SOURCES OF DRUGS – PLANTS, ANIMALS, MARINE AND TISSUE CULTURE
1.2.1 Natural Products
A natural product a chemical compound or substance produced by a living organism - found in nature is that usually has a pharmacological or biological activity for use in pharmaceutical drug discovery and drug design. A natural product can be considered as such even if it can be prepared by total synthesis. Natural products may be extracted from tissues of terrestrial plants, marine organisms or microorganism fermentation broths. A crude (untreated) extract from any one of these sources typically contains novel, structurally diverse chemical compounds, which the natural environment is a rich source of. The basicdifference between active constituents and phytoconstituents is also important to identify the therapeutic active principles in the plants. Phytoconstituents are the whole chemical constituents that are present in the plants and active constituents are the specific chemical constituents that are therapeutically active or are responsible for medicinal activity that are isolated from other extracted chemical constituents. The most important things are to identify the natural origin plant sources like shrub, tree, creeper and herbs that are the most basic criteria for authentication of the plant. Further traditional plants, complementary/alternative medicine, endangered plants, medicinal plants, aromatic plants and natural products are also important terminologies that are quite similar, but exact knowledge of these will provide good skill to the Pharmacognosists for research and to develop new drug molecules.
Shrub: A shrub is distinguished from a tree by its multiple stems and shorter height, usually under 6 m (20 ft) tall.
Tree: A tree is a perennial woody plant. It typically has many secondary branches supported clear of the ground by a single, self-supporting main stem or trunk.
Creeper: It is a prostate or trailing plant that spreads by means of stems that creep. These plants creep along the soil surface, though unlike climbers, they have strong stems and firm grip on the soil
. Herb: As per the botanists, an herb is a plant with no woody stem above ground distinguished from tree or a shrub. In general terms, any part of the vegetable species that can be used for medicine, cosmetic, culinary or such purposes is known as herb. The roots, leaves, bark, fruits, flowers, stem or any part of the plant can be used for these purposes.
Traditional plant medicine: It is a system of plant based on cultural beliefs from generation to generation and practices handed down to formulate the medicines for curing the diseases. Traditional medicine is the total of the knowledge, skills, and practices based on the theories, beliefs, and experiences indigenous to different cultures, whether explicable or not, used in the maintenance of health as well as in the prevention, diagnosis, improvement or treatment of physical and mental illness.
Complementary/alternative medicine (CAM): The terms “complementary medicine” or “alternative medicine” are used interchangeably with traditional medicine in some countries. They refer to a broad set of health care practices that are not part of that country’s own tradition and are not integrated into the dominant health care system.
Endangered plant species: An endangered plant species is a population of plants which is facing a high risk of becoming extinct because it is either few in numbers, or threatened by changing environmental or predation parameters such as habitat destruction, climate change, or pressure from invasive species.
Medicinal plants: Medicinal herbs are plants or parts of plants used for therapeutic or medical benefit. Aromatic plants: Plants that produce and exude aromatic substances (largely ether oils), which are used in making perfumes, in cooking and in the food, pharmaceutical and liquor industries.
Plant source is the old source of the drugs. Whole parts of the plants are used like leaves, stem, bark, fruits, roots etc. Some important natural drugs that are procured from, plant sources are listed in table 1.2
1.2.3 Drugs obtained from Marine Sources
There are more than 5 lakhs species of marine organisms available in seas and ocean. They are used for many important therapeutic activities. The enormous ecological resources of the sea and ocean have been exploited since ancient times and the use of marine animals like fish and preparations from algae are included as the sources of medicine. Oceans contain
more than 80% of diverse plant and animal species. Such organisms like sponges, tunicates, fishes, soft corals, nudibranchs, sea hares, opisthobranch Molluscs, echinoderms, bryozoans, prawns, shells, sea slugs and marine microorganisms are sources of bioactive compounds. The drugs that are procured from the marine sources are depicted in tables 1.4 and 1.5.
1.2.4 Plant Tissue Culture
It is an in-vitro cultivation of plant cells, tissues and organs in liquid or semi-solid nutrient media under aseptic and controlled environment. In this method primary and secondary plant metabolites are regenerates. The basic criteria for plant tissue culture are totipotency and plasticity. Totipotency is defined as regeneration capacity of the selected plant parts whereas plasticity is the withstand capacity of plants in any stressful condition. The plant tissue culture technique is important because isolation of bioactive compounds from the medium is very easy, rare and endangered plant species are micropropagated and cultivated in mass scale, production of immobilized plant cell for future use and even biochemical conversion is easy etc.
Applications:
• Mass scale production of plants.
• Conservation of endangered plant species.
• Cultivation of disease resistance plants.
• Production of micropropagated plants. Advantages:
• Some plants, which do not multiply by seeds, can be propagated through plant tissue culture technique.
• More amounts of secondary metabolites are produced.
• Large number of plants can be produced in a short time.
• Chemicals which are used in the tissue culture increase the capacity of produced plants to resist with biocidal chemicals, environment stress and competitive to survive over weed.
• Isolation of constituents from plant is easy.
• Mass propagation of plants is easy
ORGANIZED DRUGS AND UNORGANIZED DRUGS
All crude drugs are mainly two types based on their sources. If the drugs are procured from cellular parts of plants in raw form is known as organized crude drugs whereas the drugs that are procured from non-cellular parts of plants are known as unorganized crude drugs. The details of these two categories of drugs are discussed in below morphological classification.
1.4 CLASSIFICATION OF DRUGS
Alphabetical, morphological, taxonomical, chemical, pharmacological, chemo and sero taxonomical classification of drugs. In India there are more than 17500 flowering plants, out of which 2000 plants are used in various classical systems of medicine like Ayurveda, Siddha and Unani. Traditionally, about 8000 species of wild plants are used as medicine. The drugs used in Indian System of Medicine are 90% based on plant material and are considered to be safe, cost effective and with minimal or no side effects when genuine ingredients are used. To follow the study of the individual drugs, one must adopt some particular sequence of arrangement, and this is referred to a system of classification of drugs. A method of classification should be simple, easy to use; and free from confusion and ambiguities. Due to diversity, drugs are classified as:
1. Alphabetical classification.
2. Morphological classification.
3. Taxonomic classification.
4. Pharmacological classification.
5. Chemical classification.
6. Chemo-taxonomical classification.
7. Sero-taxonomical classification
1.4.1 Alphabetical Classification
This classification provides arrangement of crude drugs in alphabetical order of their Latin and English names or sometimes local names. This method is adopted in many books like Indian Pharmacopoeia, British Pharmacopoeia, United States Pharmacopoeia and National Formulary, British Herbal Pharmacopoeia, British Pharmaceutical Codex, European
Pharmacopoeia (Latin Titles), Encyclopedia of common Natural ingredients used in Drugs and cosmetics. In Indian Pharmacopoeia 1966 names changed to English, like Amylum changed to starch, Acacia gum changed to Indian gum etc. Example: Acacia, Benzoin, Cinchona, Dill, Ergot, Fennel, Gentian, Hyoscyamus, Ipecacuanha, Jalap, Kurchi, Liquorice, Myrrh, Nux-Vomica, Opium, Podophyllum, Quassia, Rauwolfia, Senna, Uncaria Gambier, Vasaka, Wool Fat, Yellow Bees Wax, Zedoary.
Advantages:
• This method provides quick reference search of the crude drugs.
• Study of drugs by this method is easy once the name of the drug is known.
• In this system location, tracing and addition of drug entries is easy.
Disadvantage:
• There is no relationship between the previous and successive drug entries 1.4.2 Morphological Classification All crude drugs are arranged according to the external characters of the plant or animal parts i.e., leaves, roots, stems, flowers from plants etc. This class of drug is further classified as organized and unorganized drug. The organized drugs are obtained from the cellular tissues and dried parts of the plants like, Rhizomes, barks, leaves, fruits, entire plants, hairs, fibres etc. The plant drugs are prepared by some intermediate physical processes like incision, drying or extraction with a solvent and some are do not contain any cellular plant tissues which are called unorganized drugs, e.g., aloe juice, opium latex, agar, gelatin, tragacanth, benzoin, honey, beeswax, lemon grass oil etc. The differences are given in table 1.6.
Advantages:
• Easy method to study of plant drugs.
• Even if the chemical content or action of drug is not known the drug can be studied properly.
• It gives idea about the source of drugs.
• It gives idea whether it is organized or unorganized.
• Easy to identify and detect the adulteration.
Disadvantages: • During collection, drying and packing, morphology of drug changes; they are difficult to study.
• No correlation between chemical constituents with therapeutic actions.
• Repetition of drugs or plants occurs.
1.4.3 Taxonomical Classification
This is the systematic naming of organisms into similar groups. Plant taxonomy uses the gross morphology like flower form, leaf shape, fruit form, etc. of plants to separate them into similar groups. Quite often the characteristics that distinguish the plants become a part of their name. For example, a white oak (Quercus alba) is named because of the white leaf. Taxonomical classification is purely a botanical classification; it is based on principles of natural relationship and evolutionary developments. They are grouped in
Kingdom, Phyllum, Order, Family, Genus and Species. The entire plant is not used as drug; only a part of plant is used as a drug. E.g. cinnamon bark. It is classified scientifically as follows:
Kingdom: Plantae
Division: Magnoliophyta
Order: Proteales
Family : Proteaceae
Subfamily: Grevilleoideae
Genus: Telopea
Species: Speciosissima
Taxonomists classify two species together in the same genus (the plural is genera). For example, the horse Equus caballus and the donkey Equus assinus are both placed in the genus Equus. Similar genera are brought together to form a family. Similar families are classified within an order. Orders with similar characteristics are grouped in a class. Related classes are grouped together as divisions or phyla (the singular is phylum). For plants and fungi divisions are used while phyla are used for animals and animal-like organisms. The largest and broadest category is the kingdom.
Examples:
Phylum: Spermatophyta
Division: Angiospermae
Class: Dicotyledons
Order: Rosales
Family: Leguminosae
Sub-family: Papilionaceae
Genus: Glycyrrhiza, Astragalus, Myroxylon
Species: Glycyrrhiza glabra, Astragalus gummifer, Myroxylon balsamu
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