Preparations of plant drugs made with alcohol cannot contain albumin since it is insoluble. Fixed oils, fats, and waxes are salts formed by acids (oleic, palmitic, stearic) with glyceryl. When a strong alkali like potassium or sodium hydroxide is added to these substances, soap forms. Olive oil and almond oil consist largely of olein. Fixed oils have no action on vital organs but soften the skin for medicinal agents application. Organic acids in fruits lack medicinal value unless they are resin-acids. Tannins, found abundantly in plants, are astringent and used to tan leather or form insoluble compounds with other substances. Volatile oils, despite their misleading name, are less volatile than water and have powerful odors due to oxygen compounds. Resins are oxidation products of volatile oils, often used industrially for varnishes and sealing wax. Glucosides decompose into sugar upon contact with water or specific ferments. <Callout type="important" title="Key Property">Fixed oils cannot be distilled but burn with a smoky flame if oxygen is insufficient.</Callout> Tannins form insoluble compounds with gelatin, mucilage, and metallic salts. Volatile oils are stimulants and diuretics, often used in spices.
Key Takeaways
- Fixed oils are salts formed by acids and glyceryl, used in soap making.
- Tannins form insoluble compounds with other substances and have astringent properties.
- Volatile oils are stimulants and diuretics, often containing oxygen compounds for strong odors.
Practical Tips
- Use diluted alcohol to prevent tannin precipitation in preparations.
- Extract fixed oils using ether before making solid extracts.
- Add glycerin to volatile oil preparations to maintain stability.
Warnings & Risks
- Avoid overexposure to volatile oils as they can irritate the skin and respiratory system.
- Resins may cause blistering when applied externally due to their acrid nature.
Modern Application
While this chapter focuses on historical pharmaceutical practices, understanding plant constituents remains crucial for modern survival preparedness. Knowledge of tannins, volatile oils, resins, and glucosides can aid in natural remedy creation and preservation techniques.
Frequently Asked Questions
Q: What are the main acids that form fixed oils?
The principal acids forming fixed oils include oleic acid, palmitic acid, and stearic acid.
Q: Why is glycerin added to volatile oil preparations?
Glycerin prevents precipitation of compounds insoluble in water or alcohol by making them soluble.
Q: What are the properties of tannins when extracted from plants?
Tannins, when separated from other substances, form a dry solid that is light yellow, soft, friable, and soluble in water, alcohol, and glycerin.