Natural Drugs of Vegetable Origin

Classification of Natural Drugs of Vegetable Origin

• Earth's flora and fauna are highly diverse, including an estimated 2-2.5 lacs of plant species across 300 families and 10,500 genera.
• Between 100 and 150 medicinal plant species are cultivated, with 30-40 grown as large-scale field crops.
• Drugs from animal and mineral sources have been used historically and remain commercially significant.
• Natural drugs are a primary source of curative agents, with exploration extending to marine organisms, which include about 5 lacs species yielding therapeutically active constituents.
• Drug sources include plants, animals, minerals/earth, microorganisms, synthetic/semi-synthetic materials, and recombinant DNA technology.
• Crude drugs are substances used directly or indirectly without chemical modification.
• These drugs are fundamental in pharmacognosy and can be classified in two main categories: organized and unorganized.

Organized Drugs

• Organized drugs have cellular organization with anatomical features, mainly from plant sources.
• Most morphological plant parts or entire plants are considered organized drugs.
• Examples include Cinchona bark, Sandalwood, Quassia wood, Senna, Digitalis leaves, Nux vomica seeds, and Rauwolfia roots.
• Microscopic and anatomical studies are crucial for identifying these drugs.
• Organized drugs can be used directly, modified, or have their active ingredients extracted for medicines like herbal teas, extracts, and tinctures.

Unorganized Drugs

• Unorganized drugs lack morphological or anatomical organization.
• These products, sourced from plants, animals, or minerals, are sold directly.
• Microscopic studies are unnecessary for crude drugs in this category.
• Unorganized drugs include plant exudates like gums, oleogums, oleoresins, oleogum-resins, and plant lattices such as opium.
• This category also includes aloetic juices like aloes and dried extracts like black and pale catechu, along with essential oils, fixed oils, fats, and waxes.
• Some minerals like shilajit also fall into this category.
• These drugs can be solid, semi-solid, or liquid, with quality assessed via physical, chemical, and analytical standards.

Latex

• Latex is found in special plant tissues, typically appearing as a white, aqueous suspension.
• Suspended particles in latex may consist of proteins, sugars, alkaloids, resins, and starch.

Dried Juice

• Dried juice is obtained from fleshy leaves, as with aloes, or from the stems of trees, such as kino.
• This involves making incisions and collecting and drying the juices.

Oleoresins

• Oleoresins are homogenous mixtures of volatile oils and resins, exemplified by oleoresins of ginger, turmeric, and capsicum.

Dried Extract

• Dried extracts of pharmacognostic origin are made by treating plant parts with water or distillation, followed by concentration.
• Drugs of pharmaceutical origin are produced using alcoholic or hydro-alcoholic solutions, adjusted to a standard strength, such as agar, black catechu, and gelatin.

Oleo-gum-resins

• Oleo-gum-resins are homogenous mixtures of volatile oil, gum, and resin; Myrrh is an example.

Gums

• Gums are translucent, amorphous substances produced by plants, generally as a result of unfavorable conditions or injuries.
• Gums are abnormal products of plant metabolism created through a process known as Gummosis.
• They are soluble or partly soluble in water but insoluble in alcohol and most organic solvents.

Differences Between Organized and Unorganized Drugs

• Organized drugs are plant or animal organs made of definite cells and structures.
• Unorganized drugs derive from plant or animal parts through extraction, distillation, incision, or purification.
• Organized drugs are solid, while unorganized drugs can be solid, semi-solid, or liquid.
• Botanical and zoological terms describe organized drugs; physical characteristics like solubility describe unorganized drugs.
• Identifying organized drugs relies on microscopic features.
• Identifying unorganized drugs relies on chemical and physical standards.
• Examples of organized drugs include Digitalis, Cinchona and Fennel.
• Examples of unorganized drugs include Aloe, beeswax, and Opium

Methods of Crude Drug Evaluation

• Evaluating crude drugs employs multiple methods to ascertain identity, quality, and purity.

Organoleptic (Macroscopic) Evaluation

• This involves sensory examination using sight, smell, taste, touch, and sometimes sound.
• It helps in identifying the shape, color, size, texture, and odor of the crude drug.

Microscopic Evaluation

• This involves examining powdered or sectioned plant materials via microscope.
• It identifies cellular structures, trichomes, stomata, starch grains, and other diagnostic features.

Physical Evaluation

• This determines measurable characteristics like moisture content, solubility, viscosity, and swelling index.
• It includes parameters such as ash values (total, acid-insoluble, and water-soluble ash) and extractive values.

Chemical Evaluation

• This uses chemical reagents to detect the presence of active constituents.
• Qualitative and quantitative chemical assays like TLC, HPLC, and spectroscopic methods are included.

Biological Evaluation (Bioassays)

• This tests the pharmacological activity of the crude drug on living organisms or isolated tissues.
• It helps assess potency, efficacy, and safety.

Chromatographic and Spectroscopic Evaluation

• This incorporates advanced techniques like TLC, HPLC, GC-MS, and UV-Vis spectroscopy.
• These techniques are used for compound identification and purity assessment.

Microbiological Evaluation

• This determines microbial contamination, including bacteria, fungi, and pathogens.
• The analysis includes testing for total microbial load, aflatoxins, and endotoxins.

Toxicological Evaluation

• This identifies potential toxic contaminants, such as heavy metals, pesticides, and mycotoxins.
• Toxicological evaluation ensures safety for medicinal use.

Physical Evaluation

• This involves measuring physical constants like moisture content, specific gravity, and optical rotation to evaluate quality.

Crude Drug Classification

• The chief natural drug sources are plants, microbes, animals, and marine organisms, with some from organic and inorganic minerals.
• Studying individual drugs requires a classification system that is simple, easy to use, and unambiguous.
• Drug classification methods include alphabetical, taxonomical, morphological, pharmacological, chemical, chemotaxonomical, and serotaxonomical approaches.

Alphabetical Classification

• Alphabetical classification is the simplest method.
• Crude drugs are arranged alphabetically by Latin, English (common), or local language names.
• Examples of references include the Indian, British, and European Pharmacopoeias, as well as the United States Pharmacopoeia and National Formulary.
• Merits include ease and speed of use, no repetition, and simple tracing and adding entries.
• Demerits include no relationship between previous and successive entries.
• Examples of drugs include Acacia, Benzoin, Cinchona, Dill, Ergot, Fennel, Gentian, and Hyoscyamus.

Taxonomical Classification

• Crude drugs are classified by kingdom, subkingdom, division, class, order, family, genus, and species based on morphological, microscopical, chemical, embryological, serological, and genetic characteristics.
• Angiospermae (Angiosperms) produce flowers, unlike Gymnospermae (Gymnosperms).
• Dicotyledonae (Dicots) have two seed leaves, while Monocotyledonae (Monocots) have one.
• Superorders in Dicotyledonae include Magnoliidae and Rosidae; in Monocotyledonae, they include Alismatidae.
• Orders are divisions of superorders, while families divide orders; family names end in –aceae.
• Subfamilies may divide families and end in -oideae.
• Tribes are divisions within a family and end in –eae.
• Subtribes are divisions of tribes and end in –inae.
• The genus is the familiar plant name, like Papaver (Poppy).
• The species defines an individual plant, named for its features or origins, written in small letters after the genus.
• A variety is slightly different, abbreviated as var.
• A form has minor differences, such as flower color, noted with form (or f.).
• A cultivar is a cultivated variety reproduced by humans, indicated by single quotes or cv.
• Benefits include ease of classification and usefulness in studying evolutionary developments.
• Drawbacks include a lack of correlation with chemical constituents and a failure to recognize organized/unorganized drug natures in morphological studies.

Morphological Classification

• Drugs are categorized by the morphological or external characteristics of plant or animal parts used (e.g., leaves, roots, stem).
• Drugs from plant parts with cellular tissues are considered organized drugs, such as rhizomes, barks, and leaves.
• Drugs prepared via physical processes like incision or extraction without cellular tissues are unorganized drugs; these include aloe juice and opium latex.
• Examples of organized drugs include Quassia and Sandalwood as woods; Digitalis and Mint as leaves; Arjuna and Cinchona as barks; Clove and Saffron as flowering parts.
• Additional examples include Amla and Anise as fruits; Bitter almond and Black Mustard as seeds; Aconite and Ginger as roots and rhizomes; Ergot and Ephedra as plants and herbs; and Cotton and Hemp as hair and fibers.
• Unorganized drugs include Opium and Papain from dried latex; Aloe and Kino from dried juice; Agar and Pectin from dried extracts; Beeswax and Spermaceti waxes; Acacia and Guar Gum as gums.
• Further examples include Benzoin and Colophony resins; Turpentine and Anise volatile oils; Arachis and Castor fixed oils and fats; Bees wax and Honey as animal products; and Bentonite and Talc as fossil organisms and minerals.
• This classification aids in identifying adulteration and is convenient for practical study when the chemical nature is less understood.
• The main disadvantage is the lack of correlation between chemical constituents and therapeutic actions, with potential repetition of drugs or plants.

Pharmacological Classification

• Drugs are grouped by their pharmacological action, main constituent, or therapeutic use, which is a relevant and commonly used method.
• Drugs with cardiotonic action, like digitalis and squill, are grouped together regardless of their plant parts used or their phylogenetic relationships.
• Examples include Fennel (carminative), Aloe (purgative), Digitalis (cardio tonic), Artemisia (anthelmintic), Vinca (anti-cancer), Hyoscymus (anti-spasmodic).
• More examples include Cinchona (anti-malarial), Belladonna (CNS depressant), Tea (CNS stimulant), Ginseng (immunomodulatory), Opium (central analgesic), Datura (anticholinergic), and Liquorice (expectorant).
• The system can suggest drug substitutes when unavailable, and it applies even if drug chemical constituents are unknown.
• The demerit is that drugs with multiple actions may be classified separately, causing ambiguity.
• Drugs are grouped together if they exhibit similar pharmacological uses, despite differences in morphology or chemical nature.

Chemical Classification

• Crude drugs are classified based on their most active constituents, such as alkaloids, glycosides, tannins, carbohydrates, and saponins, irrespective of their morphological or taxonomical characters.
• Examples in the table include:
  • Alkaloids: Cinchona, Datura, Vinca
  • Glycosides: Senna, Aloe, Ginseng
  • Carbohydrates and related: Acacia, Tragacanth, Starch
  • Volatile oil: Clove, Coriander, Fennel
  • Resin and Resin combinations: Benzoin, Tolu Balsam, Balsam of Peru
  • Tannins: Catechu, Tea
  • Enzymes: Papain, Caesin, Trypsin
  • Lipids: Beeswax, Kokum butter, Lanolin
• Chemical classification is a popular approach for phytochemical studies.
• However, ambiguities can occur when particular drugs contain multiple compounds from different groups.

Chemotaxonomical Classification

• This classification system relies on the chemical similarity of taxa, based on relationships between constituents in different plants.
• Chemotaxonomy classifies plants and organisms by chemical constituents like alkaloids, flavonoids, terpenoids, and phenolics.
• Specific chemical constituents characterize certain plant classes, providing insights into taxonomy, relationships, and evolution.
• For instance, tropane alkaloids typically occur in Solanaceae members, serving as a chemotaxonomic marker.
• The classification enhances understanding of the relationship between chemical constituents, their biosynthesis, and action.
• Benefits include:
  • Objective and reliable classification because chemical compounds are stable and not easily influenced by environmental factors.
  • Usefulness for cryptic and closely related species by distinguishing species via chemical profiles.
  • Reflection of evolutionary relationships; chemical constituents exhibit genetic control.
  • Applicability to fragmented or processed samples for pharmacognosy and drug authentication.
  • Aids in drug standardization by ensuring consistency in bioactive compounds.
  • Supports molecular and morphological taxonomy for a comprehensive system.
• Drawbacks include:
  • Complexity and Variability: Chemical composition can vary due to developmental stages conditions.
  • Time-Consuming and Expensive: Requires sophisticated techniques like chromatography and spectroscopy.
  • Limited to Chemical Constituents: It does not consider morphological anatomical, or genetic variations.
  • Difficulty in Interpretation: Similar compounds in unrelated taxa can lead to misclassification.
  • Limited Database for Comparison: Development of chemical data repositories still continue making comparisons challenging.

Importance of Chemotaxonomy in Crude Drug Classification

• Chemotaxonomy helps identify and classify plants based on biochemical markers and assists in new drug discovery by studying plants with similar constituents.
• Useful in authentication, quality control, and supports phylogenetic studies.

Applications of Chemotaxonomy in Crude Drug Study

• Applications include drug discovery to identifying new medicinal plants by studying related species.
• Plays a role in standardization by ensuring quality control based on chemical markers.
• Plant authentication, confirming plant identity through phytochemical profiling is another application
• Understanding evolutionary links between plant families is enabled through Phylogenetic Relationships.

Serotaxonomical Classification

• Serotaxonomy explores the use of serology to solve taxonomical problems, studying antigen-antibody reactions.
• Antigens stimulate antibody formation; antibodies are specific protein molecules produced by plasma cells.
• Proteins carry taxonomic information and serve as antigens in serotaxonomy, which expresses the similarities and differences among taxa.
• Serotaxonomy determines the degree of similarity among taxa by comparing reactions with antigens from various plant sources.
• It also helps in comparing non-morphological characteristics and single proteins from different plant taxa.
• Steps include extracting protein, injecting antigens into animals to form antibodies
• Animals produce specific antibodies producing antiserum made to react in vitro.
• Evaluating homogeneity of antibody extracts reacting to proteins of A with others in B,C,D, and E aids serotaxonomy.

Application of Serotaxonomy in Crude Drug Classification

• Serotaxonomy is useful in authentication and quality control, aiding:
  • Identifying plant with similar chemical properties.
  • Finding impurities and improving purity.
  • Ensuring consistency in medicinal plant products through species identity.
  • Study evolutionary links between species.
• Highly specific and accurate.
• Useful for finding impurities.
• Aided when features lost.

Limitations of Serotaxonomy

• Serotaxonomy requires specialized laboratory techniques in serotaxonomy along with specialized equipment.
• Antigen-antibody reactions vary due to environmental factors.
• It’s limited to Protein-Based Comparisons due to evaluating protein-based features not fully displaying genetic relations with plant age and varying conditions.
• Antibody Production requires a lot of labor to extract and process.

Examples of Drugs Derived from Plants

• Morphine:

  • Source: Papaver somniferum
  • Common Name: Opium poppy
  • Family: Papaveraceae
  • Use: Opioid medication; blocks pain signals and treats moderate to severe pains

• Atropine:

  • Source: Atropa belladonna
  • Common Name: Deadly nightshade
  • Family: Solanaceae
  • Use: Anesthesia, peptic ulcer treatment; reduces heart rate, salivation, and bronchial secretions before surgery

• Hyoscyamine:

  • Source: Hyoscyamus niger
  • Common Name: Henbane/stinking nightshade
  • Family: Solanaceae
  • Composition: contains 3/4 hyoscyamine and 1/4 scopolamine
  • Use: treats stomach, intestine, bladder/bowel control problems, cramping, and Parkinson's disease.

• Scopolamine:

  • Source: Datura stramonium (contains hyoscyamine with some scopolamine and atropine)
  • Common Name: Jimsonweed/devil's trumpet
  • Family: Solanaceae
  • Use: Anticholinergic; prevents nausea and vomiting caused by motion sickness/surgery

• Cocaine:

  • Source: Erythroxylum coca
  • Common Name: Coca
  • Family: Erythroxylaceae
  • Use: Local anesthetic, anti-fatigue agent, antidepressant; powerful central nervous system stimulant with abuse potential

• Quinine:

  • Source: Cinchona officinalis
  • Common Name: Lojabark/Quinaquina
  • Family: Rubiaceae
  • Use: Antimalarial

• Vinblastine/Vincristine:

  • Source: Catharanthus roseus
  • Common Name: Periwinkle/Madagascar periwinkle
  • Family: Apocynaceae
  • Use: treats cancer and acute leukemia that develops in nerve tissue

• Aspirin:

  • Source: Salix alba
  • Common Name: White willow
  • Family: Salicaceae
  • Use: reduces fever, mild to moderate pain and swelling

• Reserpine:

  • Source: Rauvolfia serpentina
  • Common Name: Indian snakeroot/devil pepper
  • Family: Apocynaceae
  • Use: Antihypertensive, tranquilizer