View source for Pharmacognosy

{{Short description|Study of drugs obtained from natural sources}}
{{distinguish|Pharmacology}}
[[File:Arabic herbal medicine guidebook.jpeg|thumb|350px|[[Dioscorides]]’ ''[[Materia Medica]]'', {{circa|1334}} copy in Arabic, describes medicinal features of various [[plants]].]]

'''Pharmacognosy''' is the study of [[crude drug]]s obtained from [[medicinal plant]]s, [[animal]]s, [[fungi]], and other natural sources.<ref>{{Cite web |last1=Fields |first1=Deborah |last2=Zoppi |first2=Lois |date=2016-08-01 |title=What is Pharmacognosy? |url=https://www.news-medical.net/health/What-is-Pharmacognosy.aspx |access-date=2023-03-09 |website=News-Medical.net |language=en}}</ref> The [[American Society of Pharmacognosy]] defines pharmacognosy as "the study of the physical, chemical, [[Biochemistry|biochemical]], and biological properties of drugs, drug substances, or potential drugs or drug substances of natural origin as well as the [[Drug discovery|search for new drugs]] from natural sources".<ref>[https://web.archive.org/web/19981201075709/http://www.phcog.org/definition.html The American Society of Pharmacognosy]</ref>

== Description ==
The word "pharmacognosy" is derived from two [[Greek language|Greek]] words: {{lang|grc|φάρμακον}}, {{Transliteration|grc|pharmakon}} ([[drug]]), and {{lang|grc|γνῶσις}} ''[[gnosis]]'' ([[knowledge]]) or the [[Latin]] verb ''[[Cognition#Etymology|cognosco]]'' ({{Lang|la|con}}, 'with', and {{lang|la|gnōscō}}, 'know'; itself a [[cognate]] of the [[Ancient Greek|Greek]] verb {{lang|grc|γι(γ)νώσκω}}, {{Transliteration|grc|gi(g)nósko}}, meaning 'I know, perceive'),<ref>{{cite journal |last=Harrison |first=E. |date=November 1929 |title=Liddell and Scott, Part IV – A Greek-English Lexicon. Compiled by H. G. Liddell and R. Scott. A new edition … by H. Stuart Jones and R. Mckenzie. Part IV.: ⋯ξευτον⋯ω—θησαυριστικ⋯ς. Oxford: Clarendon Press, 1929. Paper, 10s. 6d. |journal=The Classical Review |volume=43 |issue=5 |page=189 |doi=10.1017/s0009840x00053762 |issn=0009-840X}}</ref> meaning 'to conceptualize' or 'to recognize'.<ref>{{cite book |date=2011-01-01 |editor1-last=Franchi |editor1-first=Stefano |editor2-last=Bianchini |editor2-first=Francesco |title=The Search for a Theory of Cognition |doi=10.1163/9789401207157 |isbn=9789401207157}}</ref> 

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 (''{{linktext|Warenkunde}}'' in German) which deals with [[drug]]s 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 ''{{linktext|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 ''{{linktext|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 [[Metabolomics|metabolomic]] levels.<ref>{{cite journal |last=Dhami |first=N. |year=2013 |title=Trends in Pharmacognosy: A modern science of natural medicines |journal=[[Journal of Herbal Medicine]] |volume=3 |issue=4 |pages=123–131 |doi=10.1016/j.hermed.2013.06.001}}</ref>

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."<ref>{{cite web |url=http://www.pharmacognosy.us/what-is-pharmacognosy/ |title=About the ASP |publisher=[[American Society of Pharmacognosy]]}}</ref> 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.<ref>{{cite web |url = https://pharmacognosy.pharmacy.uic.edu/ |title=Pharmacognosy Institute}}</ref> 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]].

* medical [[ethnobotany]]: the study of traditional uses of plants for medicinal purposes;
*[[ethnopharmacology]]: the study of pharmacological qualities of traditional medicinal substances;
* [[phytotherapy]]: the study of medicinal use of plant extracts;
*[[phytochemistry]]: the study of chemicals derived from plants (including the identification of new drug candidates derived from plant sources);
*[[zoopharmacognosy]]: the process by which animals self-medicate, by selecting and using plants, soils, and insects to treat and prevent disease;
*[[marine pharmacognosy]]: the study of chemicals derived from marine organisms.

== Biological background ==
[[File:Primula aka.jpg|right|thumb|The [[carotenoids]] in [[Primulaceae|primrose]] produce bright red, yellow and orange shades.]]
All plants produce [[chemical compounds]] as part of their normal [[metabolism|metabolic]] activities. These [[phytochemicals]] are divided into (1) [[primary metabolites]] such as [[sugar]]s and [[fat]]s, which are found in all plants; and (2) [[secondary metabolites]]—compounds which are found in a smaller range of plants, serving more specific functions.<ref name="meskin-2002-p123">{{cite book |last=Meskin |first=Mark S. |title=Phytochemicals in Nutrition and Health |publisher=[[CRC Press]] |year=2002 |isbn=9781587160837 |page=123 |url=https://books.google.com/books?id=cJHsMALUDj0C&pg=PA123 |via=[[Google Books]]}}</ref> For example, some secondary metabolites are [[toxin]]s used by plants to [[Plant defense against herbivory|deter predation]] and others are [[pheromone]]s 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 [[dahlia]]s, [[quinine]] from the [[cinchona]], [[THC]] and [[Cannabidiol|CBD]] from the flowers of [[cannabis]], [[morphine]] and [[codeine]] from the [[poppy]], and [[digoxin]] from the [[digitalis|foxglove]].<ref name="meskin-2002-p123" />

Plants synthesize a variety of [[phytochemical]]s, but most are derivatives:<ref>{{cite book |last1=Springbob |first1=Karen |last2=Kutchan |first2=Toni M. |chapter=Introduction to the different classes of natural products |editor-last=Lanzotti |editor-first=Virginia |title=Plant-Derived Natural Products: Synthesis, Function, and Application |publisher=Springer |year=2009 |isbn=9780387854977 |page=3 |chapter-url=https://books.google.com/books?id=Y8SpVXEng4QC&pg=PA3 |via=[[Google Books]]}}</ref>
* [[Alkaloids]] are a class of chemical compounds containing a nitrogen ring. Alkaloids are produced by a large variety of organisms, including bacteria, fungi, plants, and animals, and are part of the group of natural products (also called secondary metabolites). Many alkaloids can be purified from crude extracts by acid-base extraction. Many alkaloids are toxic to other organisms.
* [[Polyphenol]]s ({{aka}} phenolics) are compounds that contain [[phenol]] rings. The [[anthocyanin]]s that give grapes their purple color, the [[isoflavone]]s, the [[phytoestrogen]]s from [[soy]] and the [[tannin]]s that give tea its astringency are phenolics.
* [[Glycosides]] are molecules in which a sugar is bound to a non-carbohydrate moiety, usually a small organic molecule. Glycosides play numerous important roles in living organisms. Many plants store chemicals in the form of inactive glycosides. These can be activated by enzyme hydrolysis, which causes the sugar part to be broken off, making the chemical available for use.
* [[Terpenes]] are a large and diverse class of [[organic compounds]], produced by a variety of plants, particularly [[conifers]], which are often strong smelling and thus may have a protective function. They are the major components of [[resin|resins]], and of [[turpentine]] produced from resins. When terpenes are modified chemically, such as by oxidation or rearrangement of the carbon skeleton, the resulting compounds are generally referred to as ''[[terpenoids]]''. Terpenes and terpenoids are the primary constituents of the essential oils of many types of plants and flowers. Essential oils are used widely as natural flavor additives for food, as fragrances in perfumery, and in traditional and alternative medicines such as aromatherapy. Synthetic variations and derivatives of natural terpenes and terpenoids also greatly expand the variety of aromas used in perfumery and flavors used in food additives. The fragrance of [[rose]] and [[lavender]] is due to [[monoterpene]]s. The [[carotenoid]]s produce shades of red, yellow and orange in [[pumpkin]], [[maize]], and [[tomato]]es.

=== Natural products chemistry ===
[[File:Digoxin.svg|thumb|right|[[Digoxin]] is a purified [[cardiac glycoside]] that is extracted from the [[foxglove]] plant, ''[[Digitalis lanata]]''. Digoxin is widely used in the treatment of various heart conditions.]]

A typical protocol to isolate a pure chemical agent from natural origin is [[Fractionation|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:
# fractionate the crude extract, e.g. by solvent partitioning or chromatography.
# test the fractions thereby generated with ''in vitro'' assays.
# repeat steps 1) and 2) until pure, active compounds are obtained.
# determine structure(s) of active compound(s), typically by using spectroscopic methods.
''In vitro'' activity does not necessarily translate to biological activity in humans or other living systems.

=== Herbal ===
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.<ref>{{cite web |title=Traditional Medicine |website=[[World Health Organization]] |url=https://www.who.int/mediacentre/factsheets/fs134/en/index.html |archive-url=https://web.archive.org/web/20040428035649/http://www.who.int/mediacentre/factsheets/fs134/en/index.html |url-status=dead |archive-date=April 28, 2004 |access-date=2009-03-12}}</ref> 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.<ref>{{cite web |url=http://www.aidsinfonet.org/fact_sheets/view/708 |title=Native American/Alaska Native Traditional Healing {{!}} aidsinfonet.org {{!}} The AIDS InfoNet |website=www.aidsinfonet.org |access-date=2016-02-24}}</ref> Knowledge of traditional medicinal practices is disappearing in indigenous communities, particularly in the Amazon.<ref>{{cite book |last=Farnsworth |first=N. R. |chapter=The role of ethnopharmacology in drug development |title=Bioactive Compounds from Plants |series=Ciba Foundation Symposium 154 |publisher=Wiley Interscience |location=New York |year=1990}}</ref><ref>{{cite book |last=Farnsworth |first=N. R. |chapter=Screening plants for new medicines |veditors=Wilson EO, Peters FM |title=Biodiversity |location=Washington DC |publisher=National Academy Press |year=1988 |pages=83–97}}</ref><ref>{{cite book |last=Balick |first=M. J. |chapter=Ethnobotany and the identification of therapeutic agents from the rainforest |title=Bioactive Compounds |series=Ciba Foundation Symposium 154 |publisher=Wiley Interscience |location=New York |year=1990 |pages=22–31}}</ref>

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.<ref>{{cite magazine |title=This Ancient Chinese Remedy Helped Win the Nobel Prize |url=https://time.com/4061207/nobel-prize-medicine-ancient-chinese-remedy/ |access-date=2021-10-11 |magazine=[[Time (magazine)|Time]] |language=en}}</ref><ref>{{cite journal |last1=Su |first1=Xin-zhuan |last2=Miller |first2=Louis H. |date=November 2015 |title=The discovery of artemisinin and Nobel Prize in Physiology or Medicine |journal=Science China Life Sciences |volume=58 |issue=11 |pages=1175–1179 |doi=10.1007/s11427-015-4948-7 |issn=1674-7305 |pmc=4966551 |pmid=26481135}}</ref>

== Microscopical evaluation ==
Microscopic evaluation is essential for the initial identification of herbs, identifying small fragments of crude or powdered herbs, identifying [[Adulterant|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.<ref>{{Cite book |last1=Shah |first1=Biren |url=https://books.google.com/books?id=obWBB_-ke38C |title=Textbook of Pharmacognosy and Phytochemistry - E-Book |last2=Seth |first2=Avinash |date=2012-05-14 |publisher=Elsevier Health Sciences |isbn=978-81-312-3260-6 |language=en}}</ref>

The stomatal index is the percentage formed by the number of [[Stoma|stomata]] divided by the total number of [[epidermal cells]], with each stoma being counted as one cell.

<math>S.I.= \frac{S}{E+S}\times100</math>

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.<ref>{{Cite web |title=Stomatal Index Calculator {{!}} Calculate Stomatal Index |url=https://www.calculatoratoz.com/en/stomatal-index-calculator/Calc-42815 |access-date=2024-05-17 |website=www.calculatoratoz.com |language=en}}</ref>

== See also ==
* [[Bioprospecting]]
* [[List of plants used in herbalism]]
* ''[[Pharmacognosy Reviews]]''

== References ==
{{Reflist}}

== External links ==
* {{Commons category-inline}}

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