Coarsely ground particles, on the other hand .Leach more slowly and possibly less thoroughly but on draining may retain relatively little solution., require less washing, and thus provide a more concentrated final solution.

• Leaching is generally more efficient in a thoroughly agitated vessel then by percolation, probably because the large amount of static liquid holdup makes important amounts of solute unavailable.

• Agitation operates in stage wise or in continuous- contact fashion. • Stage wise equipment is sometimes assembled in multiple units to produce

multistage effects, whereas continuous-contact equipment may provide the equivalent of many stages in a single device.

14

Classical technique for the solvent extraction of nutraceuticals from plant matricesThe plant material is placed in a thimble-holder, and filled with condensed fresh solvent from a distillation flask. When the liquid reaches the overflow level, a siphon aspirates the solution of the thimble-holder and unloads it back into the distillation flask, carrying extracted solutes into the bulk liquid. In the solvent flask, solute is separated from the solvent using distillation. Solute is left in the flask and fresh solvent passes back into the plant solid bed. The operation is repeated until complete extraction is achieved.

A schematic representation of a Soxhlet extractor

SOXHLET EXTRACTORSoxhlet extractor : a bench scale Laboratory apparatus invented in 1879 by Franz von Soxhlet.

Advantages and disadvantages of Soxhlet ExtractionAdvantages :

The displacement of transfer equilibrium by repeatedly bringing fresh solvent into contact with the solid matrix.

Maintaining a relatively slightly high extraction temperature with heat from the distillation flask.

No filtration requirement after leaching. Also, the Soxhlet method isvery simple and cheap.

Disadvantages :

The extraction time is long.Agitation can not be provided in the Soxhlet device to accelerate theprocess. The large amount of solvent used requires an evaporation concentration

procedure.The possibility of thermal decomposition of the target compounds cannot be ignoredAs the extraction usually occurs at the boiling point of the solvent for a long

time

15

LARGE SCALE CONTINUOUS TYPE EXTRACTORS

The Bollman-type extractor.

Rotocel extractor.

Kennedy extractor.

Screw-Conveyor Extractors.

Hildebrandt total-immersion extractor.

Most of the above type extractors find applications in the metallurgical industries for ore extraction and leaching.

Some extractors however have been used for vegetable oil extractions

16

Accelerated solvent extraction (ASE) is a solid–liquid extraction process performed at elevated temperatures, usually between 50 and 200oC and at pressures between 10 and 15 MPaAccelerated solvent extraction is form of pressurized solvent extraction

that is quite similar to SFE.Extraction is carried out under pressure to maintain the solvent in its liquid state at high temperature.Technique still in experimental stages

ACCELERATED SOLVENT EXTRACTION

ADVANTAGES AND DISADVANTAGES OF ASE

ADVANTAGES

Use of non toxic extracting solvents such as carbon dioxide andwater has economic and environmental benefits. Accelerated Solvent extraction is considered as a potential alternatives technique to SFE for extraction of polar compound. Compared with traditional Soxhlet extraction, there is a dramatic decrease in the amount of solvent and the extraction time for ASE

DISADVANTAGES

Accelerated solvent extraction performed with high extraction temperature, which may lead to degradation of thermo labile compounds.

17

LIQUID LIQUID EXTRACTION

SEPARATION OF A COMPONENT FROM A LIQUID MIXTURE BY TREATMENT WITH A SOLVENT IN WHICH THE DESIRED COMPONENT IS PREFERENTIALLY MORE SOLUBLE.Solvent : The liquid with which the feed is contacted with.Extract : The solute rich solvent product of the operation.Raffinate : Residual liquid from which solute has been removed.In liquid liquid extraction the products recovered have to be subjected to further

MT operations like distillation, crystallization, chromatography etc. for final recovery.

SOLVENT

FEED

EXTRACT

May be batch or continuousMixer Settlers e.g. Kerr-McgreeExtractor

SINGLE STAGE EXTRACTION

RAFFINATERAFFINATEMIXER

SEPARATOR1

MIXER SEPARATOR

2

MIXER SEPARATOR

‘n’

FEED

SOLVENT

EXTRACT EXTRACT EXTRACT

SOLVENTSOLVENT

RAFFINATE

CO-CURRENT FLOW EXTRACTION SYSTEM

COUNTER CURRENT FLOW EXTRACTION SYSTEM

RAFFINATERAFFINATEMIXER

SEPARATOR1

MIXER SEPARATOR

2

MIXER SEPARATOR

‘n’FEED

SOLVENT ENRICHED

WITH PRODUCT

SOLVENT

DEPLETED RAFFINATE

MULTI STAGE EXTRACTION

• Rotating Disc Contactors• Perforated Plate ( Karr Column)• Pulsed Plate Columns• Scheibel Extractors• Centrifugal Counter current “ Podbielniak Extractor”

Different types of liquid liquidextraction columns

18

HORIZONTAL LIQUID LIQUID‘PODBIELNIAK EXTRACTER

M

VERTICAL RECIPROCATING LIQUID LIQUID EXTRACTION “ KARR”

COLUMN

LARGE SCALE SOLVENT EXTRACTION UNIT

Basic equipments of an extraction unit consists of

• Drug holders / Extractors• Solvent Storage Vessel• Reboiler Kettle• Condensers• Breather system• Infrastructure• Boiler• Refrigerated Chilling unit• Vacuum • Inert Gas

In Industry Solvent Extraction units for MAPs is based on

‘Soxhlet principle with recycling of solvents

19

DESIGNING A SOLVENT EXTRACTION PLANT FOR HERBS !

High Efficiency of ExtractionMinimal Solvent lossesFacility for cold / hot extractionExtraction with agitationMultiple solvent extraction systemMultiple fraction collectionOnline filtration unitSolvent recycling and condensing unitVent lines with breather for minimizing solvent losses and safety Brine circulation unitFractionating column for separation of solvent mixturesEfficient evaporating systems like falling film, wiped film or rotary evaporators to work under low pressuresVacuum systems with cold trapsGMP Compatible : All Stainless Steel units

IMPORTANT FACTORS WHILE SETTING UP AN EXTRACTION

UNIT

20

JasmineFlowers

Percolation Vessel

Perforated Grid

Line Filter

Solvent

Recovered Solvent

Cooling Water

Condenser

SteamVacuum Concentr

ator

Extract

Rotary Vacuum Evaporator

ToVacuum

Jasmine Concrete

Absolute AlcoholChilling

Plant

FiltrationJasmine Absolute

Production of jasmine absolute using solvent extraction technique

SteroidDiosgeninRhizomesDioscoria deltoidea

TonicStimulant

BaccosidesWhole plantBacopa munnerai

TonicStimulant

AsiaticosidesAspatic acid

Whole PantCentella asiatica

Anti inflammatory

AescinSeedsAesculus indica

Gout, Rheumatism

ColchicineRhizomesGloriosa superba

HepatprotectiveDi terpenoidsAndrographalides

LeavesAndrographis panniculata

Skin diseasesLeucoderma

XanthotoxinSeedsAmmi majus

StimulantAntiinflamatory

Somniferum, PhytosterolRootsWithania somniferum

HypertensiveSedative

Resperine, RescinnamineRootsRauvolifolia serpentine

InsecticidalPyrethrinsFlowersChyrysanthemumcinerariaefolium (Pyrethrum)

AnticancerAjmalcine,VinblastineVincrystine

RootsLeaves

Cantharanthus roseus(Periwinkle)

LaxativeSennosides A & BLeaves, PodsCassia augustifolia (senna)AntimalarialArtemisininWhole PlantArtemesia annua (Quinghasou)

Major UseActive ConstituentUseful Plant Part

Plant

SOME IMPORTANT MEDICINAL PLANTS & THEIR ACTIVE CONSTITUENTS (That are extracted / isolated by Solvent Extraction technique)

21

SOLVENT EXTARCTION PLANTSOLVENT EXTARCTION PLANT

SOLVENT EXTARCTION PLANT FOR MAP’S AT BIOTECH PARK LUCKNOW

22

DRUG HOLDERS / EXTRACTORS