Kuliah 5- Derajat Kehalusan Serbuk

DERAJAT KEHALUSAN SERBUK

SIMPLISIA

• Makna ukuran partikel serbuk

• Teknik penyiapan serbuk simplisia

• Penyimpanan dan pengawetan

• Teknik analisis serbuk

Preservation of plant material• The plant material must first be preserved so that the

active compounds will remain unchanged during transport and storage.

• The cells of living plants contain not only low molecular-weight compounds and enzymes, but they also have many kinds of barriers that keep these constituents apart. When the plant dies, the barriers are quickly broken down and the enzymes then get the opportunity to promote various chemical changes in the other cell constituents, e.g. by oxidation or hydrolysis. Preservation aims at limiting these processes as far as possible.

A.A. DryingDrying• The most common method for preserving plant

material is drying.• Enzymic processes take place in aqueous solution.

Rapid removal of the water from the cell will, therefore, largely prevent degradation of the cell constituents.

• Drying also decreases the risk of external attack, e.g. by moulds.

• Living plant material has a high water content: leaves may contain 60-90% water, roots and rhizomes 70-85%, and wood 40-50%. The lowest percentage, often no more than 5-10%, is found in seeds.

• To stop the enzymic processes, the water content must be brought down to about 10 %.

• Drying must be done quickly, in other words at raised temperatures and with rapid and efficient removal of the water vapor.

• The most efficient drying is achieved in large driers of the tunnel type. The plant material is spread out on shallow trays, which are placed on mobile racks and passed into a tunnel where they meet a stream of warm air.

• The air temperature is kept at 20-40 °C for thin materials such as leaves, but is often raised to 60-70 °C for plant parts that are harder to dry, e.g. roots and barks.

• When the crude drug has been collected under primitive conditions, without access to a drier, it must be dried in the open. Even then, the material should be spread out in shallow layers with good ventilation to facilitate the drying. The choice of sunshine or shade is determined by the sensitivity to light of the constituents.

• In a dried drug the enzymes are not destroyed but In a dried drug the enzymes are not destroyed but only rendered inactive due to the low water content. only rendered inactive due to the low water content. As soon as water is added, they become active As soon as water is added, they become active again. Hence, dried drugs must be protected from again. Hence, dried drugs must be protected from moisture during storage.moisture during storage.

B. B. Freeze-dryingFreeze-drying

• Freeze-drying (lyophilization) is a very mild method.

• Frozen material is placed in an evacuated apparatus

which has a cold surface maintained at -60 to -80 °C.

Water vapor from the frozen material then passes

rapidly to the cold surface.

• The method requires a relatively complicated The method requires a relatively complicated

apparatus and is much more expensive than hot-air apparatus and is much more expensive than hot-air

drying. For this reason, it is not used as a routine drying. For this reason, it is not used as a routine

method, but it is very important for drying heat-method, but it is very important for drying heat-

sensitive substances, e.g. sensitive substances, e.g. antibioticsantibiotics and and proteins proteins.

Methods of drying

Drying is carried out either by natural or artificial methods.

1- Natural drying: this is accomplished by natural air in sun or shade.

2- Artificial drying: this is a rapid method done at well-controlled temperature and is accomplished by:

• direct fire.• Use of heated stones.• Use of stoves.

• Lyophilization (Freeze drying):

Frozen material is placed in an evacuated apparatus which has a

cold surface maintained at -60 to -80 °C. Water vapour from the

frozen material passes rapidly to the cold surface.

It is used for drying heat-sensitive substances e.g. antibiotics and It is used for drying heat-sensitive substances e.g. antibiotics and

proteinsproteins.

• Chemical drying using desiccators

• An absolutely dried drug is that completely freed from water, when exposed to air it absorbs 8-10% of moisture and is called air-dry drug.

C. C. StabilizationStabilization• On long storage, enzymic reactions will slowly destroy

the constituents, because the last traces of water can never be removed.

• In order to avoid this degradation, the enzymes should be destroyed before drying, a process usually called stabilizationstabilization.

• The most common method being brief exposure (a few minutes only) of the plant material to ethanol vapor under pressure (0.5 atm).

• Stabilization may be of value for the isolation of compounds that are very susceptible to enzymic degradation.

D. D. FermentationFermentation

• Enzymic transformation of the original plant

constituents is sometimes desirable.

• The fresh material is then placed in thick layers,

sometimes covered and often exposed to raised

temperatures (30-40 °C) and humidity, so as to

accelerate the enzymic processes. (This treatment is

usually called fermentation).

• The fermented product must, of course, be dried

afterwards to prevent attack by microorganisms, e.g.

moulds.

• Fermentation is mostly used to remove bitter

or unpleasant-tasting substances or to

promote the formation of aromatic

compounds with a pleasant smell or taste.

• It is mainly applied to drugs used as spices or It is mainly applied to drugs used as spices or

stimulants, e.g. vanilla, tea and cacao.stimulants, e.g. vanilla, tea and cacao.

Plants can be dried in a number of ways:

1. the open air (shaded from direct sun-light); 2. placed in thin layers on drying frames, wire-

screened rooms, or in buildings;3. direct sunlight, if appropriate; 4. in drying ovens/rooms and solar dryers; 5. indirect fire; 6. baking; 7. lyophilization; 8. microwave; or 9. infrared devices.

• Where possible, temperature and humidity should be controlled to avoid damage to the active chemical constituents.

• The method and temperature used for drying may have a considerable impact on the quality of the resulting medicinal plant materials.

• For example, shade drying is preferred to maintain or minimize loss of color of leaves and flowers; and lower temperatures should be employed in the case of medicinal plant materials containing volatile substances

• The drying conditions should be recorded. • In the case of natural drying in the open air,

medicinal plant materials should be spread out in thin layers on drying frames and stirred or turned frequently.

• In order to secure adequate air circulation, the drying frames should be located at a sufficient height above the ground.

• Efforts should be made to achieve uniform drying of medicinal plant materials to avoid mold formation

• Drying medicinal plant material directly on bare ground should be avoided.

• If a concrete or cement surface is used, the plant materials should be laid on a tarpaulin or other appropriate cloth or sheeting.

• Insects, rodents, birds and other pests, and livestock and domestic animals should be kept away from drying sites.

• For in-door drying, the duration of drying, drying temperature, humidity and other conditions should be determined on the basis of the plant part concerned (root, leaf, stem, bark, flower, etc.) and any volatile natural constituents, such as essential oils.

• If possible, the source of heat for directs drying (fire) should be limited to butane, propane or natural gas, and temperatures should be kept below 60 °C

• If other sources of fire are used, contact between those materials, smoke, and the medicinal plant material should be avoided.

3. Storage of crude drugs

• There are great differences in the stability of crude drugs because of slow enzymic changes in the constituents.

• Drugs containing glycosides and esters are usually less stable than those containing alkaloids.

• Drugs with essential oils deteriorate rather quickly through evaporation, oxidation and polymerization of the substances constituting the essential oil.

• Tannins on the other hand, have an almost unlimited durability.

• In order to keep crude drugs as long as possible:

1. It is essential to store them in a dry condition in

carefully closed containers.

2. It is also advisable to exclude light, because - even if

it does not affect the active constituents - it almost

always causes changes in the appearance of the

drug, especially loss of color.

3. It is also necessary to protect the drug against insect

attack.

Grinding of crude drugs

STEPS STEPS in in PREPARING PREPARING POWDERSPOWDERS

Particle Particle size size

reductioreductionn

Mixing of Mixing of PowdersPowders

Packaging Packaging

of of PowdersPowders

4. Grinding of crude drugs

• Regardless of whether the crude drug is to be used

for isolation of a pure compound or for manufacture

of a simple preparation, the first operation that must

be performed is grinding of the plant material to a

powder of suitable particle size.

• It is important that the particles are of as uniform a

size as possible.

• Excessive dust can clog percolators and result in a

turbid extract which is hard to clarify.

Particle Size Reduction

Comminution or grinding may be defined as the process of particle size reduction

• Large particles take a longer time for complete extraction than small ones and large differences in particle size thus slow down the extraction process.

• Several types of machines are available for grinding crude drugs:

1.1. Hammer millHammer mill; a common type for grinding crude drugs.

2.2. Knife millKnife mill; is useful for production of low-dust powders of leaves, barks and roots for subsequent percolation or maceration.

3.3. Tooth millTooth mill; is used for production of very fine powders.

• Grinding produces a certain amount of heat which must be observed when grinding crude drugs containing heat-sensitive compounds.

• Mills cooled with liquid nitrogen are available for such purposes.

• Cold grinding is also preferable for crude drugs containing volatile oils.

• Following grinding, the material must be sifted to ensure the proper particle size.

• Sifting can be performed according to two different Sifting can be performed according to two different

principlesprinciples: sievingsieving and blast siftingblast sifting.

• SievingSievingIn sieving the material is passed through a sieve of suitable mesh size giving two fractions. The fraction passing the sieve consists of particles with a size smaller than or corresponding to the mesh size. The remaining fraction consists of coarser particles which are returned to the mill for continued grinding.

• Blast siftingBlast siftingIn blast sifting the material to be classified is blown with compressed air into an apparatus which allows the particles to sediment according to their weight. Coarse, heavy particles settle fast whereas small, light particles stay for a long time in the air stream.

sieves

SIEVE SIEVE SIEVE SIEVE

NUMBER OPENING NUMBEROPENING

2.0 9.50 mm 70.0212.00 um

3.5 5.60 mm 80.0180.00 um

4.0 4.75 mm 100.0 150.00 um

8.0 2.36 mm 120.0 125.00 um

10.0 2.00 mm 200.0 75.00 um

20.0 850.00 um 230.0 63.00 um

30.0 600.00 um 270.0 53.00 um

40.0 425.00 um 325.0 45.00 um

50.0 300.00 um 400.0 38.00 um

60.0 250.00 um

OPENING OF STANDARD SIEVES

Particle Size AnalysisPowders of vegetable and animal drugs

• Very coarse (No.8)

• Coarse (no. 20)

• Moderately coarse (No. 40)

• Fine (No. 60)

• Very Fine (No. 80)

Particle Size AnalysisThe powders fineness for chemicals

• Coarse (No. 20)

• Moderately coarse (No. 40)

• Fine (No. 80)

• Very Fine (No. 120)

Purpose of particle size analysis

• To obtain quantitative data on the size, distribution, and shapes of drug and non drug components to be used in pharmaceutical formulation

Persyaratan WHO

Size of cut • Medicinal plant materials are used either whole, or in cut

or powdered form.• Cut medicinal plant materials are prepared by cutting or

crushing the plant into small pieces. The cut is graded according to the aperture size of the mesh of the sieve through which the material will pass, and is indicated as follows:

• Aperture size (mm)• coarse cut 4.00• medium cut 2.80• fine cut 2.00

Powder fineness and sieve size

• Powders• The coarseness or fi neness of a powder is classed according to the

nominal aperture size expressed in micrometres of the mesh of the sieve through which the powder will pass, and is indicated as follows:

• Descriptive term Particle size• Coarse (2000/355) All the particles will pass through a No. 2000

sieve, and not more than 40% through a No. 355 sieve• Moderately coarse (710/250) All the particles will pass through a No.

710 sieve, and not more than 40% through a No. 250 sieve• Moderately fi ne (355/180) All the particles will pass through a No.

355 sieve, and not more than 40% through a No. 180 sieve• Fine (180) All the particles will pass through a No. 180 sieve• Very fi ne (125) All the particles will pass through a No. 125 sieve

Sieves

• The wire sieves used to sift powdered medicinal plant materials are classified by numbers that indicate their nominal aperture size expressed in μm.

• The sieves are made of wire of uniform circular cross-section,

Sieves

Methods Of Determining Methods Of Determining Particle SizeParticle Size

SEDIMENTATION RATE, in which particles is determined by measuring the terminal settling velocity of particles through a liquid medium in gravitational or centrifugal environment

(range: 0.8-300 micrometers)

Light Energy diffraction, in which particle size is determine by the reduction in light

reaching the sensor as the particle, dispersed in a liquid or gas, passes through the sensing

zone (range: 0.2 - 500 micrometers)

Laser halography, in which a pulsed laser is fired through an aerolized particle spray and photographed in three dimension with a halographic camera, allowing the particles to be individually imaged and sized (range: 1.4 - 100 micrometers)

Cascade Impaction is based on the principle that a particle, driven by an airstream, will impact on a surface in its path, provided that its inertia is sufficient to overcome the drag force that tends to keep it in the airstream

SIEVING – particles are passed by mechanical shaking through a series of sieves (from 40 to 9500 micrometers, depending upon sieve sizes)

MICROSCOPY – particles are sized through the use of calibrated grid background or other measuring devise ( range 0.2 to 100 micrometers)