Pharmacognosy is the study of crude drugs obtained from medicinal plants, animals, fungi, and other natural sources. [1] 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". [2]
The word "pharmacognosy" is derived from two Greek words: φάρμακον, pharmakon (drug), and γνῶσις gnosis (knowledge) or the Latin verb cognosco (con, 'with', and gnōscō, 'know'; itself a cognate of the Greek verb γι(γ)νώσκω, gi(g)nósko, meaning 'I know, perceive'), [3] meaning 'to conceptualize' or 'to recognize'. [4]
The term "pharmacognosy" was used for the first time by the German physician Johann Adam Schmidt (1759–1809) in his published book Lehrbuch der Materia Medica in 1811, and by Anotheus Seydler in 1815, in his Analecta Pharmacognostica.
Originally—during the 19th century and the beginning of the 20th century—"pharmacognosy" was used to define the branch of medicine or commodity sciences ( Warenkunde in German) which deals with drugs in their crude, or unprepared form. Crude drugs are the dried, unprepared material of plant, animal or mineral origin, used for medicine. The study of these materials under the name Pharmakognosie was first developed in German-speaking areas of Europe, while other language areas often used the older term materia medica taken from the works of Galen and Dioscorides. In German, the term Drogenkunde ("science of crude drugs") is also used synonymously.
As late as the beginning of the 20th century, the subject had developed mainly on the botanical side, being particularly concerned with the description and identification of drugs both in their whole state and in powder form. Such branches of pharmacognosy are still of fundamental importance, particularly for botanical products (widely available as dietary supplements in the U.S. and Canada), quality control purposes, pharmacopoeial protocols and related health regulatory frameworks. At the same time, development in other areas of research has enormously expanded the subject. The advent of the 21st century brought a renaissance of pharmacognosy, and its conventional botanical approach has been broadened up to molecular and metabolomic levels. [5]
In addition to the previously mentioned definition, the American Society of Pharmacognosy defines pharmacognosy as "the study of natural product molecules (typically secondary metabolites) that are useful for their medicinal, ecological, gustatory, or other functional properties." [6] Similarly, the mission of the Pharmacognosy Institute at the University of Illinois at Chicago involves plant-based and plant-related health products for the benefit of human health. [7] Other definitions are more encompassing, drawing on a broad spectrum of biological subjects, including botany, ethnobotany, marine biology, microbiology, herbal medicine, chemistry, biotechnology, phytochemistry, pharmacology, pharmaceutics, clinical pharmacy, and pharmacy practice.
All plants produce chemical compounds as part of their normal metabolic activities. These phytochemicals are divided into (1) primary metabolites such as sugars and fats, which are found in all plants; and (2) secondary metabolites—compounds which are found in a smaller range of plants, serving more specific functions. [8] For example, some secondary metabolites are toxins used by plants to deter predation and others are pheromones used to attract insects for pollination. It is these secondary metabolites and pigments that can have therapeutic actions in humans and which can be refined to produce drugs—examples are inulin from the roots of dahlias, quinine from the cinchona, THC and CBD from the flowers of cannabis, morphine and codeine from the poppy, and digoxin from the foxglove. [8]
Plants synthesize a variety of phytochemicals, but most are derivatives: [9]
A typical protocol to isolate a pure chemical agent from natural origin is bioassay-guided fractionation, meaning step-by-step separation of extracted components based on differences in their physicochemical properties, and assessing the biological activity, followed by next round of separation and assaying. Typically, such work is initiated after a given crude drug formulation (typically prepared by solvent extraction of the natural material) is deemed "active" in a particular in vitro assay. If the end-goal of the work at hand is to identify which one(s) of the scores or hundreds of compounds are responsible for the observed in vitro activity, the path to that end is fairly straightforward:
In vitro activity does not necessarily translate to biological activity in humans or other living systems.
In the past, in some countries in Asia and Africa, up to 80% of the population may rely on traditional medicine (including herbal medicine) for primary health care. [10] Native American cultures have also relied on traditional medicine such as ceremonial smoking of tobacco, potlatch ceremonies, and herbalism, to name a few, prior to European colonization. [11] Knowledge of traditional medicinal practices is disappearing in indigenous communities, particularly in the Amazon. [12] [13] [14]
With worldwide research into pharmacology as well as medicine, traditional medicines or ancient herbal medicines are often translated into modern remedies, such as the anti-malarial group of drugs called artemisinin isolated from Artemisia annua herb, a herb that was known in Chinese medicine to treat fever. However, it was found that its plant extracts had antimalarial activity, leading to the Nobel Prize winning discovery of artemisinin. [15] [16]
Microscopic evaluation is essential for the initial identification of herbs, identifying small fragments of crude or powdered herbs, identifying adulterants (such as insects, animal feces, mold, fungi, etc.), and recognizing the plant by its characteristic tissue features. Techniques such as microscopic linear measurements, determination of leaf constants, and quantitative microscopy are also utilized in this evaluation. The determination of leaf constants includes stomatal number, stomatal index, vein islet number, vein termination number, and palisade ratio. [17]
The stomatal index is the percentage formed by the number of stomata divided by the total number of epidermal cells, with each stoma being counted as one cell.
where:
S.I. is the stomatal index
S is the number of stomata per unit area
E is the number of epidermal cells in the same unit area. [18]
Alkaloids are a class of basic, naturally occurring organic compounds that contain at least one nitrogen atom. This group also includes some related compounds with neutral and even weakly acidic properties. Some synthetic compounds of similar structure may also be termed alkaloids. In addition to carbon, hydrogen and nitrogen, alkaloids may also contain oxygen or sulfur. Rarer still, they may contain elements such as phosphorus, chlorine, and bromine.
The terpenoids, also known as isoprenoids, are a class of naturally occurring organic chemicals derived from the 5-carbon compound isoprene and its derivatives called terpenes, diterpenes, etc. While sometimes used interchangeably with "terpenes", terpenoids contain additional functional groups, usually containing oxygen. When combined with the hydrocarbon terpenes, terpenoids comprise about 80,000 compounds. They are the largest class of plant secondary metabolites, representing about 60% of known natural products. Many terpenoids have substantial pharmacological bioactivity and are therefore of interest to medicinal chemists.
Secondary metabolites, also called specialised metabolites or secondary products, are a type of natural product generated by lifeforms that are not directly involved in the normal growth, development, or reproduction of the organism. Instead, they generally mediate ecological interactions, which may produce a selective advantage for the organism by increasing its survivability or fecundity. Specific secondary metabolites are often restricted to a narrow set of species within a phylogenetic group. Secondary metabolites often play an important role in plant defense against herbivory and other interspecies defenses. Humans use secondary metabolites as medicines, flavourings, pigments, and recreational drugs.
Herbal medicine is the study of pharmacognosy and the use of medicinal plants, which are a basis of traditional medicine. With worldwide research into pharmacology, some herbal medicines have been translated into modern remedies, such as the anti-malarial group of drugs called artemisinin isolated from Artemisia annua, a herb that was known in Chinese medicine to treat fever. There is limited scientific evidence for the safety and efficacy of many plants used in 21st-century herbalism, which generally does not provide standards for purity or dosage. The scope of herbal medicine sometimes includes fungal and bee products, as well as minerals, shells and certain animal parts.
Phytochemicals are chemical compounds produced by plants, generally to help them resist fungi, bacteria and plant virus infections, and also consumption by insects and other animals. The name comes from Greek φυτόν (phyton) 'plant'. Some phytochemicals have been used as poisons and others as traditional medicine.
Saponins are bitter-tasting, usually toxic plant-derived secondary metabolites. They are organic chemicals and have a foamy quality when agitated in water and a high molecular weight. They are present in a wide range of plant species throughout the bark, leaves, stems, roots and flowers but particularly in soapwort, a flowering plant, the soapbark tree, common corn-cockle, baby's breath and soybeans. They are used in soaps, medicines, fire extinguishers, dietary supplements, steroid synthesis, and in carbonated beverages. Saponins are both water and fat soluble, which gives them their useful soap properties. Some examples of these chemicals are glycyrrhizin and quillaia, a bark extract used in beverages.
Artemisia annua, also known as sweet wormwood, sweet annie, sweet sagewort, annual mugwort or annual wormwood, is a common type of wormwood native to temperate Asia, but naturalized in many countries including scattered parts of North America.
Artemisinin and its semisynthetic derivatives are a group of drugs used in the treatment of malaria due to Plasmodium falciparum. It was discovered in 1972 by Tu Youyou, who shared the 2015 Nobel Prize in Physiology or Medicine for her discovery. Artemisinin-based combination therapies (ACTs) are now standard treatment worldwide for P. falciparum malaria as well as malaria due to other species of Plasmodium. Artemisinin is extracted from the plant Artemisia annua an herb employed in Chinese traditional medicine. A precursor compound can be produced using a genetically engineered yeast, which is much more efficient than using the plant.
Medicinal plants, also called medicinal herbs, have been discovered and used in traditional medicine practices since prehistoric times. Plants synthesize hundreds of chemical compounds for various functions, including defense and protection against insects, fungi, diseases, and herbivorous mammals.
A natural product is a natural compound or substance produced by a living organism—that is, found in nature. In the broadest sense, natural products include any substance produced by life. Natural products can also be prepared by chemical synthesis and have played a central role in the development of the field of organic chemistry by providing challenging synthetic targets. The term natural product has also been extended for commercial purposes to refer to cosmetics, dietary supplements, and foods produced from natural sources without added artificial ingredients.
Phytochemistry is the study of phytochemicals, which are chemicals derived from plants. Phytochemists strive to describe the structures of the large number of secondary metabolites found in plants, the functions of these compounds in human and plant biology, and the biosynthesis of these compounds. Plants synthesize phytochemicals for many reasons, including to protect themselves against insect attacks and plant diseases. The compounds found in plants are of many kinds, but most can be grouped into four major biosynthetic classes: alkaloids, phenylpropanoids, polyketides, and terpenoids.
Ocimum tenuiflorum, commonly known as holy basil, tulsi or tulasi, is an aromatic perennial plant in the family Lamiaceae. It is widely cultivated throughout the Southeast Asian tropics. It is native to tropical and subtropical regions of Asia, Australia and the western Pacific. This plant has escaped from cultivation and has naturalized in many tropical regions of the Americas. It is an agricultural and environmental weed.
Ethnomedicine is a study or comparison of the traditional medicine based on bioactive compounds in plants and animals and practiced by various ethnic groups, especially those with little access to western medicines, e.g., indigenous peoples. The word ethnomedicine is sometimes used as a synonym for traditional medicine.
Uncaria tomentosa is a woody vine found in the tropical jungles of South and Central America. It is known as cat's claw or uña de gato in Spanish because of its claw-shaped thorns. The plant root bark is used in herbalism for a variety of ailments, and is sold as a dietary supplement.
Dennettia tripetala is a species of flowering plant in the Annonaceae family. It is a shrub or tree native to western and west-central tropical Africa, including Guinea, Sierra Leone, Ghana, Nigeria, and Cameroon. It is threatened by habitat loss.
Justicia gendarussa, commonly known as Willow-leaved justicia ,Lapsulis in Creole Seychelles; is a small erect, branched shrub. According to Plants of the World Online it is native to the Indian subcontinent, Indochina, Peninsular Malaysia, Sumatra, the Philippines, and New Guinea, and has been introduced to Nepal, the western Himalayas, Pakistan, southern China including Hainan and Taiwan, eastern Africa, and the Mascarene Islands, Comoro Islands, and Seychelles. It has been described as rare and endemic to India, though those claims are at least confusing, in the context of statements that the plant is widely used in various forms for many of its medicinal and insecticidal properties, and that it is a quick-growing, evergreen forest shrub considered to be a native of China and distributed in Sri Lanka, India and Malaysia.
Alpinia nigra is a medium-sized herb belonging to the ginger family. The rhizome is well known in many Asian cultures as a medicinal and culinary item. In many Asian tribal communities it is a part of the diet along with rice.
Psychoactive plants are plants, or preparations thereof, that upon ingestion induce psychotropic effects. As stated in a reference work:
Psychoactive plants are plants that people ingest in the form of simple or complex preparations in order to affect the mind or alter the state of consciousness.
Luz Oliveros-Belardo was a Filipina pharmaceutical chemist, honored with the National Scientist of the Philippines award by the Philippine government in 1987.
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