Drugs from Plant Sources PDF

DRUGS FROM PLANT SOURCES  WHAT IS PHARMACOGNOSY? Pharmacognosy is the study of drugs of natural origin. The American Society of Pharmacognosy defines pharmacognosy as "the study of the physical, chemical, biochemical and biological properties of drugs, drug substances or pot...

DRUGS FROM PLANT SOURCES  WHAT IS PHARMACOGNOSY? Pharmacognosy is the study of drugs of natural origin. 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". The contemporary study of pharmacognosy can be divided into the fields of Medical ethnobotany : the study of the traditional use of plants for medicinal purposes Ethnopharmacology : the study of the pharmacological qualities of traditional medicinal substances Phytotherapy : the medicinal use of plant extracts Phytochemistry : the study of chemicals derived from plants (including the identification of new drug candidates derived from plant sources)  MEDICINAL PLANTS 1900 – over half of drugs in U.S. Pharmacopeia from plants 2001 – about 25% of drugs in U.S. Pharmacopeia from plants, but many synthetic compounds are based on plant-produced structures, or start with plant materials Many plant derived drugs that are currently used in western medicine as prescription medicines were discovered by studying folk knowledge of the plant’s properties  MEDICINAL PLANTS Only about 15% of the known plant species have been screened for medicinal purposes Most medicinal plants come from the tropics Most medicinal plants have been identified by the indigenous people by trial and error 50% of the 250,000 plant species are from the tropics  MEDICINAL PLANTS The most significant medicinal plants used for prescription drugs contain Terpenoids, Steroids and Alkaloids The rapid destruction of our tropical rainforests threatens the development of potentially useful drugs There are a host of non-prescription plant remedies which have medicinal uses. these are often referred to as “herbal medicines”  COMPOUNDS FROM PLANTS Primary Metabolites these are mainly the products of photosynthesis, which provides the food that enables the plant to live, grow and reproduce. these are the substances necessary for the primary functions of life and keep the plant healthy and alive and include proteins, fats, sugars, organic acids etc.  COMPOUNDS FROM PLANTS Secondary Metabolites these are usually unique to a plant or group of plant very diverse and thought to be a secondary function for the plant such as protection now it is known that they have evolved to improve the chances of the species’ survival most of our medicinal herbs are used because of their secondary metabolites  it is the secondary metabolites which provide the pharmacological activity  SECONDARY METABOLITES-CONTINUE Sometimes present in extremely minute concentrations These include alkaloids, phenolics, sterols, steroids, essential oils, lignins, tannins etc They are responsible for the strong flavours and bitter taste of some species They act as defense chemicals e.g. bitter tastes to repel grazing animals alkaloids and other compounds to poison predators bright colours to attract birds and insects for pollination antimicrobial substances to resist bacterial / fungal or viral attack compounds which prevent other plants from growing nearby  MEDICINES FROM PLANTS modern western medicine (since late 19th century) is focused on single, isolated compounds or now (since the 1950s) preferably synthetic substances because they can easily be produced in large amounts however, compounds are still isolated from plants if they cannot be easily synthesized semisynthesis, starting with a plant-derived compound, which is then modified either biologically or chemically, is also a much used means of producing desired drugs DRUGS ISOLATED FROM PLANTS  ARTEMISININ antimalarial properties of extracts of annual or sweet wormwood (artemisia annua l.) a traditional chinese drug for fevers and malaria selectively toxic to various species of plasmodium (falciparum, vivax, ovale) in vitro and in vivo  CARDIAC GLYCOSIDES Two of the Digitalis genus, D. purpurea L. (purple foxglove) and D. lanata Ehrh. (Grecian foxglove), are used for the extraction of digitoxin and digoxin The cardenolide glycosides are still important drugs in the treatment of heart insufficiency  OPIUM raw opium is the air-dried latex obtained by incision from the unripe capsules of opium poppy , papaver somniferum l. it contains not less than 10.0% morphine and not less than 2.0% codeine. the alkaloids found in opium poppy, have long been used to alleviate pain. Morphine is one of the principal alkaloids of opium. These alkaloids are very addictive, but are potent pain killers (analgesics) Codeine, another morphine alkaloid, is a potent antitussive agent, that is, it inhibits coughing Morphine is acetylated to produce heroin  EPHEDRA infusions of ephedra spp. have been used for thousands of years in china. there it is often called "ma huang". in the 1920's the plant was "discovered" by western medicine and the active compounds isolated. ephedrine and a series of related compounds are used today as decongestants (e.g., in sudafed, robitussin etc.) and to treat low blood pressure most of the active compounds are made synthetically, however.  VINBLASTINE AND VINCRISTINE vinblastine and vincristine are binary indole alkaloids isolated from the aerial parts of the madagascan periwinkle They are cytotoxic effective drugs vs. lymphomas (hodgkin’s disease)  ASPIRIN Historically, it was known that extracts of willow bark (salix spp., salicaceae) and leaves alleviated pain the compound that is responsible is called "salicin“ but it is too irritating to take internally in the late 1800's, acetylsalicylic acid (Aspirin) was discovered. It can be taken orally and is an effective analgesic, anti-inflamatory, and antipyretic  COCAINE the indians of andean south america have long used coca leaves (from erythroxylum coca, erythroxylaceae) as a stimulant the indians chewed the leaves mixed with lime to free the alkaloids. the alkaloids reduced feelings of hunger and pain later when the alkaloids were isolated, it was discovered that they had local anesthetic properties cocaine has been used for surgery (especially dental surgery)  TAXOL the antitumor activity of taxol (paclitaxel), a diterpene alkaloid from the bark of several taxus species (pacific yew) taxol is useful for treating several types of tumors, but was originally developed for ovarian tumors. it is also quite feasible to prepare taxol by semisynthesis  PROBLEMS RELATED TO PLANT SOURCES Identification of plants Climate and social conditions of the area Season of collection Condition of storage Standardization of active principle Purity of active ingredients Maintenance of supply line  HERBAL MEDICINES herbal medicines are preparations made from whole plants or whole parts of plants e.g. barks, roots, flowers, leaves, rhizome, etc invariably contain a mixture of ingredients, some of which may be pharmacologically active frequently marketed as dietary supplements, which are not required to have proven efficacy, safety, or quality in the united states and most other countries mostly used by consumers for self-treatment of minor symptoms the majority of which have not been scientifically tested EXAMPLES OF HERBAL MEDICINES  GINKGO (GINKGO BILOBA) complex of phytomedicinals from the leaves improves blood flow improves memory in older people effective free-radical scavenger  ECHINACEA (ECHINACEA SPECIES) Extracts from shoot, root and rhizome acts as immune-stimulant speeds up cycle of cold virus and flu  GINSENG (PANAX GINSENG) mixture of compounds from root traditional Chinese medicine for 5000 years increases stress tolerance speeds up metabolism anti-carcinogenic  CHAMOMILE mixture of terpenoids, coumarins, and flavonoids from dried flower heads soothes stomach-aches anti-inflammatory, anti- spasmodic and anti-bacterial actions mild sedative  FEVERFEW sesquiterpenoid lactones from leaves used for 2000 years effective head-ache treatment, especially migraines  EVENING PRIMROSE OIL evening primrose, oenothera biennis l., originally a north american species, is cultivated in the united kingdom and canada for the production of seeds. the seeds contain up to 25% oil rich in polyunsaturated fatty acids. in germany and the united kingdom, evening primrose oil is approved for treatment of atopic eczema  GARLIC (ALLIUM SATIVUM) ONION (ALLIUM CEPA) organo-sulfur compounds from bulbs anti-carcinogenic and anti- microbial anti-atherosclerosis and anti- hypertensive toxic in high amounts  MILK THISTLE complex of flavolignans from seeds protects liver against toxins helps against hepatitis and cirrhosis of the liver  ST. JOHN’S WORT extract from leaves effective for depression and sleeplessness anti-retroviral activities (AIDS)  SAW PALMETTO from fruits increases frequency of urination treatment for prostate cancer protects against edema (water retention) and inflammation  GINGER from the rhizome over 12 compounds with anti- oxidant activities greater than vitamin E anti-tumor anti-emetic (inhibits vomiting)  SOYBEANS contains phytoestrogens like isoflavones reduces health risks associated with menopause: osteoporosis and heart disease in women reduces prostrate, colon and breast cancer ISOLATION OF DRUGS FROM PLANT SOURCES  STANDARDIZED EXTRACTS FOR CRUDE DRUGS if a plant contains several groups of biologically active compounds, it is not always possible to know which compound is responsible for the activity and then it is wiser to produce an extract plant extracts may also be standardized to contain a certain amount of one component or group of components known to possess biological activity the extract thus obtained may be ready for use as a medicinal agent in the form of tinctures and fluid extracts, it may be further processed to be incorporated in any dosage form such as tablets or capsules, or it may be fractionated to isolate individual chemical entities plant extracts are used in phytotherapy, whereas extracted, purified compounds are used in official medicine.  EXTRACTION involves the separation of medicinally active portions of plant or animal tissues from the inactive or inert components by using selective solvents in standard extraction procedures the extract thus obtained may be ready for use as a medicinal agent in the form of tinctures and fluid extracts, it may be further processed to be incorporated in any dosage form such as tablets or capsules, or it may be fractionated to isolate individual chemical entities  GENERAL PRINCIPLES OF EXTRACTION an extraction solvent must readily dissolve the substance to be extracted, yet it must be only sparingly soluble in the solvent it should extract only the desired substance or as small an amount as possible of any other substance present it should not react chemically with the solute in an undesirable way it should be easily separated from the desired solute after extraction, this requirement can be met if the solvent has low-boiling point and easily removed by distillation  GENERAL METHODS OF EXTRACTION OF MEDICINAL PLANTS  MACERATION in this process, the whole or coarsely powdered crude drug is placed in a stoppered container with the solvent and allowed to stand at room temperature for a period of at least 3 days with frequent agitation until the soluble matter has dissolved the mixture then is strained, the marc (the damp solid material) is pressed, and the combined liquids are clarified by filtration or decantation after standing  INFUSION fresh infusions are prepared by macerating the crude drug for a short period of time with cold or boiling water these are dilute solutions of the readily soluble constituents of crude drugs  DIGESTION this is a form of maceration in which gentle heat is used during the process of extraction. it is used when moderately elevated temperature is not objectionable  DECOCTION in this process, the crude drug is boiled in a specified volume of water for a defined time it is then cooled and strained or filtered this procedure is suitable for extracting water-soluble, heat- stable constituents.  PERCOLATION this is the procedure used most frequently to extract active ingredients in the preparation of tinctures and fluid extracts a percolator (a narrow, cone-shaped vessel open at both ends) is generally used HOT CONTINUOUS EXTRACTION (SOXHLET) in this method, the finely ground crude drug is placed in a porous bag made of strong filter paper, which is placed in chamber of the soxhlet apparatus the advantage of this method, compared to previously described methods, is that large amounts of drug can be extracted with a much smaller quantity of solvent