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Pharmacognosy - Plant Chemistry
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Lecture Notes No. 2Pharmacognosy
Part 1
Plant Chemistry
, INTRODUCTION TO PHARMACOGNOSY
Pharmacognosy – knowledge of drugs and pharmaceuticals | Greek: pharmakon (drugs) and gnosis (knowledge)
BRIEF HISTORY
Babylonians – made clay models of man
Egyptians – very apt in the practice of embalming
Greeks
Pedanios Dioscorides – De materia medica libre cinque (five volumes), 600 plants
(Rome) Galen – described the method of preparing formulas containing plant and animal drugs and the term
”Galenical pharmacy” originated (Cold cream – Galen’s cerate)
Germans
C.A. Seydler – coined the term pharmacognosy in his dissertation in 1815 (title: Anaclectica pharmacognosthica)
Fluckiger –most comprehensive definition of pharmacognosy : “simultaneous application of various scientific
disciplines with the object of acquiring knowledge of drugs from every point of view”
J.A. Schmidt – Lerbuch der Materia medica
Pharmacognosy – “an applied science that deals with the biologic, biochemical and economic features of natural drugs and
their constituents that originate in the plant and animal kingdom”
Appropriate Solvents:
General Process of Extraction 1. Fats - Hexane
Removes substances that can be dissolved by the solvent/menstruum 2. Resins - Alcohol
The undissolved portion of the drug is known as the marc 3. Chlorophyll - Acetone
Product of extraction process: Percolate/Extractive 4. Chrysarobin - Hot benzene
Crude Drugs – undergone only collection and drying
Natural Substances – have not had changes made in their molecular structure as found in nature
Derivatives/ Extractives – chief constituents obtained by extraction
Geographic source & Habitat – region in which the plant or animal yielding the drug grows
Indigenous – growing in their native countries
Naturalized – growing in foreign land
PREPARATION OF DRUGS FOR THE COMMERCIAL MARKET
1. Collection – (small scale) collection time: part of the plant that constitutes the drug is highest in its content of AI
2. Harvesting – (large scale) Collection time
Mechanical devices : pickers, mowers, binders, swath, steel Pectin – citrus fruits
Manual – for potent constituents Unripe fruits - protopectin
Just ripe - pectin
Overripe - pectic acid
3. Drying (Air Drying and Artificial Air Drying)
• remove moisture • fixes the constituents Marijuana
• prevent molding • facilitate grinding and milling Young leaves - cannabidiol
• prevent action of bacteria • prevent environmental hydrolysis Mature leaves - cannabinol (THC)
4. Garbling – final stage; removal of extraneous matter (other parts of the plant, dirt, added adulterants)
5. Packaging, Storage and Preservation
To avoid insect attacks:
a. SIMPLEST METHOD: Expose the drug to 65°C
b. Fumigation with methyl bromide
c. Add adrop of chloroform or carbon tetrachloride
,Examples of Plants in De Materia Medica
Aloe Emollient, tx for burns
Belladonna (beautiful lady) Atropine – mydriatic (SE: cycloplegia) Bioassay
Tamoxifen For breast CA (SE: endometrial CA) Digoxin - pigeon
Colchicum Acute gout Atropine - cats
Allopurinol Chronic gout (Xanthine Oxidase inhibitor) Glucagon - cats
Ergot (“fingers” Claviceps purpurea) Ergotamine (migraine), Ergonovine (oxytocic), Oxytocin - chicken (F)
LSD (hallucinogen) Head drop test - rabbits/rats
Opium (stone of immortality) PTH - dogs
Premarin Estrogen derivative from MARE Heparin - sheep plasma
Digoxin (Digitalis lanata) Insulin - rabbit
Digitoxin (Digitalis purpurea) Lipid soluble, Long half life
Street names of illegal drugs
1. Shabu Ice, Meth
2. Ecstacy Sky
3. Marijuana Hashish, MJ/Maryjane, Pot, Grass, Weed, Cannabis, Indian hemp
EVALUATION OF DRUGS (determine the quality (intrinsic property) and purity (absence of adulterants) of drugs)
1. Organoleptic - by means of the organs of sense; macroscopic appearance
2. Microscopic - essential in the study of adulterant in powdered plants (identity and purity)
3. Biologic - pharmacologic activity of certain drugs has been applied to their evaluation or standardization
4. Chemical - assay of AC using chemicals (titration); best method of determining official potency
5. Physical - physical constants (solubility, spec grav, optical rotation, congealing point, refractive index, MP)
CLASSIFICATION OF DRUGS
Morphology – forms
Taxonomy – phylogeny (natural relationship or among plants and animals)
Pharmacologic or Therapeutic – based on effect on the body
Chemical classification – based on active constituents; Preferred Method of Classification
CHEMISTRY OF NATURAL DRUG PRODUCTS
1. Pharmaceutically active – cause chemical changes in the preparation
2. Pharmacologically active – responsible for the therapeutic activity
3. Inert constituents – no definite pharmacologic activity
4. Secondary plant substance – extracted, crystallized and purified; presence of inert matter which may modify
or prevent absorbability or potency of AC
Drug biosynthesis/Biogenesis – study of the biochemical pathways leading to formation of secondary constituents (drugs)
Primary metabolites to Secondary metabolites
Carbohydrates Glycosides
BIOGENESIS
Proteins OR Tannins
DRUG BIOSYNTHESIS
Fats Volatile oils or
Fixed oils
3 Principal factors that influenced the secondary constituents of drug plants
1. heredity (genetic composition)
2. ontogeny (stage of development)
3. environment (soil, climate, associated flora and method of cultivation)
, CHO 4 cal/g
CARBOHYDRATES AND RELATED COMPOUNDS CHON 4 cal/g
Fats 9 cal/g
polyhydroxyaldehydes or polyhydroxyketones containing C, H and O; same ratio as in H2O (2:1)
1st products of photosynthesis (glucose)
General formula: CnH2nOn | Cn(H2O)n | (CH2O)n
MONOSACCHARIDES
Cannot be hydrolyzed to simple sugar substances that is ketonic or aldehydic substitution product of a polydroxy alcohol
C Name Aldose Ketose
2 Diose Hydroxyacetaldehyde
3 Triose Glyceraldehyde Dihydroxyacetone
4 Tetrose Erythrose Erythrulose
5 Pentose Arabinose, Xylose, Ribose Ribulose
6 Hexose Glucose, Galactose Fructose
7 Heptose Sedoheptose
8 Octulose D-glycero-D-mannoctulose
HEXOSES (most important monosaccharides found in plants)
Other names Uses Identification Test
Glucose D-glucose Nutrient (parenteral), Excipient Moore’s Test
(aldohexose) Dextrose Ca gluconate/gluceptate/levulinate – Ca replenisher (caramel)
Blood sugar Ferrous gluconate – hematinic
Grape sugar
Physiologic sugar
Fructose Fruit sugar Food for diabetics Seliwanoff’s Test
(ketohexose) Levulose (sweetest Ingredient in infant feeding formula
monosaccharide) Ingredient in fructose injection, nutrient
PENTOSES
Xylose (D-xylose, Wood Sugar)
obtained by boiling corn cobs, straw or similar materials with dilute acid to hydrolyze the xylan polymer
diagnostic aid in intestinal malabsorption
OLIGOSACCHARIDES
DISACCHARIDES
Other N Origin Uses
Sucrose Saccharum Saccharum officinarum (cane) Demulcent, Sweetening, Coating, Preservative,
Glu + Fru Cane sugar Beta vulgaris (beets) Production of syrups, Retards oxidation
(non-reducing) Beet sugar Acer saccharum (maple)
Table sugar
Maltose Malt sugar From germination of barley
Glu + Glu
Lactose Milk sugar Cow’s milk (Bos Taurus) Isolation of Lactose
Glu + Gal Butter – cream, united fat globules
Lactulose (Alkaline lactose)
(reducing) Buttermilk – liquid separating from butter
lactic & acetic acid
Skimmed milk – left after cream separates
(irritation, catharsis)
Dec serum NH3 in encephalopathy Cheese – coagulum, skimmed m. + rennin
Whey – liquid separated from coagulum
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