Indole and Imidazole Alkaloids
Session 24: Indole and Imidazole Alkaloids
Total Session Time: 120 minutes
Prerequisites
Learning Tasks
By the end of this session students are expected to be able to:
Resources Needed:
SESSION OVERVIEW
|Step |Time |Activity/ |Content |
| | |Method | |
|1 |05 minutes |Presentation |Introduction, Learning Tasks |
|2 |15 minutes |Presentation |Natural Sources and Uses of |
| | | |Pilocarpus |
|3 |15 minutes |Presentation |Natural Source and Uses of Vinca |
| | |Buzzing |Alkaloids |
|4 |15 minutes |Presentation |Natural Source and Uses of Ergot |
| | | |Alkaloids |
|5 |15 minutes |Presentation |Natural Source and Uses of Nux |
| | | |Vomica |
|6 |15 minutes |Presentation |Natural Source and Uses of Calabar|
| | | |Beans |
|7 |15 minutes |Presentation |Natural Source and Uses of |
| | | |Rauwolfia |
|8 |15 minutes |Presentation |Natural Source and Uses of Yohimbe|
| | | |Bark |
|9 |05 minutes |Presentation |Key Points |
|10 |05 minutes |Presentation |Evaluation |
SESSION CONTENTS
STEP 1: Presentation of Session Title and Learning Tasks (5 minutes)
READ or ASK students to read the learning tasks and clarify
ASK students if they have any questions before continuing.
STEP 2: Natural Sources and Uses of Pilocarpus (15 minutes)
o Pilocarpus consists of imidazole alkaloids obtained from leaves of
closely related species of Pilocarpus jaborandi and other species of
the genus Pilocarpus, family Rutaceae
o It is also known as Jaborandi
o Pilocarpine
o Isopilocarpine
o Pilocarpidine
o Pilosine
o Pseudopilocarpine
o Isopilosine
o Used in form of Pilocarpine Hydrochloride
o It is a physiological antagonist of Atropine
o Used in ophthalmic practices e.g. treatment of glaucoma
o Causes contraction of pupil of the eye
STEP 3: Natural Source and Uses of Vinca Alkaloids (15 minutes)
o Vinca alkaloids are oncolytic indoline alkaloids obtained from dried
whole plant of Catharanthus roseus, family Apocynaceae
o Leurocristine (vincristine)
o Vincaleukoblastine (vinblastine)
by microbial N-demethylation using Streptomyces albogriseolus
|Activity: Buzzing (5 minutes) |
| |
|ASK students to pair up and buzz on the following question for 2 |
|minutes |
| |
|What are uses of Vinca Alkaloids? |
| |
|ALLOW few pairs to respond and let other pairs to add on points |
|not mentioned |
| |
|WRITE their response on the flip chart/board |
| |
|CLARIFY and SUMMARIZE by using the content below |
o Vinblastine – treatment of generalized Hodgkin’s disease, lymphocytic
lymphoma, histiocytic lymphoma, advanced testicular carcinoma, kaposi’s
sarcoma, choriocarcinoma and breast cancer unresponsive to therapy
o Vincristine – treatment of acute lymphocytic leukemia in combination
therapy in Hodgkin’s disease, ymphosarcoma, reticulum cell sarcoma,
neuroblastoma and Wilm’s tumour
STEP 4: Natural Sources and Uses of Ergot Alkaloids (15 minutes)
o Ergot is the dried sclerotium of a fungus Claviceps purpurea, arising
in the ovary of the rye, Secale cereal, family Hypocreaceae
o The sclerotium arises in the ovary of the rye – secale cereale
o Contains water soluble and water insoluble alkaloids
o Water soluble:
o Water insoluble:
o Derivatives of lysergic acid
o Ergometrine is used to control postpartum haemorrhage
o Ergometrine produces oxytocic effects
o Ergotamine and semi-synthetic dihydrohydroxy ergotamine are employed as
specific analgesic for treatment of migraine (caffeine enhances
absorption)
o Lysergic acid derivative, LSD is a psychomimetic (a potent
hallucinogen) controlled under narcotics
STEP 5: Natural Sources and Uses of Nux vomica (15 minutes)
o Nux vomica are dried, ripe seeds of Strychnous nux-vomica, family
Loganiaceae
o The Main indole alkaloids are;
brucine is in the outer layers
isostrychnine
o The drug also contains 3% fixed oils, glycoside – loganin
o It stimulates peristalsis in chronic constipation and is often combined
with cascara and other laxatives
o Bitter stomachich and tonic (increases gastric juice to improve
appetite and digestion)
o Improves the pulse and raises blood pressure
o At higher doses it is a lethal poison
o Brucine is used commercially as an alcohol denaturant (as it is
extremely bitter)
STEP 6: Natural Sources and Uses of Calabar Beans (15 minutes)
o Calabar beans are dried seeds of Physostigma venonosum, family
Leguminosae
o The seeds are extremely hard
o Physostigmine,
o Isophysostigmine,
o Physovenine
o Eserinmine
o Geneserine
o A reversible inhibitor of cholinesterase thus enhancing the effect of
endogenous Acetylcholine
o It is used systematically as an antidote for atropine poisoning and
other anticholinergic drugs
o Used in ophthalmology to contract the pupil, to combat mydriasis
o It is used in the treatment of glaucoma
the aqueous humour
STEP 7: Natural Sources and Uses of Rauwolfia (15 minutes)
o Rauwolfia consist of dried rhizome and roots of Rauwolfia serpentine,
family Apocynaceae
o The drug is commonly known as Indian snake root
o The African rauwolfia consists of dried roots of Rauwolfia vomitoria
widely distributed in tropical Africa
o Major alkaloids are:
o Other Alkaloids include:
o Other constituents:
sugars
o African rauwolfia contains mainly Reserpine and Rescinnamine
o It is used as a centrally acting anti-hypertensive agent (reserpine)
antihypertensive agents due to its major side effect –suicidal
depression
STEP 8: Natural Sources and Uses of Yohimbe Bark (15 minutes)
o Consists of dried bark of Pausinystalia yohimbe (family Rubiaceae)
o Grows in Cameroon
o Chief constituent is Yohimbine
o As an aphrodisiac agent
o Symptomatic treatment of erectly dysfunction
STEP 9: Key Points (5 minutes)
closely related species of Pilocarpus jaborandi and other species of the
genus Pilocarpus
whole plant of Catharanthus roseus
the ovary of the rye, Secale cereal
STEP 10: Evaluation (5 minutes)
References
Trease, G. E., Evans, W. C., & Evans, D. (2009). Trease and Evans
pharmacognosy. London: Saunders.
Joanne Barnes et al (2002), Herbal medicines 3rd Edition: Pharmaceutical
Press
Wallis, T. E. (2005). Textbook of pharmacognosy. New Delhi: CBS.
Robbers, J. E., Speedie, M. K., Tyler, V. E., & Tyler, V. E. (1996).
Pharmacognosy and pharmacobiotechnology. Baltimore: Williams &
Wilkins.
Heinrich, M., Kinghorn, A. D., Maizels, D., Gibbons, S., & Phillipson, J.
Churchill Livingstone/Elsevier.
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