exists also in peach kernels, cherry seeds and a number of other seeds, which are therefore poisonous. They do not contain any poison, but they contain the glucoside amygdalin, which gives rise to the formation of the highly poisonous hydrocyanic acid as soon as wetted with water. No general description of glucosides beyond what little has already been mentioned can be made, because they are so miscellaneous in character. Some of them are soluble in water, but not in alcohol, while others are soluble in alcohol, but not in water. A large number of the glucosides are either poisonous or form poisons when decomposed. In fact, two-thirds of all poisonous plant drugs contain alkaloids, and the remaining one-third contain glucosides. <Callout type="important" title="Important">Understanding these compounds is crucial for identifying potentially dangerous plants.</Callout> Many of the glucosides contained in drugs have a decided action on the circulatory system, affecting the heart strongly. Tinctures and fluid extracts are made of drugs containing glucosides, but solid extracts are not made of all glucosidal drugs, because of the unstable character of the glucosides.
Alkaloids are chemical compounds containing carbon, hydrogen and nitrogen, or carbon, hydrogen, nitrogen and oxygen, having the power of neutralizing acids to form salts and of turning certain red vegetable colors blue. They are called alkaloids because they resemble the alkalies in the properties just mentioned. They are also called vegetable bases. When the alkaloids form salts with acids they act in the same manner as ammonia, in that the entire molecule of the alkaloid enters into combination with the entire molecule of the acid by a rearrangement of the atomic linking. When ammonia, H3N, reacts with hydrogen chloride, HC1, the compound formed is H4NC1, from which it will be seen that the hydrogen and the chlorine of the hydrogen chloride are separated from each other by the nitrogen of the ammonia. When ammonia reacts with nitric acid in ammonium nitrate, H4NN03, it will also be seen that the nitrogen of the ammonia separates the hydrogen of the nitric acid from its N03. Alkaloids and acids form salts in a similar way. For this reason alkaloids have sometimes been called compound ammonias. <Callout type="risk" title="Risk">Ingesting large amounts of alkaloids can be fatal.</Callout> Alkaloids are always poisonous, and some of them are so potent that the customary dose may be less than the two-hundredth part of a grain. Examples of alkaloids are found in quinine, morphine, strychnine, cocaine and caffeine. It is true that quinine and caffeine and some other alkaloids are not generally looked upon as being poisonous, but if a considerable quantity be taken internally of either of them, alarming effects will undoubtedly be produced.
From what has been said, it will be apparent that a very large number of our most important plant drugs contain alkaloids as their principal active constituents. The English names of alkaloids are in this country given the ending ine, and the corresponding Latinic titles in the pharmacopoeias have the ending ina. There are two classes of alkaloids — the ternary alkaloids and the quaternary alkaloids. <Callout type="tip" title="Tip">Ternary alkaloids are volatile and often liquid, while quaternary ones are solids.</Callout> The ternary alkaloids are called so because they contain only the three elements carbon, hydrogen and nitrogen. They are volatile, so that they can be distilled or vaporized without decomposition, have a strong odor and are generally liquid. The quaternary alkaloids are called so because they contain four elements, carbon, hydrogen, nitrogen and oxygen. These are solids. Very few of them can be vaporized without decomposition, and they have no odor. The volatile alkaloids are few in number in comparison with the solid alkaloids. The volatile alkaloids are soluble in water as well as in alcohol, and hence preparations of plant drugs containing volatile alkaloids may be made either with alcohol or water, or a mixture of the two. But the alkaloids containing oxygen usually require a strongly alcoholic menstruum, because they are rarely soluble in water.
Alkaloids seldom occur in the plants and plant drugs uncombined with acids. They are usually found in combination with peculiar organic acids which, like the alkaloids themselves, are rarely found in more than one plant genus. The salts which the alkaloids form with the organic acids referred to are generally alcohol-soluble, and to a much less extent water-soluble. But the alkaloids can be extracted from the plant drugs and separated from all other substances and then converted into salts with the ordinary acids. These salts are frequently freely water-soluble.
From what has been said it will be understood that the alkaloids of plant drugs may be extracted with water to which has been added some acid forming a water-soluble salt with the particular alkaloid to be dissolved, or the drug may be mixed with an alkali which liberates the alkaloid from its natural salt, after which alcohol, ether, chloroform, petroleum spirit or some other suitable solvent for the free alkaloid may be used. But these are chemical methods of extracting alkaloids. The pharmaceutical method of extracting them consists in using an alcoholic menstruum which will extract the natural alkaloidal compound without chemical alteration.
The active principles of plant drugs belong to the classes described as tannins, bitters, volatile oils, resins, glucosides and alkaloids, and any plant drug containing no substance belonging to either of those classes is not likely to possess any medicinal value. The activity of any particular drug may be due to only one substance or it may be due to two or three or several substances.
The chemical constituents found in plant drugs are generally formed in the plant during its life, but several important valuable constituents of drugs are formed after the death of the plant, by chemical changes in the natural constituents. Opium, for instance, is a drug formed by drying the fluid that exudes from poppy capsules when full grown and just before they ripen, through incisions made in the capsules. No morphine or only traces of it or of any other alkaloids have been found in the poppy capsules, but the opium, when finished by drying the poppy juice in the sun, may contain over 20 per cent, of total alkaloids.
Another illustration is furnished by the common drug called frangula, which, when just gathered, is a violent griping cathartic and even emetic, but which after having been kept for a year or two becomes a mild laxative, the cathartic substances being decomposed and giving place to decomposition products having a milder action. Some drugs are used in the fresh condition before the natural constituents undergo alteration, while other drugs are not used until after they have become modified by the chemical changes referred to. It is further to be understood that these chemical changes in the constituents of drugs continue through a long time, so that probably all plant drugs deteriorate when kept too long, and many of the plant drugs contain such unstable active principles that they cannot be preserved unaltered even for a few months.
A fresh supply of an unstable plant drug can, of course, be obtained only once a year, and such drugs should accordingly be procured by the pharmacist at the right season, that is, immediately after the new crop comes into the market. Such drugs should be preserved with the greatest care. Very few drugs are comparatively permanent, so that they remain in good condition as long as two years.
Test Questions 1. What is a carbohydrate? 2. Which of the class of carbohydrates are water-soluble? 3. What is exosmosis? 4. What advantage can be taken of dialyzation in the extraction of the constituents of drugs? 5. Which of several classes of chemical constituents of drugs are dialyzable? 6. Name a solvent for starch in its normal condition. 7. What is meant in pharmacy by the expression 'altered starch'? 8. What kinds of drugs are employed for making demulcent decoctions and what drugs for mucilaginous infusions? 9. Name some substances containing normal starch and some other substances containing altered starch. 10. What kind of a menstruum can be used on plant drugs which will not extract carbohydrates? 11. What is the cause of gelatinization in certain liquid pharmaceutical preparations? 12. What is a gum? 13. Name all of the gums you can think of. 14. What is the difference between arabin and bassorin? 15. Can you name some gums soluble in alcohol? 16. If you have a liquid extract containing mucilage in solution, how can you remove that mucilage from the liquid? 17. What are the pharmaceutical uses of the official gums? 18. In what parts of plants is physiological mucilage usually found? 19. In view of the fact that mucilage ferments so easily, how can drugs containing mucilage be preserved? 20. In what manner does sugar act as a preservative of water-solutions of fermentable substances? 21. What are the pharmaceutical uses of sugar? 22. What proportion of alcohol must be contained in a solution of fermentable matter in order to prevent fermentation? 23. Mention some plant constituents contained in aqueous liquid extracts which are not contained in alcoholic liquid extracts. 24. Name some plant constituents contained in alcoholic liquid extracts which are not contained in aqueous extracts. 25. Name some plant constituents which are soluble both in water and in alcohol. 26. At what temperature does starch become pasty in water? 27. At what temperature does albumin coagulate? 28. Which kind of a liquid extract contains the most albumin, a liquid extract-made with cold water or with boiling water or with alcohol? 29. Which preparation contains the most starch, one made with cold water, boiling water or alcohol? 30. Can albumin in solution be separated from a liquid extract? If so, how? 31. What is glyceryl hydroxide commonly called? 32. Can you mention any other common glyceryl compounds? 33. What is hard soap and what is soft soap? 34. Name the most common fat-acids. 35. What is the chemical composition of olive oil, lard, tallow and cottonseed oil? 36. What is stearin? 37. What are the principal physical differences between olein, palmitin and stearin? 38. What liquid pharmaceutical preparations are most liable to contain fixed oils, those made with water, with diluted alcohol, with strong alcohol or with ether? 39. What are the pharmaceutical and medicinal uses of fixed oils? 40. What parts of plants contain fixed oil more frequently than other plant parts? 41. Can a solid extract be made from a plant drug containing fixed oil without obtaining a product mixed with grease? If so, how? 42. What are the best solvents for fixed oils? 43. What is tannin? 44. What are its most characteristic properties? 45. Name three different solvents for tannin. 46. What is the most notable difference between physiological tannin and pathological tannin? 47. What kinds of fluid extracts and tinctures are most liable to contain precipitates formed on standing? 48. What is meant by an amarum? 49. What menstruum is commonly employed in making tinctures of drugs containing amara? 50. What menstruum is commonly employed in making fluid extracts of drugs containing volatile oils? 51. What menstruum is commonly employed in making fluid extracts of drugs containing tannin? 52. Enumerate the differences you can think of between volatile oils and fixed oils. 53. How would you make a solid extract of a drug containing volatile oil as its only active constituent? 54. What are the most common constituents of volatile oils? 55. Do you think you can discover tannin in a plant drug without a chemical examination of it? 56. Do you think you can discover volatile oil in a plant drug without separating the volatile oil or detecting it by chemical means? 57. What is the difference between a carbohydrate and a hydrocarbon? 58. What volatile oils have the strongest odors? 59. What is the general physiological and therapeutic action of volatile oils? 60. What volatile oils produce a grease spot on clean white unsized paper? 61. What are the best solvents for volatile oils? 62. What are volatile oils liable to contain besides hydrocarbons and camphors? 63. What are the constituents contained in aromatic astringents; in astringent bitters; in aromatic bitters? 64. By what means can you detect alcohol in a volatile oil adulterated with that liquid? 65. What are the solutions of volatile oils in water called? 316 A CORRESPONDENCE COURSE IN PHARMACY 66. Why are resins usually found together with volatile oils in plants? 67. What are the differences between gums and resins? 68. What are the pharmaceutical uses of inert resins? 69. What are the medicinal effects most common in resins and resin compounds? Why does potash lye dissolve resin? 70. Bitter almond is the source of expressed oil of almond, as well as of volatile oil of bitter almond and amygdalin. The amygdalin is soluble both in hot alcohol and in water. Wrhat is the best way to extract the amygdalin from the bitter almond? What is amygdalin? 71. How can you separate the fixed oil of bitter almond without having that fixed oil contaminated with amygdalin? 72. How can you make volatile oil of bitter almond and subsequently also amygdalin out of the same lot of bitter almonds? 73. What are usually the active constituents of poisonous plant drugs? What makes peach kernels poisonous? 74. What differences can you mention in the chemical properties of glucosides and alkaloids? 75. Give the origin of the words glucoside and alkaloid. 76. In what respects do the alkaloids resemble ammonia? 77. What is the difference between a ternary alkaloid and a quaternary alkaloid? 78. Are any alkaloids in the free state water-soluble? 79. What class of alkaloids are alcohol-soluble? 80. What are the best solvents for making liquid extracts of alkaloidal drugs? 81. What are the most common chemical processes of extraction of alkaloids from drugs? 82. In what form do the alkaloids usually occur in plant drugs? How long should plant drugs be kept before they are used?
LESSON TWENTY IX Pharmaceutical Preparations -512. The materials out of which pharmaceutical preparations are made may be definite chemical compounds or simple elements, or they may be mixtures of two or more substances. Chemical preparations are those made by processes resulting in the formation of new substances, or, in other words, processes involving chemical reactions. Galenical preparations are preparations made by processes not involving any chemical changes. The Galenical preparations may be simply mechanical mixtures of the ingredients, or they may be solutions or extracts. Organic drugs are of such a complex character that their pharmacy is much less simple than that of definite chemical compounds. The Galenical preparations of plant drugs generally take the form of liquid or solid extracts, the object being to present the medicinal constituents of the drug in the most concentrated and convenient form.
The classification of pharmaceutical preparations may be based upon various considerations. Probably the most practical and convenient classification is the following:
Dry and semi-solid preparations for internal use, made by processes not involving extraction. These preparations include species, powders, triturations, confections and electuaries, masses, troches and pills.
Dry and semi-solid preparations for external use, including poultices, ointments, cerates, plasters and suppositories.
Liquid preparations for internal use, not made by processes of extraction, including solutions, waters, mucilages, syrups, glycerites, mixtures, emulsions and spirits.
Liquid preparations for external use, including lotions, gargles, injections, liniments, etc.
Liquid extracts, including infusions, decoctions, vinegars, tinctures, wines and fluid extracts.
Solid and semi-solid preparations made by processes of extraction, including solid-extracts, oleoresins and precipitated resins.
Key Takeaways
- Understanding the chemical components of plant drugs is crucial for identifying potentially dangerous plants.
- Alkaloids are always poisonous and can be found in various forms, including volatile and solid.
- Tannins play a significant role in preserving plant drugs but can also cause fermentation if not properly managed.
Practical Tips
- Always test the potency of plant drugs before using them to avoid accidental poisoning from alkaloids.
- Store plant drugs in their natural state or under controlled conditions to prevent decomposition and loss of efficacy.
- Use appropriate solvents when extracting active principles from plant drugs, as different compounds require specific methods.
Warnings & Risks
- Large quantities of alkaloids can be fatal, so use them with extreme caution.
- Be aware that some plant drugs may contain dangerous levels of glucosides, such as amygdalin in bitter almonds.
- Incorrect storage or handling of tannins can lead to fermentation and spoilage.
Modern Application
While the historical techniques described in this chapter are rooted in traditional pharmacy practices, many of the principles still apply today. Understanding the chemical constituents of plant drugs is crucial for modern survival medicine, especially when dealing with natural remedies or emergency situations where synthetic alternatives may not be available.
Frequently Asked Questions
Q: What are glucosides and how do they differ from alkaloids?
Glucosides are compounds that contain a sugar molecule (glucose) bound to another non-sugar component. They can form hydrocyanic acid when wetted with water, making them potentially dangerous. Alkaloids, on the other hand, are chemical compounds containing carbon, hydrogen, and nitrogen or oxygen, which have the ability to neutralize acids and turn certain vegetable colors blue. Both glucosides and alkaloids play significant roles in plant drugs but differ in their chemical structure and properties.
Q: How can one safely extract volatile oils from bitter almonds without contaminating them with amygdalin?
To safely extract volatile oils from bitter almonds without contaminating them with amygdalin, you should first separate the fixed oil using a solvent like petroleum ether. Then, you can extract the volatile oil by distillation or other suitable methods. This ensures that the extracted volatile oil remains pure and free of amygdalin.
Q: What are some common solvents for extracting tannins from plant drugs?
Tannins can be extracted using solvents such as alcohol, ether, or chloroform. These solvents effectively dissolve tannins without causing significant chemical changes to the compound. However, it's important to use appropriate safety measures when handling these solvents.
Q: Why are plant drugs often stored in their natural state or under controlled conditions?
Plant drugs are often stored in their natural state or under controlled conditions to prevent decomposition and loss of efficacy. This is because many active principles in plant drugs can deteriorate over time, especially when exposed to moisture, heat, or light. Proper storage ensures that the medicinal value of the drug remains intact until it's needed.
Q: What are some common signs of tannin presence in a plant drug?
Tannins can be identified by their ability to form precipitates with proteins, such as albumin. They also impart astringent properties and can cause the solution to become cloudy or gelatinous when mixed with water. However, these tests are not definitive without chemical analysis.