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GPAT preparation - How to study pharmacognosy?

by egpat        Posted on 08 Jun 2019


Pharmacognosy is one of the scoring subject in GPAT examination. You can get plenty of questions from this subject all being direct and easily answered. There will be no twist in the question, so if you cover the subject thoroughly you can spot the answer perfectly without going to the negative marking. So here we will discuss how you can prepare phramacognosy for getting good score in GPAT and NIPER exams.


Question pattern

How many number of questions come from pharmacognosy? Which type of questions appear in GPAT from this subject?

You will get few of the questions in your mind when you start your GPAT preparation. Yes, it is always better to know the pattern and strategy of question before you start your preparation rather than blindly studying and wasting your time.

Generally you may get 10-25 questions from pharmacognosy in GPAT providing you a chance to get significant score. Of course, the number of questions may vary from year to year but still the figures fall within this region.

You should never mistake about the number of questions by counting them from latest GPAT exam. For example, suppose in the last GPAT exam if you found only 10 questions from pharmacognosy giving a score value of 10 x 4=40 marks, you shouldn’t think that pharmacognosy has little value in GPAT. The same may not happen in the next year and the number of questions may raise to even 25-30 providing you a score of at least 25 x 4=100 marks which is highly significant.

So don’t put any doubt in your mind, go on with your great preparation in pharmacognosy and definitely you will get good score from this subject.

Ok, that’s fine that you have realised the value of pharmacognosy in GPAT and ready to start your preparation.

But how to start? Which topics you should study?


These are next questions that peep into your mind. So let’s have a discussion one by one on the topics that you have to study.

Classifications

First of let’s see what the pharmacognosy deals with. This subject includes a number of plant drugs each having their taxonomical classification as well as phytochemical classification. For example, if you see Rauwolfia, it is classified under roots and rhizomes.

rauwolfia plant

At the same time, Rauwolfia is classified under alkaloids with sub category as indole alkaloid. This is the phytochemical classification based on the nature and ring system present in the phytochemicals of the plant.

Rauwolfia as indole alkaloid

Which is more important in GPAT?

Even taxonomical classification is essential, but from examination point of view phytochemical  classification is more important. So you start learning the classification of the plants based on their phytochemistry.

phytochemical classification

From the taxonomy you may get simple questions on part of the plant or its family. For example consider one of the questions asked in previous GPAT exam.

part of plant

But from phytochemical classification you may get plenty of questions few of them are as follows.

Biological sources

Every plant has its biological source which covers three points.

  • Part of the plant
  • Biological name of the plant
  • Family of the plant

So when you study biological sources of plants you can cover all these points and can answer any such type of questions asked in GPAT.  Let’s have few examples of previous GPAT questions on this content.

What is the biological source of Alexandrian Senna?

(A) Cassia aungustifolia

(B) Cassia acutifolia

(C) Cassia Bravifolia

(D) Cassia Nerifolia

This is a simple question from GPAT 2016 and Alexandrian seena is obtained from Cassia acutifolia while Tinnevelly senna is obtained from Cassia aungustifolia.

You can make your preparation very simple, by preparing charts that contain various columns with information like category of the plant name, biological source, important phytochemicals and their uses. This provides you a quick revision and ready reference so that you can learn all these things in a short period with memory lasting for longer days. But you have to study and practice these tables  with regular revision otherwise the concept will be vaporised and erased from your mind.

Chemical tests

How can you know a phytochemical belong to a specific plant? We generally use chemical tests to identify that produce some visible colored reactions. For instance, Presence of alkaloids can be detected by wagner’s test and presence of proteins by ninhydrin test. These are the identification tests for a compound in phytochemical group.

chemical tests

Here is a question from GPAT 2017.

A crude drug powder was heated with ferric chloride, water and concentrated hydrochloric acid followed by extraction with chloroform. The  chloroform layer was  treated with ammonia,  the ammonical layer turned pink. The test indicates presence of which of the following phytoconstitutent?

(A) Anthraquinone-C-glycosides

(B) Flavanones

(C) Cardiac glycosides

(D) Saponin glycosides

Here answer is option A, that is, Anthraquinone-C-glycosides. The given chemical test is a modified Brontrager’s test which is used for detection of C-glycosides. Normally O-glycosides like senna are identified by Brontrager’s test but as C-glycosides are resistant to hydrolysis, they are treated with ferric chloride to bring the hydrolysis.

modified brontrager's test

But many of the times specific chemical tests are more important and will be focussed in GPAT exam. For example we have a list of chemical test each specific to a phytochemical.

You should focus on those specific chemical tests and memorise along with which chemicals used in the test and what the color of the reaction produced.

specific chemical tests

Sometimes color of the reaction is important to distinguish the varieties of the plant. Consider the following question.

Chinese rhapontic rhubarb can be distinguished from Indian rhubarb by fluorescence developed in UV light which is:

(A) Deep yellow

(B) Deep violet

(C) Green

(D) Blue

Chinese rhubarb gives blue fluorescence while Indian rhubarb give deep violet fluorescence when irradiated with UV light. So here the test is same for both but color produced is different. You should catch such type of point of differences where there is a high chance to get a question in GPAT. You can prepare a mnemonic to remember such points very easily. For example, here you can remember IDV which indicates that Indian à Deep Violet.

fluorescence by rhubarb

You can design you own codes according to our ease so that your memory lasts for longer period without any ambiguity.

Phytochemistry

Recently we can observe more number of questions from phytochemistry of the plants. Consider the following question.

Atropa belladonna mainly contains

(A) Henbane

(B) Hyoscyamine

(C) Benztropine

(D) Cocaine

This is a basic level question and if you prepare tables of classification, you can easily identify hyoscyamine as the answer.

Let’s go somewhat deep into the concept. Consider one of the previous GPAT question here.

(-) – Hyoscyamine is 

(A) 15-20 times more active as a mydriatic than (+)- hyoscyamine 

(B) Inactive as a mydriatic 

(C) 3-5 times less active as a mydriatic than (+)- hyoscyamine 

(D) 100 times more active as a mydriatic than (+)- hyoscyamine

This is an advanced level question. Here we know that belladonna contains both l and d-hyoscamine but here question is on the point that which is more active? So you have to study more on phytochemistry.

Among all the tropane alkaloids levo form is more active and here (+)- hyoscyamine  is 15-20 times more active as a mydriatic than (+)- hyoscyamine. So the answer is option A.

 

Differences between variants

Many of the times you may get questions on how you can differentiate the different varieties of the plant.

For example, senna is obtained from many varieties of the plant. Among them one is Alexandrian senna and another one is Tinnevelly senna. Both varieties of the plants differ in their biological source as well as location. Alexandrian senna is obtained from dried leaves of Cassia acutifolia while Tinnevelly senna is from dried leaves of Cassia angustifolia.

OK, fine. But if you have both of the leaves in your hand, can you differentiate them? Yes, of course, by using quantitative microscopy you can identify which variety it is. Alexandrian senna has higher Vein-islet number and lower stomatal index than Tinnevelly senna.

Senna-varieties

In this way list out the major differences in the varieties by which we can differentiate them clearly.

Difference in the chemical nature

Plants can have phytochemicals which can differ in the solubility and exist as different extracts. For example, plants may have water-soluble fractions, water-insoluble fraction, ether soluble fractions etc. You have to focus on these points as there is a lot of chance for getting questions in GPAT.

Let's go with one previous GPAT question.

Read the given statements about the constituents of Shellac:

[P] : Shellolic acid, a major component of alicyclic fraction is responsible for colour.

[Q]: Shellolic acid, a major component of   aromatic fraction is responsible for colour.

[R] : Shellolic acid is a major component of aliphatic fraction and laccaic acid is a component of aromatic fraction.

[S] : Aliphatic components are shellolic acid which is alicyclic and aleuratic acid which is acyclic, while laccaic acid is an aromatic colouring principle.

What is the correct combination of options?

(A) P is true; Q is true; R is true; S is true

(B) P is false; Q is false; R is false; S is true

(C) P is false; Q is false; R is true; S is true

(D) P is true; Q is false; R is false; S is true

This is one of the advanced level questions. Even the question is so much elaborative, still you can easily spot the answer if you know right information.

Fractions in shellac

Shellac mainly consists of two fractions aliphatic fraction and aromatic fraction with components as follows.

  • Aliphatic fraction
    • Alicyclic fraction – Shelloic acid
    • Acyclic fraction - aleuretic acid
  • Aromatic fraction – Laccaic acid

So, if you know the right information you can easily spot the answer have an advantage over competitors.

Conclusion

That's all about various questions from cognosy in GPAT. Still lot of questions appear from pharmacognosy which are direct and on fundamental concepts. So pharmacognosy is one of the scoring area in GPAT and you should get good benefit by attempting maximum number of questions. But keep in mind that few questions from this subject may be of very advanced and research level. Sometime they may be out of your b.pharm syllabus. You shouldn't worry about such questions and if you are not confident about right answer, just leave them to avoid negative marking. Apart from one or two such questions, you can score well from plenty of questions from pharmacognosy in GPAT. Only the requirement here is that you have to study thoroughly and practice well. Try to revise many times to get a storng grip on the concept. If you like don't forget to share this post with your friends. Wishing you all the best for forthcoming GPAT, have a great day !





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