Syrups can be divided into the following categories according to the different components and uses:
Single syrup: It is a nearly saturated aqueous solution of sucrose with a concentration of 85%(g/m 1). Does not contain any medicine, and can be used as a raw material for preparing medicinal syrup, and can also be used as a flavoring agent and suspending agents.
Medicinal syrup: concentrated sucrose aqueous solution containing drugs or medicinal extracts. It has certain therapeutic effect. Its sugar content is generally above 65%.
Aromatic syrup: concentrated sucrose aqueous solution containing aromatic substances or fruit juice. Mainly used as flavoring agent for liquid medicine.
(a) Sucrose in syrup The raw material sucrose used to prepare syrup should meet the requirements of Pharmacopoeia. Sucrose belongs to disaccharide. Its aqueous solution is relatively stable, but in the presence of acid, it is easy to convert and hydrolyze after heating to form converted sugars (glucose and fructose). These two monosaccharides exist more or less in syrup with the heating time. Inverted sugar has reducibility and can delay the oxidative deterioration of some easily oxidized drugs. However, too much invert sugar also affects the stability of syrup. Therefore, some pharmacopoeias stipulate that the converted sugar should not exceed 0.3%.
The additives used, such as preservatives, odorants and cosolvents, should meet the requirements of medicine or health law.
(b) Preservatives in syrups The main additive in syrups is preservatives. Syrups with low sugar content are easy to proliferate microorganisms, and yeasts and molds in the air can cause fermentation, mildew, rancidity and turbidity to syrups. Appropriate preservatives should be added to prevent them.
Preservatives commonly used in syrup include carboxylic acids and nipagin. 0.1~ 0.25% benzoic acid and 0.05 ~ 0.15% sorbic acid are commonly used in carboxylic acids; Propionic acid can also be used. The sodium salts of these three carboxylic acids can also be used, but the concentration should be increased. For example, the common concentration of sodium benzoate is 0.15-0.35%. Chemically, the three carboxylic acids are low-grade fatty acids, which rarely ionize in aqueous solution, and most of them remain in molecular state, and their inhibition on microorganisms is mainly in molecular state. Therefore, when such preservatives are used, the effect is better under acidic conditions.
The acceptable dose for human body is 5.0 mg/kg d for benzoic acid, 5.0 mg/kg d for sorbic acid and10 mg/kg d for propionic acid.
Nipagin has stronger inhibitory effect on mold than carboxylic acid, but less inhibitory effect on yeast than carboxylic acid, and weaker inhibitory effect on bacteria. The dosage of this kind of preservative is low in toxicity, and it is widely used for the preservation of syrups and decoctions. It is suitable for weakly acidic and neutral liquid medicines, but the effect of being slightly acidic is still better. The optimum pH value of the medium is below 6.0 for methyl ester and ethyl ester, and below 7.0 for propyl ester. When it exceeds the limit, the anticorrosion effect is weakened.
In the aqueous solution with pH value of 3.0 ~ 6.0, methyl ester is stable when heated by 1000C for 2h or 1200C for 30min. However, when the pH value rises, its decomposition can be measured after heating. The accelerated test of chemical kinetics is used to calculate that the half-life of methyl ester is different at 250C under different pH conditions. Nipagin in aqueous solution, when the pH value is above 7.0, has obvious decomposition after heating, and propyl ester is more stable than methyl ester.
When the liquid medicine contains low concentration of propylene glycol, the effect of nipagin can be strengthened. When 0. 1-0 18% of methyl ester and 0.25% of ethyl ester are added to the inner 45% syrup, the antiseptic effect on mold and yeast is not significant. For example, when 2-5% propylene glycol is added, the antiseptic effect is significantly improved, but when 2-5% propylene glycol is used alone, there is no antiseptic effect.
When ethanol exists in the syrup of alcohol leaching preparation, it also has auxiliary antiseptic effect, and a certain concentration of ethanol is often retained in the finished product. It is generally considered that the suitable antiseptic concentration is15 ~ 25%.
Volatile oils or their components have different degrees of auxiliary antiseptic effect and aromatic corrective effect, such as cinnamon oil, eucalyptus oil, orange peel oil, lemon oil or cinnamaldehyde, perillaldehyde and so on. The commonly used amount of volatile oil is about 0.06%; 0.01%cork aldehyde can inhibit mildew; 0. 1% can inhibit fermentation, and the effect can be enhanced when the volatile oil is mixed. For example, the mixed preservative of 0.04% orange peel oil, 0.01%star anise oil and 5% ethanol can inhibit mildew and fermentation.
Preparation of syrup
Hot dissolution method: Weigh sucrose according to the prescription, add appropriate amount of boiling distilled water, heat and stir to dissolve, then add soluble drugs, dissolve and filter, and add appropriate amount of distilled water from the filter to the specified volume.
The advantage of this method is that sucrose raw materials often contain a small amount of protein, which can be solidified and easily filtered by heating, and can kill microorganisms, which is beneficial to preservation. However, attention should be paid to avoid heating rabbits for too long, otherwise the increase of invert sugar will easily lead to fermentation and coking, and the color will deepen. Therefore, it is best to grasp the limit of 5 minutes after boiling, and filter it quickly while it is hot. When it is difficult to filter clear syrup, filter paper pulp, talcum powder, chicken egg protein and other filter AIDS can be used to adsorb impurities, which is helpful for filtering. Plate-and-frame filter press can be used for filtration in mass production.
This method is suitable for simple syrup or syrup containing non-volatile components and drugs with stable heating.
Cold dissolving method: Weigh sucrose according to the prescription, dissolve it in distilled water or drug-containing solution under stirring at normal temperature (about 200C), filter it until it is clean, and collect it.
The advantage of this method is that the finished product is light in color and contains less invert sugar. The disadvantage is that sugar takes a long time to dissolve, so the preparation should strictly require environmental hygiene and personal hygiene to prevent bacterial contamination.
This method is also applicable to simple syrup and syrup that is not suitable for heating, such as syrup containing volatile oil and volatile drugs.
Mixing method: the concentrated solution of leaching preparation, medicine or liquid preparation of medicine and syrup are mixed directly and evenly in this legal system.
The water-soluble solid medicine can be made into concentrated solution with a small amount of distilled water and then mixed with the calculated amount of single syrup. If the solubility in water is small, it can be obtained by adding appropriate auxiliary solvent to dissolve it and then mixing it with the calculated amount of single syrup.
Liquid medicine, such as glycerol, can be directly mix with calculated amount of simple syrup. Such as volatile oil, can be dissolved in a small amount of ethanol and other auxiliary solvents or appropriate solubilizers, and then mixed with single syrup.
When tincture and fluid extract are mixed with single syrup, appropriate amount of glycerol or other suitable stabilizers or appropriate filter AIDS can be added for filtration.
The water-soaked preparation is prone to fermentation and mildew because it contains protein, mucilage, etc. It can be heated to boiling for 5 minutes, then coagulated and filtered, and the filtrate is evenly mixed with single syrup. If necessary, the concentrate of the leachate can be treated with concentrated ethanol once, and the mother liquor after recovering ethanol is added into the single syrup and evenly mixed.
If the medicine is a dry extract of traditional Chinese medicine, it should be pulverized into fine powder, then added with glycerin or other suitable diluents, ground in a sterile mortar and then mixed with single syrup to get the final product.