Pharmacognosy

Organic chemistry; Biochemistry; Biology

Theoretical matrix (T):

-Expository methodology using the appropriate audiovisual means.

– Adoption of interactive strategies mediated through resources from the Internet, when plausible.

Practical matrix (P):

Execution of laboratory work related to the extraction, identification and qualitative and quantitative chemical characterization of the main active molecules present in drugs of natural origin  as well as raw materials.

This curricular unit aims to bring together a body of knowledge that allows students to identify the main groups of drugs of natural origin and their medicinal plants, as well as the correct application of methodologies employed in medicinal plants processing towards extractive solution obtention and quantitative and qualitative characterization.

At the same time, it addresses the core concepts for the correct characterization of the raw materials of natural origin most used in Pharmacy, as well as their analytical methodologies.

Theoretical matrix (T):

 1. Pharmacognosy as a multidisciplinary science:

Historical review: From prehistory to the 18th century; 19th century and isolation of the first alkaloids of natural origin: the boom of organic and industrial chemistry; 21st century and discovery of new bioactive molecules – transgenic plants.

2. Primary and secondary metabolism:

Primary metabolites and corresponding metabolic pathways;

Secondary metabolites as a source of pharmacologically active substances: shikimic acid pathway and acetate pathway.

3. Chemical structure, biological and pharmacological effects of drugs and/or raw materials characteristic of the following groups of drugs:

• Glucids

 Fundamentals and chemical characterization: aldose and ketosis.

Classification of osides – holosides and heterosides.

Distinction between reducing and non-reducing sugars. Tests related to their research and determination: phenylhydrazine derivatization reaction, reduction of Fehling’s reagent, Molish test, Selivanoff, Keller-Kiliani.

Honey – chemical constitution. Determination of reducing sugar content using the modified Lane and Eynon technique; determination of apparent sucrose content by the Walker method.

Poly-holosides: Starch, Cellulose – Applications in Pharmacy.

Polyuronides: Gums and mucilages – applications in Pharmacy.

Gum analysis by thin layer chromatography (TLC) and high pressure liquid chromatography (HPLC) – study of current tests in the Portuguese Pharmacopoeia.

• Lipids

 Saturated and unsaturated fatty acids.

Chemical composition of fatty drugs.

Classification: homolipids and heterolipids.

Monographic study of the following fatty drugs: castor oil, almond oil, coconut oil, cod liver oil, cocoa butter, spermaceti, lanolin and beeswax.

Oxidative and hydrolytic alterations of fatty drugs – characteristic indices.

Saponification reaction and determination of the unsaponifiable.

• Aromatic drugs

 Volatile oils: definition and physicochemical properties.

Heterogeneous chemical constitution: terpenes and isoprene rule. Polymerization of isoprene and classification of terpenes as a function of the number of isoprene units. Terpenoids.

Classification and monographic study of aromatic drugs: turpentine essence, lavender, rosemary, peppermint, eucalyptus and Ceylon cinnamon.

Processes for obtaining volatile oils: Flowering, water vapor entrainment, extraction with organic solvents, pressing (or expression), extraction by supercritical CO2.

Analytical study of essential oils: organoleptic tests (smell and taste of essential oils), determination of 1,8-cineole by crystallization, gas chromatography.

• Alkaloids

 General definition and properties.

Alkaloid biosynthesis and predominance in different families of the plant kingdom.

Pyrrolidinic and tropic alkaloids (atropine, hyoscyamine, scopolamine, cocaine) – chemical characterization and pharmacological effects.

Pyridinic and piperidine alkaloids (pomegranate, hemlock) – chemical characterization and pharmacological effects.

Indole alkaloids (vomica nut, rye ergot) – chemical characterization and pharmacological effects.

Quinoleic alkaloids (quine) – chemical characterization and pharmacological effect.

Isoquinoleic alkaloids (curares, opium) – chemical characterization and pharmacological effect.

General alkaloid reagents.

Monographic study of Quina Casca and Opium according to the Portuguese Pharmacopoeia.

• Drugs with anthracenic glycosides

 Quinones: Benzoquinones, naphthoquinones and anthraquinones.

Chemical characterization of the anthracene nucleus.

 Free anthraquinones and anthracene glycosides (C-heterosides and O-heterosides): corresponding pharmacological activities.

Reduced and oxidized forms of genins: toxic and therapeutic properties.

“Hypericum perforatum L.” and “Hypericum androsemum L.”- anxiolytic and hepatoprotective activity.

Monographic study of the following drugs with anthracene glycosides: Rhubarb, cascara sagrada, black alder, senna and aloe.

Identification and assay of anthracene drugs: Borntraeger reaction, genins assay using HPLC.

• Cardiotonic glycosides

 Characterization of structural and pharmacological homogeneity.

The cyclopentane-perhydrophenanthrene nucleus.

Chemical composition of a cardiotonic heteroside: lactone ring, steroid nucleus and osidic fraction. Preponderant stereochemical considerations for pharmacological activity.

Distinction between bufadienolides and cardenolides.

Cardiotonic glycosides and their occurrence in species of the genus “Digitalis”: “Digitalis purpurea L.” and “Digitalis lanata Ehrh”.

Pharmacological effects of digitalis: negative chronotropic effect, positive ionotropic effect and regularization of cardiac rhythm.

Mechanism of action: inhibition of the Na+/K+ ATPase pump. Pharmacological interactions.

Digitalis intoxication.

Monographic study of Dedaleira leaves according to the Portuguese Pharmacopoeia.

Extraction, identification and determination of cardiotonic heterosides: “salting-out” technique and characteristic reactions to identify the lactone ring, steroid nucleus and osidic fraction.

• Phenolic compounds

 The problem of antioxidants: concept of free radical, oxidative stress, reactive oxygen and nitrogen species and preferential targets. Endogenous antioxidant defenses (enzymatic and non-enzymatic systems). Preventive, intercept and repair antioxidants. Legally permitted pro-oxidant and antioxidant mechanisms.

 Natural antioxidants: L-ascorbic acid, ascorbyl palmitate, tocopherols and phenolic compounds.

Phytoantioxidants: simple phenols, phenolic acids, flavonoids, coumarins, lignans and tannins – chemical characterization and occurrence. Mechanism of action: Inhibition of Fenton and Haber-Weiss reaction.

Soy isoflavones (Glycine max) and antioxidant and phytoestrogenic properties: chemical characterization of daidzein and genistein as well as pharmacological action.

Berrie’s polyphenols (Vaccinium L.) and antioxidant properties: chemical characterization of phenolic acids and flavonoids as well as the corresponding pharmacological action

Quantification of antioxidants: Analytical methods, methods for the determination of antioxidant power (ABTS, TRAP) and analytical determination of Vitamin C – Tillmans method.

Practical matrix (P):

Students are provided with a set of practical work protocols centered on extraction methodologies and subsequent analysis of naturally occurring compounds with pharmacological activity

NAO

Primary bibliography:

– COSTA, A. F., FARMACOGNOSIA, Vol. I, 5.ª edição, Fundação Calouste Gulbenkian, 2002

– COSTA, A. F., FARMACOGNOSIA, Vol. II 5.ª edição, Fundação Calouste Gulbenkian, 2002

– COSTA, A. F., FARMACOGNOSIA, Vol. III, 5.ª edição, Fundação Calouste Gulbenkian, 2002

Secondary bibliography:

– Portuguese Pharmacopeia 

– Lectures