Technology for manufacturing medicinal herbs

Method of preparation

The process of preparing medicinal herbs usually includes the following stages:
— Preparation of medicinal herbs and solvents.
— Extract active ingredients.
— Eliminate impurities.
— Concentration, drying.
— Adjust the active ingredient content
— Complete preparations.

1.1. Preparation of medicinal herbs and solvents

Pharmaceutical materials must meet the prescribed standards. To ensure the quality of medicinal herbs, the following issues should be noted:
— Parts used as prescribed.
— The ratio of impurities in pharmaceutical materials.
— The level of microbiological contamination.
— Limit insecticides and preservatives.
— Limit sulfate ash, heavy metal.
Medicines are often dried and broken down to an appropriate fineness. The degree of division of a medicinal plant depends on the physical structure of the medicinal material, the diffusion ability of the solvent, the rate of solvent used and the time required to extract the medicinal material. For example, if it is necessary to quickly extract the active ingredient in a solidly structured medicinal material, it must be finely ground. Soft, porous and absorbent solvents may be extracted in a raw powder form. Depending on the part used, the degree of subdivision may apply as follows:
Leaves, flowers and herbs: small canopy (4 mm)
Logs, bark, roots: crowns (2.8 mm)
Fruit and seeds: small canopy (2 mm)
Medicinal materials containing alcaloid: finely pulverized (0.7 mm)
Some special herbs may have to kill yeast or the type of fat. Different medicinal powders can be mixed before extraction.
Solvents for drug preparation are usually water, ethanol, ethylic ether. Either use a mixture of ethanol — water or ethanol — ether. Water is a common and inexpensive solvent, but has the drawback of dissolving many impurities and difficult to preserve medicinal materials. Ethanol dissolves many active ingredients, dissolves less impurities, so it is more widely used, easier to preserve medicinal herbs. Ete is rarely used because it is expensive and flammable. Use ether in the case where the active substance is only soluble in ether, or used to remove impurities of oil, fat, wax in the extract.
To increase the solubility of the active substance, it is possible to acidify or alkaline the solvent with hydrochloric acid, acetic acid, ammonia, sodium hydroxide
The extracted solvent must meet the prescribed Pharmacopoeia standards. The water used for extraction must be purified according to the Pharmacopoeia standard or potable water.

1.2. Active ingredient extract

Depending on the nature of medicinal herbs and solvents, quality standards of finished products as well as equipment conditions and production scale, methods can be used: immersion, immersion, upstream extraction or other methods. Other appropriate measures.
If the solvent is water, the fractional immersion method (cold soaking, tunneling, braking, sharpening) is often used, and the infusion method is seldom used. The amount of water is usually 8–12 times the amount of medicinal herbs. Solvents are ethanol, ethers usually apply the depletion method. Selecting the alcohol content depending on the composition of the medicinal material. Herbal ingredients containing water-soluble active ingredients using 30o-60o ethanol; pharmaceutical materials containing alcaloid, glycoside using ethanol 70o; medicinal herbs containing essential oils, myrrh with ethanol 80o-900; pharmaceutical materials with active ingredients easily hydrolyzed using 90o-95o ethanol.
The amount of solvent normally used is 6 times the amount of medicinal material.

1.2.1. Method of cold immersion:
Add the finely divided medicinal ingredients to the appropriate fineness (usually coarse powder) and the solvent in a closed container at room temperature. Soak for a specified time; stirring or shaking occasionally. Then decant, pressing residue to extract extract. Leave for 2–4 days in a cool place to remove suspended impurities. Decant, filter for clear fluid. Can be soaked simply or soaked in segments.
— Simple soaking: soak once with the entire amount of solvent.
— Soaking segments: divide solvent into many parts and then soak many times. After each soak, decant the extract, press the residue, add new solvent to soak and continue as above. Finally concentrate the extracts. With the same amount of solvent, fractional immersion draws more active ingredients than simple immersion.
The method of cold immersion is used for medicinal materials that contain highly soluble or easily degradable active ingredients at high temperatures.

1.2.2 Method of immersion (dripping):
Drip soaking is a method of extraction by allowing the solvent to flow very slowly through a block of medicinal material contained in a special device called an empty flask. The extraction process has no stirring.

* Principles of the method:
When the solvent is added to the medicinal powder, due to gravity gravity flows down the gaps. During the time the solvent is retained and in contact with medicinal herbs, the active substance is dissolved. Then add a new solvent to the surface of the medicinal herbs block, this layer of solvent seeps into the medicinal material block and pushes the extract (the old solvent layer of dissolved medicine) out. The new solvent layer continues to dissolve the active ingredient in the medicinal cell. The process continues until no more solvents are added. This means that it is always exposed to new solvents so that the active ingredient can be extracted.
Soak dripping includes the following stages:

* Preparation of medicinal herbs:
Medicines need to be dry and broken down to an appropriate fineness. As in the immersion method, it is necessary to minimize the proportion of fine powder when subdividing medicinal herbs. Very fine medicinal materials easily blend into the extract and easily cause clogging of the extraction flask.

* Moistening medicinal herbs:
The purpose of this stage is to allow the dried medicinal herbs to absorb the solvent and swell completely before being transferred to the extraction flask. If the medicinal herbs are not fully moistened and swelled, they will continue to swell in the extraction flask, creating a compact block that prevents the solvent from permeating. Moreover, if the medicinal herbs are not previously moistened, it will be difficult to transfer the air out of the medicinal herbs into the extraction flask, creating gaps that prevent pharmaceuticals from coming into contact with the solvent, reducing the extraction efficiency.
In a suitable device, mix the medicinal plant with a sufficient amount of solvent to provide adequate moisture. The amount of moisturizing solvent depends on the ability of solvent extraction and expansion of the medicinal powder, usually 50–100% of the extracted medicinal herbs.
Mix the herbs with the solvent, cover tightly to stand for 2–4 hours then sieve through a sieve with a large sieve size to spread the powder. It is also possible to moisten the medicinal plant in an empty container if the medicinal material is less swollen and the extraction bottle has an appropriate design.

* Soak intermediates:
Gradually moisten the medicinal herbs in a layer one by one, gently compress and level the surface of the dough. For uneven pharmaceutical materials will create channels, the solvent flows along those channels without being evenly permeable through the entire dough block. Place a filter paper and other objects on top of it, so that the solvent is evenly distributed and avoid mixing up the medicinal material. Then open the valve at the bottom of the flask, add the solvent until all the air is released and the extract begins to drain. Close the valve and add solvent for medicinal herbs to soak for 24 hours or longer depending on the medicine.

* Withdrawal of extract:
Open the extract and allow the extract to drop into the flask. Pay attention to the addition of solvent regularly to cover the surface of medicinal herbs 2–3 cm. The rate of extraction of the extract depends on the volume and nature of the medicinal material used. Too fast withdrawal will not exhaust active ingredients; too slow extraction, prolonged extraction time and solvent loss due to evaporation. For a batch of 1000 g of medicinal herbs, the slow rate of withdrawal is about 1 ml / minute, an average of 1–3 ml / minute and fast as 5 ml / minute.
Immersion method is often used to extract medicinal herbs with strong toxic active ingredients. The extraction solvent is usually alcohol or ether. Medicinal materials that contain a lot of glue, starch, and mucus should not be applied with water-based solvents. The method has the advantage of consuming less solvents and extracting the active ingredient. Segmented exhaustion:

* The above method of depletion is called simple depletion, which always uses a new solvent to extract the active ingredient. Fractional staging method uses dilute extract to extract new medicinal material.
Medicinal materials are divided into many pots, evenly or gradually smaller (for example, 1000 g of herbs divided into three bottles of 500 g, 300 g, 200 g). Proceed with the extraction as described above, but the first extract of flask I (equal to 80% of the medicinal ingredient) is left alone; The next extract is used as a humidifier and extracts the medicinal material in flask II. The first extract of flask II is equal to the amount of medicinal herbs in the jar separately; The second extract of flask II is used again as solvent extracting flask III, continue as above until the end.
This method has the advantage of consuming less solvents and obtaining concentrated extract, but the downside is that it does not exhaust the active ingredients.

1.3 Eliminate impurities:

When extracted with water or ethanol, the extract usually contains many impurities. Impurities are necessary because they are easily degradable, affecting the quality of medicinal herbs. Medicinal materials will be unstable and have a strange smell. When mixing medicinal materials into water, the solution will not be clear. In the case of preparing solid and dry medicinal herbs, if the content of active ingredients is not enough, it may be necessary to remove impurities.
The type of impurity method depends on the impurity nature of the extract, that is, the nature of the medicinal material, the type of solvent and the extraction method. However, there are some general methods as follows:

• Water-soluble impurities (usually protein, gum, mucus, pectin, starch)
— Thermal method: concentrate the extract to 1/2–1/4 of the original volume, let it cool and then filter. If the extract is cloudy, add crushed filter paper pulp or talcum to the extract, boil and filter. This can eliminate proteins, mucus and other substances that are prone to heat clotting.
— Method of using ethanol: concentrate the extract until the ratio of about 2 kg of raw material / 1 liter of extracted water, add 2–3 times the volume of ethanol 95o, stir well, to settle in a cool place and then decant. Distill ethanol and then concentrate to a specified volume. This method can remove mucus, albumin, gum.
— pH adjustment method: concentrated extract is adjusted to pH ≈ 12, most of the active substances and impurities will precipitate, when the acid is added to have pH = 5–6, some of the active substances dissolve again. also most impurities do not dissolve. This method is usually applicable to extracts containing active ingredients flavonoids, alcaloid.

• Ethanol-soluble impurities (plastic, fat).
— Concentrate the extract to lower the alcohol, resin and fat content to precipitate. To eliminate them more thoroughly, double dilute with water (or acid water if the active ingredient is alcaloid), or add 2% talcum powder to adsorb impurities and facilitate it to precipitate.
— Use paraffin: extract concentrated concentrated remaining 1/2–1/4 of the original volume, add paraffin to hot extract, stir thoroughly and allow to cool. Pick up the dissolved paraffin layer.
— Alternatively, ether can be used to extract fat and plastic from aqueous extracts.

1.4 Concentration and drying

In order to prepare medicinal herbs, solvent evaporation is usually carried out. For liquid medicinal herbs, concentrate the extract to the prescribed ratio (1 ml of liquid pharmaceutical materials corresponds to 1 g of medicinal herbs). When extraction by upstream or exhaustion, to avoid the effects of heat, the concentrated first extract portion should be kept separate (this part contains a large amount of extractable active ingredient). Then concentrate the subsequent extracts and combine with the first extract.

Various concentrating and drying equipment may be used, but it is preferable to proceed at reduced pressure and at a temperature such that the minimum degradation of the active ingredient (usually not more than 600 ° C). Avoid drying or prolonged drying at high temperatures.

1.5 Determining and adjusting the active ingredient ratio

For pharmaceutical materials with prescribed content, the amount of active ingredient must be quantified after preparation, if necessary, it must be adjusted so that the medicinal material has the prescribed active ingredient ratio.
In case of liquid pharmaceutical materials with lower active ingredient ratio, proceed to evaporate to remove solvent. If the active ingredient content is higher than prescribed, it may be diluted with an appropriate solvent.
Solid and dry medicinal herbs with lower than the active ingredient content must be diluted with solvents or removed impurities. If higher than the regulation can use inert fillers such as dextrin, lactose, starch or pulverized pulp. The amount of adjuvants is calculated by the following formula:
x = (100-R) .a / b — T
Inside:
a: amount of active ingredient (g) in herbal ingredients
b: the prescribed active ingredient content (%)
R: permissible moisture content (%)
T: dry bite weight of total medicinal ingredient (g)
x: weight of padded adjuvants needed (g)
To ensure uniformity when adding filler excipients, the following can be done:
— Extract the extract to a soft medicinal material. Weigh and determine dry bite rate and active ingredient content. From there, calculate the amount of filler excipients to use. After adding adjuvants, soft herbs are dried until the desired moisture content is reached.
— In case the dry medicinal ingredient has reached the prescribed moisture content, it is possible to add padded adjuvants by grinding together with the dried medicinal herb.
In addition to adjusting the content of active ingredients in medicinal herbs, this can be done by combining batches of medicinal materials with different active ingredient content.

1.6 Complete preparations

- Liquid medicine for drinking can add flavor enhancers such as single syrup, menthol, essential oil, vanillin …
— Add preservatives against mold such as boric acid, benzoic acid, sodium benzoate, nipagin, nipasol. Adding preservatives to herbs is usually done at the end of the concentrate.

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