PHARMACOGNOSY UNIT - 1 (PART-A)
Pharmakon-drug; Greek
Gignosco/gnosis= to acquire a knowledge
The American Society of Pharmacognosy defines pharmacognosy as “the study of the physical, chemical, biochemical and biological properties of drugs, drug substances or potential drugs or drug substances of natural origin as well as the search for new drugs from natural sources”. It is also defined as the study of crude drug.
The term Pharmacognosy was first introduced by Johan Adam Schimdtin his hand written manuscript Lehrbuch der Materia Medica. In 1815 C. A. Seydler, a German medical student again introduced the term in his research work Analecta Pharmacognostica’
Applied science and technology deals with
- Botanical/zoological
- Chemical
- Biochemical
- Biological
- Pharmacological
- Economical
- Ecological
aspects of dug from natural origin.
- Pharmacognosy deals with botanical (or zoological/geological), morphological, microscopical, chemical, biochemical, pharmacological, biological, economical, ecological aspects of drugs from natural origin.
- It deals with the cultivation, collection, drying, processing, isolation, purification of plants with medicinal and pharmaceutical importance
- Pharmacognosy deals with standardization and evaluation of crude drugs.
- It is very important in drug discovery process.
- Pharmacognosy deals with standardization and evaluation of herbal medicine.
- Knowledge of Pharmacognosy is essential for the development of new pharmaceutical aids.
- It is essential for standardization of indigenous system of medicine and ethnomedicine.
- Knowledge of Pharmacognosy is essential for the development of new cosmeceuticals and nutraceuticals.
- Modern pharmacognosy is essential for the knowledge of biogenetic pathway of secondary metabolites.
- Pharmacognosy is also dealing with discovery and collections of novel and classical drugs from Marine sources.
- Newer approaches of Pharmacognosy utilize different biotechnological approaches in drug development from natural sources.
- Pharmacognosy deals with in vitro culturing of pharmaceutically important plants.
- Knowledge of Pharmacognosy is essential for sustainable and ecological uses of medicinal plant.
Sources of drug
Allopathic drugs include:
- Substances and specified devices meant for treatment, mitigation, prevention of diseases or disorders in human beings or animals.
- Insect repellents and substances meant for destruction of vermis and insects causing disease in human being and animals.
- Substance meant to affect any structure or function of human body.
- Contraceptive
Like all other discoveries, the inspiration drug development is nature. Along with allopathic medicine,all Traditional system of medicine (TSM) directly rely upon nature as a source of drug. The major 2 sources of drugs are natural and chemical synthesis. Allopathic system based on isolated compound from natural source whereas TSM uses powder crude drugs or their derivatives.
The high number of drugs are introduced from natural source. Natural source includes plants, animal, microbes and marine organisms.
Plants
Plants used as drug, from prehistorical time. Still plant is the major source of drugs in conventional and alternative system of medicine.
Maximum numbers of drugs are from Spermatophytes. Among spermatophyte the Angiosperms are higher than gymnosperm as a source of drugs.
Gymnosperms can be considered as a source of volatile oil, resin(colophony/ pine oil) and alkaloid like ephedrine.
Both monocots and dicots of angiosperm can be considered as a source of drugs.
Along with higher plants, some lower plants can be used as a source of drugs. Ergot is a fungal drug which is a source of number of important alkaloids
Many fungi and bacteria are the source of different antibiotics. Some fern shows potential taenicidal properties.
Animal
Certain animal part or product can be used as a source of drug.
Thyroid is the modified preparation of thyroid glands of sheep and pigs and use a source of thyroxine and liothyronine.
Conjugated oestrogen was collected from pregnant mares.
Insulin was initially collected from pancreas of all vertebrate. Now it is prepared through rDNAtechnology.
Oxytocin is obtained from the pituitary glands of cattles and pigs.
Trypsin and chymotrypsin, proteolytic enzymes are obtained from pancreas of ox.
Liver and stomach from cattles are converted into suitable preparation used in pernicious anemia as replacement therapy.
Apart from drugs pharmaceutical aids are also obtained from animal sources. Colouring principle ofcochineal insects, cantharides, heparin, cod liver oils, wool fat, bees wax, honey obtained from animal sources.
Marine sources
Number of Pharmaceutical substance and drugs are obtained from marine sources.
Agar- dried colloidal concentrate from decoction of red algae (Gelidium amansii/Garcilia).
Alginic acid- obtained from brown algae (Laminaria sp.)
Carrageenan – obtained from Chondrus crispus (Rhodophyceae).
Sparmaceti-obtained from the head of sperm whale (Physeter macrocephalus)
Ichthammol and diatomaceous earth – obtained from fossilized marine fish. And unicellular algae.
Protamine –a heparin antagonist obtained from sperm of salmon fish.
Pralidoxime – choline esterase reactivator obtained from the electric eel.
Kainic acid- an anthelmintic obtained from the marine red algae Digenea simplex.
Cod liver oil- source of vitamin A and D obtained from fresh liver of cod fish.
Apart from this classical drug number of novel cytotoxic, antivral, antimicrobials are obtained from different marine sources.
Crude Drugs
Drugs which are collected from nature and no other process has been carried out except collection and drying.
Morphologically crude drugs are classified according to 2 categories:
Organised drug – Drugs which represent any cellular portion or organ of plant or animal. E.g.
Unorganized drugs: drugs derived from plants or animals part but do not represent any cellular part or organ of plant or animal.eg.
Classification is the categorization of drugs in different categories
Crude drugs can be classified using following system of classification:
- Alphabetical classification
- Morphological classification
- Chemical classification
- Taxonomical classification
- Chemotaxonomical classification
- serotaxonomical classification
1. Alphabetical classification: Crude Drugs are classified according to their common name inalphabetical order. This method is implemented in different Pharmacopoeia. Eg. British Pharmacopoeia.
Eg, acacia, benzoin, cinchona, digitalis, ephedra, fennel, gentian
Merits: Easy to find out the drug without knowing their morphology, active constituents, indication.
Demerits: no chemical or pharmacological relationship between previous and next drugs.
2. Morphological classification: Crude Drugs are classified according to their external or morphological appearance. According to this system drugs are broadly classified into 2 categories viz. Organized and Unorganized drugs.
Organized drugs: Crude drugs contain cellular part or organ structure.
Unorganized drugs: Crude drugs do not contain cellular part or organ structure.
Merits: it is essential for collection and preliminary evaluation of drugs from natural origin. Also essential for botanical standardization.
Demerits: this system of classification does not follow any chemical or pharmacological relationship. Repetition of same drug occur where more than one part of drug is used.
Organized drug: Drugs which represent any cellular portion or organ of plant or animal.Eg.
Unorganised drugs: drugs derived from plants or animals part but do not represent any cellular part or organ of plant or animal.eg.
3. Chemical classification: Drugs are classified according to their active constituents (chemicals that are responsible for the therapeutic effects of the drug). E.g.
- Carbohydrate or derivative products- Acacia, honey, isapgul
- Glycoside- senna, aloe, rhubarb
- Tannin-catechu, gall, myrobalan
- Volatile oils- clove, fennel, coriander
- Resin-colophony, asafetida
- Alkaloids- vinca, ergot
Merits-This system of classification is essential for new drug discovery process and phytochemical standardization, because the active constitute is responsible for therapeutic activities.
Demerits- It is difficult to classify those drugs with more than one different chemical classes of chemical constituents.eg. Nutmeg contains both fixed oil and volatile oils.
This classification does not consider Pharmacological and morphological aspect of drugs.
4. Taxonomical classification: Drugs are classified according their systematic position in nature. E.g.
Phylum: Spermatophyta
Division: angiospermae
Class: Dicotyledons
Order: Rosales
Family: Leguminosae
Genus: Glycyrrhiza
Species: glabra
Merits-It is very essential for botanical description of medicinal plants and indirectly useful for morphological identification. eg. Umbelliferae fruits are cremocarps. This classification is also essential to reduce the confusion of different vernacular names.
Demerits- this classification does not correlate the chemical constituents and pharmacological aspect of drug.
5. Pharmacological/Therapeutic classification:
Crude drugs are categorized according to their Pharmacological or therapeutic action. E.g.
- Drugs acting on gastrointestinal system
Bitters- gentian, chirata
Carminative- fennel, cardamom
Laxative-aloe, senna - Drugs act on respiratory system-
Expectorant- vasak, tulsi
Bronchodilator- ephedra - Drugs acting on cardiovascular system-
Cardiotonics- digitalis, squill Antihypertensive- rouwolfia - Drugs acting on central nervous system- Central analgesic- opium CNS stimulant-coffee
5.Anticancer- vinca, podophyllum
- Laxatives- Aloes, Rhubarb, Castor oil, Ispaghula, Senna.
- Cardiotonics- Digitalis, Arjuna.
- Carminatives & G.I. regulators- Coriander, Fennel, Ajowan, Cardamom, Ginger, Black pepper , Asafoetida, Nutmeg, Cinnamon, Clove.
- Astringents- Catecheu.
- Drugs acting on nervous system- Hyoscyamus, Belladonna, Aconite, Ashwagandha, Ephedra, Opium, Cannabis, Nux -vomica.
- Antihypertensive- Rauwolfia.
- Antitussives- Vasaka, Tolu balsam, Tulsi.
- Antirheumatics- Guggal, Colchicum.
- Antitumour- Vinca.
- Antileprotics- Chaulmoogra oil.
- Antidiabetics- Pterocarpus, Gymnema sylvestro.
- Diuretics- Gokhru, Punarnava.
- Antidysenterics- Ipecacuanha.
- Antiseptics and disinfectants- Benzoin, Myrrh, Neem, Curcuma.
- Antimalarials- Cinchona.
- Oxytocics- Ergot.
- Vitamins- Shark liver oil and Amla.
- Enzymes- Papaya, Diastase, Yeast
Merits- Very easy to find out a drug for specific therapeutic requirement.
Demerits- Difficult to place a drug with more than one different therapeutic uses. Eg. Cinchona shows antimalarial effect due to presence of quinine and also shows antiarrythmic activity due to presence of quinidine.
6. Chemotaxonomical classification-
Drugs are classified according to their chemical constituents and their taxonomic position in nature. This system considers phylogenetic relationship with secondary metabolite genesis.
Eg. Solanaceae family plants contain tropane alkaloids; Umbelliferae family plants contain volatile oil.
Merits-Chemotaxonomical relationship is essential for new drug discovery process.
Demerits- Highly sophisticated technique; requires DNA hybridization, amino acid sequencing.
7. Serotaxonomical classification- Serotaxonomy can be considered as application of serology on taxonomical classification. Serology is the study of antigen-antibody reaction. This reaction may be same or different in different taxa. On this basis drugs may be classified without considering their morphological aspects in taxonomy.
- Serotaxonomy can be considered as application of serology on taxonomical classification. Serology is the study of antigen-antibody reaction. This reaction may be same or different in different taxa. On this basis drugs may be classified without considering their morphological aspects in taxonomy.
- The classification of very similar plants by means of differences in the proteins they contain.
- Protein extracted from a plant is injected into the blood of an animal
- where it behaves as an antigen
- After an interval for the production of antibodies, a blood sample is taken.
- This can be used to compare the first plant protein (antigen) with extracts taken from other plants.
Merits: helps in comparing nonmorphological characteristics, which helps in the taxonomical data.
- This technique also helps in the comparison of single proteins from different plant taxa.
Demerits: sophisticated instruments are required.
- Not beneficial for phylogenic establishment