Tannins are high molecular weight phenolic compounds that can precipitate proteins. They are classified as hydrolysable tannins, condensed tannins, and complex tannins. Tannins are found in plants and have properties such as astringency. They have traditional medical uses as styptics and protectants. Tannins also have economic importance in industries like leather production and ink manufacturing.
This slide contains sources, collection process, constituents and uses of some important plants for making medicine containing anthraquinone glycosides like Senna, Cascara Sagrada, Aloe, Rhubarb, Chrysarobin.
This slide contains sources, collection process, constituents and uses of some important plants for making medicine containing anthraquinone glycosides like Senna, Cascara Sagrada, Aloe, Rhubarb, Chrysarobin.
This slide includes the plants containing Volatile oil, their chemical components, Structures and uses. As well as how the volatile oil is being obtained from different methods and techniques with the pictorial representation.
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. Many such plant glycosides are used as medications. In animals and humans, poisons are often bound to sugar molecules as part of their elimination from the body.A glycoside is a molecule consisting of a sugar and a non-sugar group, called an aglycone. The sugar group is known as the glycone and can consist of a single sugar group or several sugar groups. The sugars is in its cyclic form and is covalently attached to the aglycon through the hydroxyl group of the hemiactal function.
There are many different kinds of aglycones. It can be a terpene, a flavonoid, a coumarin or practically any other natural occurring product (se figure 1)
The glycone can be attached to the aglycon in many different ways. The most common bridging atom is oxygen (O-glycoside), but it can also be sulphur (S-glycoside), nitrogen (N-glycoside) or carbon (C-glycoside). In general, one distinguishes between α-Glycosides and β-glycosides, depending on the configuration of the hemiactal hydroxyl group. The majority of the naturally occurring glycosides are β-glycosidesGenerally glycosides are more polar than the aglycones and as a result glycoside formation usually increases water solubility. This may allow the producing organism to transport and store the glycoside more efficiently
Many biologically active compounds are glycosides. The pharmacological effects are largely determined by the structure of the aglycone.
Glycosides comprise several important classes of compounds such as hormones, sweeteners, alkaloids, flavonoids and antibiotics
1) BASED ON THE CHEMICAL NATURE OF NON SUGAR MOIETY
2) BASED ON TE NATURE OF SUGAR MOITY
3) BASED ON LINKAGE BETWEEN GLYCON AND AGLYCON PORTION
4) BASED ON THERAPEUTIC NATURE OF GLYCOSIDE
Unit II Introduction to secondary metabolite
Phenylpropanoids and Flavonoids: Lignans, Tea, Ruta
For video lecture join to youtube channel snehal chakorkar
Alkaloids are a group of naturally occurring chemical compounds that contain mostly basic nitrogen atoms. This group also includes some related compounds with neutral and even weakly acidic properties. Some synthetic compounds of similar structure are also termed alkaloids. In addition to carbon, hydrogen and nitrogen, alkaloids may also contain oxygen, sulfur and, more rarely, other elements such as chlorine, bromine, and phosphorus.
Alkaloids are produced by a large variety of organisms including bacteria, fungi, plants, and animals. They can be purified from crude extracts of these organisms by acid-base extraction. Alkaloids have a wide range of pharmacological activities including antimalarial (e.g. quinine), antiasthma (e.g. ephedrine), anticancer (e.g. homoharringtonine),cholinomimetic (e.g. galantamine), vasodilatory (e.g. vincamine), antiarrhythmic (e.g. quinidine), analgesic (e.g. morphine),antibacterial (e.g. chelerythrine), and antihyperglycemic activities (e.g. piperine). Many have found use in traditional or modern medicine, or as starting points for drug discovery. Other alkaloids possess psychotropic (e.g. psilocin) and stimulant activities (e.g. cocaine, caffeine, nicotine, theobromine), and have been used in entheogenic rituals or as recreational drugs. Alkaloids can be toxic too (e.g. atropine, tubocurarine). Although alkaloids act on a diversity of metabolic systems in humans and other animals, they almost uniformly evoke a bitter taste
Isolation, Identification and Analysis of PhytoconstituentsDr. Siddhi Upadhyay
Isolation, Identification and Analysis of Phytoconstituents
a) Terpenoids: Menthol, Citral, Artemisin
b) Glycosides: Glycyrhetinic acid & Rutin
c) Alkaloids: Atropine,Quinine,Reserpine,Caffeine
d) Resins: Podophyllotoxin, Curcumin
This slide includes the plants containing Volatile oil, their chemical components, Structures and uses. As well as how the volatile oil is being obtained from different methods and techniques with the pictorial representation.
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. Many such plant glycosides are used as medications. In animals and humans, poisons are often bound to sugar molecules as part of their elimination from the body.A glycoside is a molecule consisting of a sugar and a non-sugar group, called an aglycone. The sugar group is known as the glycone and can consist of a single sugar group or several sugar groups. The sugars is in its cyclic form and is covalently attached to the aglycon through the hydroxyl group of the hemiactal function.
There are many different kinds of aglycones. It can be a terpene, a flavonoid, a coumarin or practically any other natural occurring product (se figure 1)
The glycone can be attached to the aglycon in many different ways. The most common bridging atom is oxygen (O-glycoside), but it can also be sulphur (S-glycoside), nitrogen (N-glycoside) or carbon (C-glycoside). In general, one distinguishes between α-Glycosides and β-glycosides, depending on the configuration of the hemiactal hydroxyl group. The majority of the naturally occurring glycosides are β-glycosidesGenerally glycosides are more polar than the aglycones and as a result glycoside formation usually increases water solubility. This may allow the producing organism to transport and store the glycoside more efficiently
Many biologically active compounds are glycosides. The pharmacological effects are largely determined by the structure of the aglycone.
Glycosides comprise several important classes of compounds such as hormones, sweeteners, alkaloids, flavonoids and antibiotics
1) BASED ON THE CHEMICAL NATURE OF NON SUGAR MOIETY
2) BASED ON TE NATURE OF SUGAR MOITY
3) BASED ON LINKAGE BETWEEN GLYCON AND AGLYCON PORTION
4) BASED ON THERAPEUTIC NATURE OF GLYCOSIDE
Unit II Introduction to secondary metabolite
Phenylpropanoids and Flavonoids: Lignans, Tea, Ruta
For video lecture join to youtube channel snehal chakorkar
Alkaloids are a group of naturally occurring chemical compounds that contain mostly basic nitrogen atoms. This group also includes some related compounds with neutral and even weakly acidic properties. Some synthetic compounds of similar structure are also termed alkaloids. In addition to carbon, hydrogen and nitrogen, alkaloids may also contain oxygen, sulfur and, more rarely, other elements such as chlorine, bromine, and phosphorus.
Alkaloids are produced by a large variety of organisms including bacteria, fungi, plants, and animals. They can be purified from crude extracts of these organisms by acid-base extraction. Alkaloids have a wide range of pharmacological activities including antimalarial (e.g. quinine), antiasthma (e.g. ephedrine), anticancer (e.g. homoharringtonine),cholinomimetic (e.g. galantamine), vasodilatory (e.g. vincamine), antiarrhythmic (e.g. quinidine), analgesic (e.g. morphine),antibacterial (e.g. chelerythrine), and antihyperglycemic activities (e.g. piperine). Many have found use in traditional or modern medicine, or as starting points for drug discovery. Other alkaloids possess psychotropic (e.g. psilocin) and stimulant activities (e.g. cocaine, caffeine, nicotine, theobromine), and have been used in entheogenic rituals or as recreational drugs. Alkaloids can be toxic too (e.g. atropine, tubocurarine). Although alkaloids act on a diversity of metabolic systems in humans and other animals, they almost uniformly evoke a bitter taste
Isolation, Identification and Analysis of PhytoconstituentsDr. Siddhi Upadhyay
Isolation, Identification and Analysis of Phytoconstituents
a) Terpenoids: Menthol, Citral, Artemisin
b) Glycosides: Glycyrhetinic acid & Rutin
c) Alkaloids: Atropine,Quinine,Reserpine,Caffeine
d) Resins: Podophyllotoxin, Curcumin
A comprehensive presentation about tannin , tannin yielding plants and plant parts from where they are obtained.
Use full for forestry students and others who want to know about non wood forest products.
It is a secondary metabolite ,it can present in all trees and plant can sows astringent and antioxidant property is known as tannin.
A tannin (also known as vegetable tannin, natural organic tannins or sometimes tannoid, i.e. a type of biomolecule, as opposed to modern synthetic tannin)
is an astringent, bitter plant polyphenolic compound that binds to and precipitates proteins and various other organic compounds including amino acids and alkaloids.
The term tannin (from tanna, an Old High German word for oak or fir tree, as in Tannenbaum) refers to the use of wood tannins from oak in tanning animal hides into leather;
Tannins are a class of astringent, polyphenolic biomolecules that bind to and precipitate proteins and various other organic compounds including amino acids and alkaloids. The term tannin refers to the use of oak and other bark in tanning animal hides into leather.
Hey,
I am a B.Pharma. student. This is my personal notes on the topic called Tannins, a topic from Unit 2 i.e. Secondary metabolites from the subject Pharmacognosy and Phytochemistry II from Semester 5th. Syllabus of this subject is according to GTU. Hope this will be much helpful for your reading.
Thank you.
the topic tannins include their introductory part, definition, physical properties, uses, importance, classification of tannins, identification test for tannins, and the drug containing tannins
This ppt contains a suitable contents. This notes is effective for B.Pharm & D.Pharm students. In this notes we all the related topic of secondary metabolites. In this notes we all sub topics of secondary metabolites such as Alkaloids, Glycosides, Terpenoids, Taninns, Resins, Flavonoids, etc.
Mass- 3rd lecture
Ionization methods
Electron Impact (EI),
Chemical Ionization (CI),
Field Desorption (FD),
Fast Atom Bombardment (FAB),
Plasma Desorption (PD),
Matrix assisted laser desorption (MALDI),
Thermospray Mass and
Electrospray(ESI)
Analysis techniques
Magnetic Sector
Quadrupole
Ion Trap
Time-of-Flight (TOF)
Fourier Transform (FT)
Richard's entangled aventures in wonderlandRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
Professional air quality monitoring systems provide immediate, on-site data for analysis, compliance, and decision-making.
Monitor common gases, weather parameters, particulates.
Nutraceutical market, scope and growth: Herbal drug technologyLokesh Patil
As consumer awareness of health and wellness rises, the nutraceutical market—which includes goods like functional meals, drinks, and dietary supplements that provide health advantages beyond basic nutrition—is growing significantly. As healthcare expenses rise, the population ages, and people want natural and preventative health solutions more and more, this industry is increasing quickly. Further driving market expansion are product formulation innovations and the use of cutting-edge technology for customized nutrition. With its worldwide reach, the nutraceutical industry is expected to keep growing and provide significant chances for research and investment in a number of categories, including vitamins, minerals, probiotics, and herbal supplements.
(May 29th, 2024) Advancements in Intravital Microscopy- Insights for Preclini...Scintica Instrumentation
Intravital microscopy (IVM) is a powerful tool utilized to study cellular behavior over time and space in vivo. Much of our understanding of cell biology has been accomplished using various in vitro and ex vivo methods; however, these studies do not necessarily reflect the natural dynamics of biological processes. Unlike traditional cell culture or fixed tissue imaging, IVM allows for the ultra-fast high-resolution imaging of cellular processes over time and space and were studied in its natural environment. Real-time visualization of biological processes in the context of an intact organism helps maintain physiological relevance and provide insights into the progression of disease, response to treatments or developmental processes.
In this webinar we give an overview of advanced applications of the IVM system in preclinical research. IVIM technology is a provider of all-in-one intravital microscopy systems and solutions optimized for in vivo imaging of live animal models at sub-micron resolution. The system’s unique features and user-friendly software enables researchers to probe fast dynamic biological processes such as immune cell tracking, cell-cell interaction as well as vascularization and tumor metastasis with exceptional detail. This webinar will also give an overview of IVM being utilized in drug development, offering a view into the intricate interaction between drugs/nanoparticles and tissues in vivo and allows for the evaluation of therapeutic intervention in a variety of tissues and organs. This interdisciplinary collaboration continues to drive the advancements of novel therapeutic strategies.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
Seminar of U.V. Spectroscopy by SAMIR PANDASAMIR PANDA
Spectroscopy is a branch of science dealing the study of interaction of electromagnetic radiation with matter.
Ultraviolet-visible spectroscopy refers to absorption spectroscopy or reflect spectroscopy in the UV-VIS spectral region.
Ultraviolet-visible spectroscopy is an analytical method that can measure the amount of light received by the analyte.
This pdf is about the Schizophrenia.
For more details visit on YouTube; @SELF-EXPLANATORY;
https://www.youtube.com/channel/UCAiarMZDNhe1A3Rnpr_WkzA/videos
Thanks...!
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
Introduction:
RNA interference (RNAi) or Post-Transcriptional Gene Silencing (PTGS) is an important biological process for modulating eukaryotic gene expression.
It is highly conserved process of posttranscriptional gene silencing by which double stranded RNA (dsRNA) causes sequence-specific degradation of mRNA sequences.
dsRNA-induced gene silencing (RNAi) is reported in a wide range of eukaryotes ranging from worms, insects, mammals and plants.
This process mediates resistance to both endogenous parasitic and exogenous pathogenic nucleic acids, and regulates the expression of protein-coding genes.
What are small ncRNAs?
micro RNA (miRNA)
short interfering RNA (siRNA)
Properties of small non-coding RNA:
Involved in silencing mRNA transcripts.
Called “small” because they are usually only about 21-24 nucleotides long.
Synthesized by first cutting up longer precursor sequences (like the 61nt one that Lee discovered).
Silence an mRNA by base pairing with some sequence on the mRNA.
Discovery of siRNA?
The first small RNA:
In 1993 Rosalind Lee (Victor Ambros lab) was studying a non- coding gene in C. elegans, lin-4, that was involved in silencing of another gene, lin-14, at the appropriate time in the
development of the worm C. elegans.
Two small transcripts of lin-4 (22nt and 61nt) were found to be complementary to a sequence in the 3' UTR of lin-14.
Because lin-4 encoded no protein, she deduced that it must be these transcripts that are causing the silencing by RNA-RNA interactions.
Types of RNAi ( non coding RNA)
MiRNA
Length (23-25 nt)
Trans acting
Binds with target MRNA in mismatch
Translation inhibition
Si RNA
Length 21 nt.
Cis acting
Bind with target Mrna in perfect complementary sequence
Piwi-RNA
Length ; 25 to 36 nt.
Expressed in Germ Cells
Regulates trnasposomes activity
MECHANISM OF RNAI:
First the double-stranded RNA teams up with a protein complex named Dicer, which cuts the long RNA into short pieces.
Then another protein complex called RISC (RNA-induced silencing complex) discards one of the two RNA strands.
The RISC-docked, single-stranded RNA then pairs with the homologous mRNA and destroys it.
THE RISC COMPLEX:
RISC is large(>500kD) RNA multi- protein Binding complex which triggers MRNA degradation in response to MRNA
Unwinding of double stranded Si RNA by ATP independent Helicase
Active component of RISC is Ago proteins( ENDONUCLEASE) which cleave target MRNA.
DICER: endonuclease (RNase Family III)
Argonaute: Central Component of the RNA-Induced Silencing Complex (RISC)
One strand of the dsRNA produced by Dicer is retained in the RISC complex in association with Argonaute
ARGONAUTE PROTEIN :
1.PAZ(PIWI/Argonaute/ Zwille)- Recognition of target MRNA
2.PIWI (p-element induced wimpy Testis)- breaks Phosphodiester bond of mRNA.)RNAse H activity.
MiRNA:
The Double-stranded RNAs are naturally produced in eukaryotic cells during development, and they have a key role in regulating gene expression .
2. Objectives:
1. Definition
2. Classification
3. General characters
4. Distribution and physiological role
5. Tests for identification
6. Quantitative determination
7. Medicinal and biological properties
8. Economic importance
3. Definition;
• They are high molecular weight phenolic compounds
capable of precipitation of animal proteins in hides and
converting them into leather. “Tanning Industry”
.
4.
5. They are condensation products of Gallic acid or
Flavan-3-ol as well as their glycosides.
Gallic acid Flavan-3-ol
7. True tannins
These are complex phenolic compounds of high
molecular weights ranging from about 1000 to 5000.
They display the general properties of tannins and
precipitated by gelatin in 1% solution.
True tannins can be sub-classified into hydrolysable
tannins, condensed tannins and complex tannins.
8. Hydrolysable tannins (pyrogallol tannins)
These may be hydrolyzed by acids or enzymes such as
tannase.
They are formed from several molecules of phenolic
acids such as gallic and hexahydroxydiphenic acids
which are united by ester linkages to a central sugar
(mainly glucose) molecule.
Like gallic acid their solutions turn blue with iron salts.
They were formerly known as pyrogallol tannins, because
on dry distillation gallic acid and similar components are
converted into pyrogallol.
Two principal types of hydrolysable tannins are
gallitannins and ellagitannins which are, respectively,
composed of gallic acid and hexahydroxydiphenic
acid units.
9. Tannaseis an enzyme that catalyzes the chemical reaction
digallate + H2O 2 gallate
This enzyme belongs to the family of hydrolases, specifically
those acting on carboxylic ester bonds. The systematic name
of this enzyme class is tannin acylhydrolase. Other names in
common use include tannase S, and tannin acetylhydrolase.
Tannase is a key enzyme in the degradation of gallotannins.
It is present in a diverse group of microorganisms,
including rumen bacteria
10. The difference between Ellagitannins and gallotannins
that; galloyl groups are linked through C-C bonds in ellagitannins,
whereas the galloyl groups in gallotannins are linked by depside
bonds.
A depside is a type of polyphenolic compound composed of two or
more monocyclic aromatic units linked by an ester bond.
Ellagic acid (the depside of Hexahydroxydiphenic acid) can arise
by lactonization during chemical hydrolysis of the tannin; thus, the
term ellagitannin is a misnomer.
C-glucosidic ellagitannins are common in a number of families
including the Myrtaceae, Hamamelidaceae, Punicaceae and
Ellagic acidHexahydroxydiphenic acid
13. Condensed tannins
(Catechol) (proanthocyanidins)
Unlike hydrolysable tannins, these are not readily
hydrolyzable to simpler molecules and they do not contain
a sugar moiety.
They are related to flavonoid pigments and have
polymeric flavan-3-ol structures (usually di- and trimers).
• On dry distillation they yield catechol and these
tannins are therefore sometimes called catechol
tannins.
• Like catechol itself, their solutions turn to green with
ferric chloride.
14. Catechins which also occur with the tannins and flavan-
3,4-diols (leucoanthocyanidins) are intermediates in the
biosynthesis of the polymeric molecules.
Stereochemical variations add to the variety of possible
structures.
On treatment with acids or enzymes condensed tannins
are converted into red insoluble compounds known as
phlobaphenes.
Phlobaphenes give the characteristic red color to many
drugs such as red cinchona bark, which contain these
phlobatannins and their decomposition products.
16. Complex tannins
These represent a group of tannins that are
biosynthesized from both hydrolysable tannin (mostly
a C-glucoside ellagitannin) (flavono-ellagitannin)and
condensed tannin.
19. Pseudotannins
Pseudotannins are polyphenolic compounds of lower molecular
weight than true tannins.
They do not respond to the goldbeater's skin test and may,
under certain conditions, e.g. in concentrated solutions, give
precipitates with gelatin and be partly retained by hide powder.
Examples are gallic acid, catechins and chlorogenic acid.
Chlorogenic acidCatechinGallic acid
20. Distribution
Type of tannin Plant name and organ
Hydrolysable tannins
Gallitannins
Ellagitannins
Rhubarb rhizome, clove buds, red rose petals, galls, hamamelis leaves and
chestnut bark.
Pomegranate rind and bark, eucalyptus leaves, myrobolans and oak bark.
Condensed tannins Barks: e.g. cinnamon, hamamelis and cinchona.
Roots and rhizomes: e.g. krameria and male fern.
Flowers: e.g. lime and hawthorn.
Seeds: e.g. cocoa, kola and areca.
Leaves: e.g. hamamelis, hawthorn and tea, especially green tea.
Extracts and dried juices: catechu and Indian kino.
Complex tannins Members of Fam. Combretaceae, Myrtaceae and Fagaceae.
Pseudotannins
Gallic acid
Catechins
Chlorogenic acid
Ipecacuanhic acid
Galls, rhubarb and most drugs that contain gallitannins.
Catechu, cocoa and most drugs containing condensed tannins.
Coffee particularly when unroasted.
Ipecacuanha.
21. Major sources of commercial tannins, for use in leather industry, are
obtained from chestnut bark trees.
Pharmaceutical tannin is prepared from oak galls.
Chestnut bark
Castalagin
Oak galls
Tannic acid
22. Physiological role
They exert an inhibitory effect on many enzymes due to protein
precipitation and, hence, may contribute a protective function in barks
and heartwoods.
• They play an important role in the mechanism of hydrogen transfer in
plant cells, probably due to their high affinity for oxygen.
• Certain drugs contain only one type of tannin. Others may contain
more than one type e.g. tea, hamamelis leaves and bark contain both
hydrolysable and condensed tannins.
23. Physical properties
Tannins are non-crystallizable compounds.
They are soluble in water forming colloidal solutions
with acidic reaction and sharp astringent taste.
They are soluble in dilute alkalis, alcohol, glycerol and
acetone, but only sparingly soluble in other organic
solvents.
Their solutions precipitate heavy metals, alkaloids,
glycosides and protein (e.g. gelatin).
24. Tests for identification
• Goldbeater's skin test (Skin tanning test):
Goldbeater's skin is a membrane prepared from the intestine of the ox
and behaves similar to an untanned hide.
Soak a small piece of goldbeater's skin in 25% HCl; rinse with distilled
water and place in the solution to be tested for 5 min. Wash with distilled
water and transfer to a 15 % solution of ferrous sulphate.
A brown or black color on the skin denotes the presence of true
tannins.
• Gelatin test:
Solutions of true tannins (about 0.5-1%) precipitate a 1% solution of
gelatin containing 10% sodium chloride.
Gallic acid and other pseudotannins may react in concentrated
solutions.
• Test with phenazone:
Add 0.5 g of sodium acid phosphate to about 5 ml of an aqueous extract
of the drug; warm, cool and filter. To the filtrate add 2 % phenazone
solution.
All tannins are precipitated, the precipitate being bulky and often
colored.
25. • Test with ferric chloride:
Add 5 % ferric chloride solution drop by drop to 2-3 ml of the extract and
observe the color produced.
Hydrolysable tannins (gallitannins and ellagitannins) give bluish-black color
or precipitate and condensed tannins brownish-green ones.
If the test is carried on an extract that contains both types of tannins, a blue
color is produced which changes to olive-green as more ferric chloride is
added.
• Test with bromine water:
Add bromine water to an aqueous extract of the drug.
- Condensed tannins gives a buff-colored precipitate
- Hydrolysable tannins do not form any precipitate.
• Test for catechin:
Catechins on heating with acids form phloroglucinol and they can be
detected by a modification of the well-known test for lignin.
Dip a matchstick in the plant extract containing catechin, dry, moisten with
concentrated HCl and warm near a flame a pink or red is produced.
• Test for chlorogenic acid:
Add aqueous ammonia to an extract containing chlorogenic acid, expose to
air a green color gradually develops.
26. Quantitative determination
1. Hide powder method:
This is the most widely used on commercial scale.
A known amount of a reference sample of hide powder is added to the
drug extract.
The difference in the dry weight of the extract before and after treatment
with hide powder is a measure for the tannin content.
1. Copper acetate method:
Tannin is precipitated quantitatively with copper acetate solution.
The precipitate of copper tannate is collected on an ashless filter paper,
washed with water till free from copper ions and ignited.
The residue of copper oxide obtained is completely oxidized by adding a
few drops of nitric acid.
Tannin content is calculated on the basis that 1 part of copper oxide is
equivalent to 1.305 parts of tannins.
27. • Agglutination method
This depends on that a suspension of red blood cells is agglutinated
with tannins, but haemolysis does not occur (c.f. saponins). The
erythrocytes are agglutinated (stick together) due to formation of a sticky
membrane on their surface in contact with tannins.
The quantity of red blood cells precipitated is proportional to the
amount of "astringent" tannin present.
The end point is reached when red blood cells are completely
precipitated i.e. the solution is colorless on shaking. Reaction is stopped
when the filtrate gives no precipitate with ferric chloride (this indicates
absence of tannins).
The astringency value of the extract is compared with that of tannic acid
used as reference standard, recorded as percentage tannic acid and
referred to as "tannin number".
All the solutions used should be isotonic.
Catechin is inactive.
• Iodometric determination
Tannins and pseudotannins quantitatively consume iodine from alkaline
medium due to their phenolic nature.
Excess iodine is determined by titration, after acidification, with standard
sodium thiosulphate solution using starch as indicator.
True tannins can be removed from the extract by precipitation with gelatin.
This can permit the determination of each group of constituents alone.
28. Medicinal and biological properties
Tannin-containing drugs precipitate proteins and have been traditionally
used as styptics (stop hemorrhage) and internally for the protection of
inflamed surfaces of mouth and throat.
They play an important role in the treatment of burns. They form a mild
antiseptic protective layer on the surface of the injured skin below which
regeneration of new tissue takes place.
They act as anti-diarrheals, although not recommended in this respect as
they usually delay elimination of bacterial toxins from the body.
Tannins have been employed as antidote in poisoning by heavy metals,
alkaloids and certain glycosides due to their precipitation as
tannates.
Recently tannins as most polyphenols were proved to have a potent
antioxidant effect.
29. Studies on the antitumor effect of tannins proved that a strong
activity is obtained with ellagitannins having galloyl groups at the O-
2 and O-3 positions of the glucose core(s), as in the
tellimagrandins.
Certain tannins were proved to have anti-HIV activities
Tellimagrandin II (Anti herpes virus)
30. Economic importance
Tannins are used in leather industry to transform raw animal skin to
leather due to their ability to cross-link with proteins. To be effective for
tannage, the polyphenol molecule must be neither too large as it will
be unable to enter the interstices between the collagen fibrils of the
animal skin nor too small as it will be unable to cross-link between the
protein molecules of adjacent fibrils at several points.
Tannins are used in the manufacture of inks based on the dark colored
complexes they form with iron salts.
Tannins are used in food industries to improve acceptance of many
beverages and foods when a degree of astringency is required.
31. Summary:
1. Definition
2. Classification
3. General characters
4. Distribution and physiological role
5. Tests for identification
6. Quantitative determination
7. Medicinal and biological properties
8. Economic importance