Pharmacognosy: History, Definition and Scope

Contents:

INTRODUCTION
TRADITIONAL INDIAN SYSTEMS OF MEDICINE

INTRODUCTION

NATURE always stands as a golden mark exemplify the outstanding phenomenon of symbiosis.
The biotic and abiotic elements of nature are all interdependent. Plants are indispensable to man.
The three important necessities of life namely food, clothing, shelter and most of other useful products are supplied to him by the plant kingdom.
Nature has provided a complete storehouse of remedies to cure all ailments of mankind. The knowledge of drugs has accumulated over thousands of years as a result of man’s inquisitive nature so that today we possess many effective means of ensuring health care.
The human being appears to be afflicted with more diseases than any other animal species.
There can be little doubt then that he, very early, sought to alleviate his sufferings from injury and disease by taking advantage of plants growing around him.
In the past, almost all the medicines used were from the plants, the plant being man’s only chemist for ages.
Today, a vast store of knowledge concerning the therapeutic properties of different plants has accumulated.
All phyla of plants viz. Thallophyta, Bryophyta, Pteridophyta, and Spermatophyta, (of which conservative estimates place the total number of known species at approximately 3,35,000) contain species that yield official and unofficial products of medicinal importance.
By far, the greatest number of these are derived from plants and include three hundred or more recognized families of Spermatophyta.
The history of herbal medicines is as old as human civilization. The documents, many of which are of great antiquity, revealed that plants were used medicinally in China, India, Egypt, and Greece long before the beginning of the Christian era.
One of the most famous surviving remnants is Papyrus Ebers, a scroll some 60 feet long and a foot wide, dating back to the sixteenth century before Christ.
The text of document is dominated by more than 800 formulae and 700 different drugs. The drugs such as acacia, castor oil and fennel are mentioned along with apparent references to such compounds as iron oxide, sodium chloride, sodium carbonate and sulphur.
Most of the medicinally active substances identified in the nineteenth and twentieth centuries were used in the form of crude extract. In China, many medicinal plants had been in use since 5000 B.C.
The oldest known herbal is Pen-t’sao written by emperor Shen Nung around 3000 B.C. It contains 365 drugs, one for each day of the year. Indians also, worked meticulously to examine and classify the herbs which they came across, into groups called Gunas.
Charaka made fifty groups of ten herbs each of which, according to him, would suffice an ordinary physician’s need. Similarly, Sushrutha arranged 760 herbs in 7 distinct sets based on some of their common properties.
A large portion of the Indian population even today depends on the Indian System of Medicine – Ayurveda, ‘An ancient science of life’. The well-known treatises in Ayurveda are Charaka Samhita and Sushrutha Samhita.
Following the contribution to medicine by Hippocrates” Father of medicine”, (460 – 360 B.C.), Aristotle (384 – 322 BC), Dioscorides (40 – 80 A D.) Galen (131 – 200 A. D.) and the early Arabian physicians, there was a period of approximately 1000 years during which little, if any, progress was made in the medical sciences.
The first pharmacist, Galen, was known to have had a number of pain-relieving materials, including opium in his apothecary. For the next few hundred years, the formulations of the medicaments in use changed very little, although some bold attempts were made by chemical entrepreneurs such as Paracelsus (1493 -1541) to develop mineral salts which might have had the potential of being universal curative agents. However, throughout this period, the use of herbal extracts for medicinal purposes never lost its place.

The importance of the extraction method and alcohol as an extractant was reported by Le’mery (1645-1715). William Withering in 1785 published an account of some of the medicinal properties of foxglove leaves based on ten years of experimentation.
Percolation process was used for the crude drugs. Calumba, an alkaloidal drug, became official in 1788. In 1803, the French pharmacist, Derosne isolated narcotine from opium.
In 1806, Sertuerner isolated morphine from opium and its role in alleviating pain was recognised. In the next few years, strychnine (1817), emetine (1817), brucine (1819), piperine (1819), quinine (1820) and colchicine (1820) were isolated.
The French Pharmacist, Pelletier first reported the isolation of strychnine from ignatius beans and later from nux vomica seeds.
A new extraction process for alkaloid was developed by Stass and Otto in 1852. Other important discoveries during this period were the isolation of nicotine from tobacco leaves (Posselt and Reimann, (1828), cocaine (Neumann, 1860), ouabain (Hardy and Gallows, 1877), pilocarpine (Gerrard and Hardy,1875), ephedrine (Nagai, 1887) and podophyllotoxin (Kuersten, 1891). Isolation of ergometrine, digoxin, reserpine, theophylline and quinidine are the significant discoveries of the twentieth century.
In the nineteenth century, the term ‘Materia Medica’ was used for the subject now known as ‘Pharmacognosy ‘.
While studying Sarsaparilla, it was Seydler, a German scientist, who coined the term ‘Pharmacognosy! in 1815 in the title of his work “Analecta Pharmacognostica”. Pharmacognosy is derived from two Greek words viz. Pharmakon (a drug) and Gignosco (to acquire the knowledge of).
Pharmacognosy may be defined as a branch of bioscience which treats in detail medicinal and related products of crude or primary type obtained from plant, animal and mineral origins.
In short, it is an objective study of crude drugs from natural sources treated scientifically and it encompasses the knowledge of the history, distribution, cultivation, collection, processing for market and preservation, the study of sensory, physical, chemical and structural characters and the uses of crude drugs.
Pharmacognosy also includes study of other materials used in pharmacy such as suspending, disintegrating and flavouring agents, filtering aids, etc. and substances like antibiotics, allergens, hallucinogenic and poisonous plants, immunizing agents, pesticides, raw materials for the production of oral contraceptives, etc.
Swede Linnaeus (1707 – 1778) the great systematist classified the plants and introduced the system of naming the plants known as the binomial system which is still followed.
The progress achieved in botanical studies during 19th century had a direct influence on Pharmacognosy. Plant classification was further developed by Bentham and Hooker (1862-1863), A.W. Eichler (1883), Engler and Prandtl (1887-1898).
In 1865, G. Mendel’s important observations on plant hybrids were published. The introduction of the microscope, as an important analytical tool, was a landmark advancement in botanical research, especially due to the development of several techniques: clearing, mounting and staining of the preparations.
The Anatomical Atlas of Crude Drugs was published by Berg in 1865. Later in the century, Voehl, Tschirch and others reported the anatomical characters of several powdered drugs which proved to be of great significance especially at a period when adulteration in both drugs and food articles was common. ‘An Anatomical Atlas of Powdered Vegetable Drugs’ was compiled in 1904 by Greenish and Collin.
Pharmacognosy as an applied science has played a crucial role in the development of different disciplines of science.
A pharmacognosist should possess a sound knowledge of the terms used to describe the vegetable and animal drugs as covered under botany and zoology, respectively.
The knowledge of plant taxonomy, plant breeding, plant pathology, and plant genetics is helpful in the development of cultivation technology for medicinal and aromatic plants.
Plant – chemistry (phytochemistry) has undergone significant development in recent years as a distinct discipline. It is concerned with the enormous variety of substances that are synthesised and accumulated by plants and the structural elucidation of these substances.
The technology involving extraction, purification and characterisation of pharmaceuticals from natural sources is a significant contribution to the advancement of natural and physical sciences.
The knowledge of chemotaxonomy, biogenetic pathways for formation of medicinally active primary and secondary metabolites, plant tissue culture and other related fields is essential for complete understanding of Pharmacognosy.
The basic knowledge of biochemistry and chemical engineering is essential for development of collection, processing and storage technology of crude drugs.
Pharmacognosy is an important link between Pharmacology and Medicinal Chemistry. As a result of rapid development of phytochemistry and pharmacological testing methods in recent years, new plant drugs are finding their way into medicine as purified phytochemicals, rather than in the form of traditional galenical preparations.
The knowledge of pharmacology is essential for understanding action of drugs on animals and the human system.
Pharmacognosy is the infrastructure on which depends evolution of novel medicines, as it is seen that several crude drugs are utilized for preparation of galenicals or as sources of therapeutically significant substances that cannot be synthesised economically.
Further, the crude drugs also provide essential intermediates for final synthesis of active compounds.
Phytopharmaceuticals or synthetic drugs derived from phytochemicals have to be ultimately incorporated in suitable dosage form which involves the knowledge of dispensing and preparative pharmacy, pharmaceutical technology and analysis.
In a nutshell, Pharmacognosy is an important bridge between the pharmaceutical and basic sciences. Pharmacognosy is a vital link between Ayurvedic and Allopathic systems of medicines.
It provides a system wherein the active principles of crude drugs derived from natural origin can could be dispensed, formulated and manufactured in dosage forms acceptable to allopathic system of medicine.

TRADITIONAL INDIAN SYSTEMS OF MEDICINE

1. Ayurveda:

The system of Ayurveda-Ancient Science of Life originated in India about 3000 years ago.
It is one of the oldest systems of medicine identified exclusively with ancient Indian civilization and dealing with both preventive and curative aspects of life.
The principles of positive health and therapeutic measures embedded in this system relate to mental, physical, social and spiritual welfare of human beings.
Ayurveda encompasses the knowledge of Kayachikitsa (Internal medicine), Kaumarbhritya (Paediatrics), Trahchikitsa (Psychological medicine), Shalakya Tantra (Otorhinolaryngology and Ophthalmology), Shalya Tantra (Surgery) Agada Tantra (Toxicology), Rasayana Tantra (Geriatrics) and Vajikarana Tantra (Eugenics and Aphrodisiacs).
The Pharmacopocia of Ayurveda consists of more than 8000 recipies made of natural drugs derived from herbal, mineral, animal and marine sources.
These are used singly or in combinations and in varied forms such as decoctions, infusions, distillates, extracted juices, powders, pills, tablets, syrups, fermented liquids, bhasmas, medicated oils etc.

2. Unani System of Medicine

The roots of this system go deep to the times of the well known Greek philosopher Hippocrates who is credited with it. Aristotle Golen (384 – 322 BC) Greek – Philosopher “Father of natural history” made valuable contributions to it. This system of Greek origin was further carried to Persia (Iran), where it has been improved by Arabian physicians.
This system is based on two theories viz. the Hippocratic theory of four humours and the Pythagorian theory of four proximate qualities. The four humours are blood, phelgm, yellow bile and black bile while the four qualities are the states of living human body like hot, cold, moist and dry.
They are represented as earth, water, fire and air. The Greek ideas were put by Arabian physicians as seven working principles (Umur-e-Tabia) and included elements, temperaments, humours, organs, life, spirit, energy and actions. They believed that these principles are responsible for the body constitution and its health, as well as, the diseased conditions.
The Unani system of medicine aims at treating the cause of disease and not its symptoms. For this purpose, thorough history of the patient is recorded in addition to his pulse, urine and stool examinations.
The diseased condition is considered to be due to the imbalance between humours and accordingly, treatment is given. The drugs are polyherbal formulations and their collective effect is considered.
Unani system of medicine is called by various names in different parts of world such as Arab medicine, Greco-Arab medicine, Loniah medicine, Islamic medicine and also Oriental medicine.
Unani-medicines: Madar, fufal, Gilo, Kabab chini, Karanj, Kulthi, Lodh, Qust, Sana, Tagar, Zeera, Siyah.

3. Homeopathic System of Medicine

In comparison to other traditional systems of medicine, Homeopathy is a newer one and has been developed in the eighteenth century by Samuel Hahnemann – a German physician and chemist.
He proposed that the cause of disease itself can be used for its treatment. Hahnemann put forth the Law of Similars which says that like cures like (Similae similibus curentur). With this principle, he showed that cinchona can produce the symptoms of malaria.
He succeeded in getting relevant results with a large number of extracts prepared from plants, animals and minerals. He compiled all these observations in what is called ‘The Organon of Medicine.’
In the homoeopathic system, the drug treatment is not specified, but the choice of drug depends on symptoms and the clinical condition of the patient.
This is based on the concept of proving and prover. In a healthy person called prover, the symptoms created by different doses of drug extracts are noted which is called proving, and it specifically considers physical, mental and emotional changes of the prover.
Consequently, these symptoms are compared with a patient with similar symptoms and accordingly, same type of extract is given for treatment. During the treatment, the drug extracts are extremely diluted, which is believed to cause potentiation and enhancement of curative effect.
The drugs are extracted in the form of mother tincture, which is further diluted in terms of decimal or centesimal potencies. Various medicinal plants used in homoeopathy are:

4. Siddha System of Medicine

The term ‘ Siddha ‘ means achievement and ‘ Siddhars ‘ were saintly personalities, who attained proficiency in medicine through practice of Bhakti and Yoga.
This is the system of pre-vedic period identified with Dravidian culture and it is largely therapeutic in nature. Like Ayurveda, this system believes that all objects in universe are made up of five basic elements namely, earth, water, sky, fire and air.
The identification of causative factors of diseases is done through pulse reading, colour of body, study of voice, urine examination, status of digestive system and examination of tongue. The literature of Siddha system is mostly in Tamil.
Few natural drugs used in Siddha system of medicine are:

Abini : (Papaver — somniferum),
Alari : (Nerium — Indicum),
Ethi : (Strychnous — Nux vomica),
Gomathi : (Datura — stramonium),
Haikalli : (Ephorbia — nerifolia),
Rotha Polam : (Aloe — barbadensis)

5. Naturopathy and Yoga

Naturopathy is not merely a system of treatment, but also a way of life, which is based on laws of nature. The attention is particularly paid to eating and living habits, adoption of purificatory measures, use of hydrotherapy, mud packs, baths, massage etc.
The system of Yoga is as old as Ayurveda. The eight components of Yoga are restraint, observance of austerity, physical postures, restraining of sense organs, breathing exercises, contemplation, meditation and samadhi.
Yoga exercises have potential in improvement of better circulation of oxygenated blood in the body, restraining the sense organs, improvement of social and personal behaviour and induction of tranquility and serenity in the mind.