These free B.Pharm notes on evaluation of crude drugs cover chapter 13 of Introduction to Pharmacognosy, a first-semester subject. Read the key points below, then study the complete chapter PDF. You can browse every chapter in the Introduction to Pharmacognosy category.
Table of Contents
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Overview of evaluation of crude drugs
This chapter explains how crude drugs are tested to confirm identity, quality and purity and to detect adulteration. It covers organoleptic, microscopic (qualitative and quantitative), chemical and biological evaluation, including histochemical tests, trichomes, stomata, stomatal index, the Lycopodium spore method, chemical constants, chromatography and bioassays.
Key points on evaluation of crude drugs
- Evaluation means testing a drug to confirm its identity, decide its quality and purity, and detect adulteration, and sensory and microscopic examination is the first step.
- The ocular micrometer has no fixed unit, so it must be calibrated against the stage micrometer, and size equals ocular divisions covered multiplied by the calibration factor.
- Stomatal index is S divided by E plus S, multiplied by 100, and it is more reliable than stomatal number because it stays nearly constant whatever the leaf age.
- In the Lycopodium spore method, uniform spores of about 25 micrometres, with about 94,000 per mg, act as a standard to count characteristic particles in powdered drugs.
- Rf value is the distance travelled by the solute divided by the distance travelled by the solvent front, and it is characteristic of a compound under fixed conditions.
Relevance to pharmacy practice
Pharmacists must be sure that a herbal drug is genuine, pure and potent before it reaches a patient. Knowing these evaluation methods helps them judge quality, detect adulteration and understand the standards that herbal products must meet.
Every chapter in this subject builds on the one before it, so do not skip topics that look simple. Definitions, classifications and examples are the parts that examiners return to most often, and a clear understanding here will also make later subjects easier to follow in the coming semesters.
Frequently asked questions on evaluation of crude drugs
What is organoleptic evaluation of a drug?
It is a simple sensory method in which the drug is examined with the sense organs for colour, odour, taste, size, shape and surface. A clear difference from the standard suggests adulteration, deterioration or poor quality.
What is the stomatal index and how is it calculated?
Stomatal index is the percentage of epidermal units that have become stomata, calculated as S divided by (E plus S) multiplied by 100. S is the number of stomata and E the number of epidermal cells.
What is a bioassay?
When the potency of a drug is found by measuring its effect on living organisms, tissues, organs, micro-organisms or cell lines, it is called a bioassay. It confirms activity and therapeutic dose of herbal drugs.
Quick revision checklist
Use this self-test after reading the chapter on evaluation of crude drugs. If you can do all of the following without looking at your notes, you are ready for the exam.
- I can explain: organoleptic evaluation of drugs
- I can explain: calibration of the ocular micrometer
- I can explain: types of trichomes and stomata
- I can explain: the stomatal index and Lycopodium method
- I can explain: chemical constants and chromatography
Study and exam tips
Start by reading the chapter once for the overall idea, then revise evaluation of crude drugs using headings, definitions, classifications and examples. Short-answer questions in the university exam usually ask for definitions, features, advantages, disadvantages and examples, so write these in your own words and practise drawing the tables and flow charts that the chapter has.
For wider reading, standard textbooks and open resources such as the NCBI Bookshelf help you confirm terms and see more examples. Revise evaluation of crude drugs again a day later and again a week later, because spaced revision improves long-term memory.
This page is part of the Introduction to Pharmacognosy series for first-semester B.Pharm students on B.Pharm Guru, where every chapter has a short summary and a full PDF. Bookmark this page and share it with classmates who are preparing for the same exam.
Related notes: 15. BIOLOGICAL METHODS AND DNA BARCODING, 16. PRIMARY AND SECONDARY METABOLITES OF PLANTS.
Next: 14. PHYSICOCHEMICAL PARAMETERS. Back to the Introduction to Pharmacognosy category.
