Introduction to Pharmacognosy, Carbohydrates, Glycosides, and Tannins – Lecture Notes (Module 1–3)

A comprehensive set of Q&A flashcards covering pharmacognosy basics, plant constituents, carbohydrate chemistry, glycosides and their biosynthesis, and tannins as presented in the notes.

What is the meaning and origin of the word pharmacognosy?

From Greek pharmakon (drug) and gnōsis (knowledge); literally, knowledge of drugs.

How is pharmacognosy defined as an applied science?

It deals with the biological, chemical, and economic aspects of natural drugs and their constituents.

What was Flückiger’s comprehensive view of pharmacognosy?

It is the simultaneous application of various scientific disciplines to acquire knowledge of drugs from every point of view.

What are the two main branches connected to plant constituents in pharmacognosy and phytochemistry?

Plant Chemistry (study of plant constituents and biosynthesis) and Phytochemistry (study of composition, extraction, biosynthesis, and identification of plant principles).

Who is regarded as the father of modern Plant Chemistry?

Scheele.

What is Materia Medica?

Ancient medical knowledge about drugs; the term means medical matter.

What is De Materia Medica and who wrote it?

A famous five-volume treatise on drugs written by Pedanios Dioscorides; described about 600 plant drugs and remained authoritative for centuries.

Who coined the word pharmacognosy and where is it found?

J.A. Schmidt in Lehrbuch der Materia Medica.

Who is called the father of Galenical Pharmacy?

Galen.

Which three disciplines defined the drug sciences in the late 19th century?

Pharmacology (drug actions), Pharmacognosy (drug information from natural sources), Medicinal Chemistry (synthetic drugs).

What are crude drugs?

Vegetable/animal drugs consisting of natural substances that have undergone only collection and drying (little to no processing).

How are natural substances categorized in the notes?

1) Whole plants and herbs and their parts; 2) Whole animals and parts; 3) Substances with no molecular changes from nature.

What are plant metabolites and their two main groups?

Plant metabolites are: 1) Primary metabolites (CHON, CHO, lipids) and 2) Secondary metabolites (alkaloids, steroids, flavonoids, etc.).

What are the two main groups of plant constituents according to the notes?

Active constituents (therapeutic) and inert constituents (no definite pharmacologic activity).

What role do extraction methods like maceration, infusion, and percolation play in pharmacognosy?

They are classical methods used to extract active constituents from crude drugs.

Name common solvents used for extraction and their targets.

Petroleum ether (fats, oils, waxes); ether/chloroform (alkaloids, resins); 95% ethanol (glycosides, tannins, resins); 80% ethanol (similar targets, phytochemical screening); water (glycosides, sugars, salts, gums); acids/bases (alkaloids and polysaccharides).

What is a monosaccharide, disaccharide, trisaccharide, and tetrasaccharide?

Monosaccharides: single sugar units; Disaccharides: two monosaccharides; Trisaccharides: three monosaccharides; Tetrasaccharides: four monosaccharides.

What are the common hexoses and how are they classified?

Hexoses are monosaccharides with six carbons; classified as aldoses (e.g., glucose, mannose, galactose) and ketoses (e.g., fructose, sorbose).

Give examples of disaccharides and what they yield upon hydrolysis.

Sucrose (glucose + fructose), Maltose (glucose + glucose), Lactose (glucose + galactose).

What are glycosides?

Compounds in which a sugar (glycone) is bonded to a non-sugar moiety (aglycone) via a glycosidic bond.

What are the glycone and aglycone parts of a glycoside called?

Glycone is the sugar part; aglycone (or genin) is the non-sugar portion.

What are the four types of glycosides by glycosidic linkage?

O-glycosides, N-glycosides, S-glycosides, and C-glycosides.

What is an O-glycoside?

A glycoside where the sugar is linked to the aglycone via an oxygen (–OH) linkage; e.g., Rhein-8-glucoside from rhubarb.

What is an N-glycoside?

A glycoside where the sugar is linked to the nitrogen of the aglycone (nucleosides).

What is a S-glycoside?

A glycoside where the sugar is linked to sulfur (thio-glycosides); e.g., Sinigrin from black mustard.

What is a C-glycoside?

A glycoside where the sugar is directly attached to a carbon atom of the aglycone; e.g., Aloin (Barbaloin) from Aloe.

How are glycosides biosynthesized in plants?

Sugar phosphates form UDP-sugar; uridine diphosphate sugar (UDP-sugar) reacts with the aglycone via glycosyl transferase to form glycosides; additional sugars can be added in subsequent steps.

What is an anthracene glycoside?

A glycoside where the aglycone is an anthraquinone/anthrone/anthracene derivative; reduced anthraquinones are generally more active.

What are saponin glycosides?

Glycosides that foams and have surface-tension–altering properties; include steroidal and triterpenoid sapogenins; Diosgenin is a key steroidal sapogenin.

What are cyanogenic glycosides and give examples?

Glycosides that yield hydrocyanic acid on hydrolysis; examples include dhurrin and prunasin.

What are isothiocyanate glycosides?

Glycosides (glucosinolates) that yield isothiocyanate upon hydrolysis; examples: sinigrin, sinalbin, gluconapin.

What are flavone glycosides?

Glycosides with flavone-based aglycones (flavones, flavonols, flavanones, etc.); examples include rutin, quercitrin, hesperidin, diosmin, vitexin.

What are coumarin and furanocoumarin glycosides?

Glycosides with a coumarin aglycone; furanocoumarins contain a furan ring and are often toxic; biosynthesis involves shikimate and polyketide pathways.

What are aldehyde glycosides and give examples?

Glycosides where the aglycone is an aldehyde; e.g., glucovanillin in vanilla and cinnamic aldehyde in cinnamon.

What are phenol glycosides?

Glycosides whose aglycones are phenolic; examples include Salicin (willow bark), arbutin (bearberry), phloridzin, and others in a table of examples.

What is a bitter/miscellaneous glycoside?

A class of glycosides that play roles in digestion as stomachics and bitter tonics; they contribute to bitterness and digestive stimulation.

What are hydrolysable tannins?

Tannins that hydrolyze under acidic or enzymatic conditions to phenolic acids (gallic, ellagic) bound to glucose; include gallotannins and ellagitannins.

What are condensed tannins (proanthocyanidins)?

High-molecular-weight tannins that are not readily hydrolyzed; formed from flavonoid units (catechin, leucoanthocyanidin) and can polymerize to give phlobaphens.

What are true tannins vs pseudotannins?

True tannins give a positive Goldbeater’s skin tanning test; pseudotannins are lower molecular weight phenolics that do not fully react in the test.

What are the main characteristics of tannins?

Colloidal, non-crystalline; soluble in water (and some alcohols) but mostly insoluble in organic solvents; molecular weight 500–>20,000; can bind proteins.

What biosynthetic pathway is common to tannins and many other phenolics?

The phenylpropanoid/ shikimic acid pathway.

What are the two main tannin categories and their formation?

Hydrolysable tannins from gallic/ellagic acids attached to glucose; condensed tannins (proanthocyanidins) from flavonoid units like catechin.

What is the common sugar-derived core for hydrolysable tannins?

A glucose core with ester-linked phenolic acids (gallic or ellagic acids).

What is the role of proanthocyanidins in plants and nutrition?

Form from leucocyanidins; related to flavonoids; contribute to astringency and can affect nutrition; polymerize to give colored products.

What is the role of tannins in animal nutrition?

Tannins can affect protein availability and digestion; common focus is their binding properties and potential anti-nutritional effects.

What is the main structural feature of glycosides in terms of linkage basis?

Linkage can be O-, N-, S-, or C-glycosidic depending on the atom through which sugar attaches to the aglycone.

What is a key example of an N-glycoside?

Adenosine (nucleoside) as an example of an N-glycoside.

What is a key example of an S-glycoside?

Sinigrin from black mustard (Brassica juncea), an isothiocyanate glycoside variant.

What is a key example of a C-glycoside?

Aloin (Barbaloin) from Aloe; a glycoside where sugar is directly attached to carbon of the aglycone.

What is the general difference between hydrolysis products and glycosides?

Hydrolysis breaks glycosidic bonds to yield sugar(s) (glycone) and aglycone; often used to identify glycoside types.

What is the main route for glycoside biosynthesis from UDP-sugars?

Glycosyl transferase transfers the sugar from UDP-sugar to the acceptor, forming the glycoside.

What are the two major groups of plant constituents involved in pharmacognosy?

Active constituents (therapeutic) and inert constituents (no definite pharmacologic activity).

What is the photosynthesis equation as summarized in the notes?

2H2O + CO2 + light → (CH2O) + H2O + O2 (plus corresponding energy carriers).

What is the significance of the shikimic acid pathway in glycoside biosynthesis?

Shikimic acid pathway provides the carbon skeletons for phenylpropanoid-derived glycosides (e.g., coumarins, flavonoids) and cyanogenic glycosides.

What are the three historical figures mentioned in pharmacognosy history pages and their contributions?

Galen (Galenical pharmacy), Pedanios Dioscorides (De Materia Medica), J.A. Schmidt (coined the word pharmacognosy).

What is the main difference between primary and secondary plant metabolites in terms of value and occurrence?

Primary metabolites are abundant and essential; secondary metabolites are unique to species and often have therapeutic value.

What is a glycoside’s aglycone called and what is its solubility preference?

Aglycone (genin) is typically soluble in organic solvents; glycone (sugar) is soluble in water.

What is the difference between hydrolyzable and nonhydrolysable tannins?

Hydrolyzable tannins hydrolyze to phenolic acids bound to glucose; nonhydrolysable tannins (condensed tannins) do not readily hydrolyze.

Name two important classes of tannins and one example each.

Hydrolysable tannins (gallic/ellagic acids; e.g., gallotannins) and condensed tannins (proanthocyanidins; e.g., catechin-derived polymers).