prof. dr. amani s. awaad - psau · pdf fileprof. dr. amani s. awaad ... bark of certain...
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Prof. Dr. Amani S. Awaad
Professor of PharmacognosyPharmacognosy Department,
College of Pharmacy Salman Bin Abdulaziz
University,
Al-Kharj. KSA.
Email: [email protected]
Drug Discovery and
Development
PHG 311
Drug Discovery from
Nature resources
Drug discovery:
Finding a lead
Drug
Discovery
from Nature
To recognize the type of natural drugs l?
To know what is natural drugs from plant
to learn how to obtain natural compounds
from natural recourses.
To understand roll of natural products
types in drug discovery
6
The Drug Discovery Process cont..
1-Drugs from plants
* Medicinal plants have been used as a major source
of drugs for thousands of years in human history, and
even today they are basis of the systematic traditional
medicine practices in many countries all over the world.
It is evident that the modern drug industry has been developed to a
considerable degree as a result of plant-based traditional medicines.
A review published in 2001 indicated that 88 active
compounds isolated from 72 medicinal plants have been introduced
into modern drug therapy, with many of them being considered as
the active principle responsible for their ethno pharmacological use.
Drug Discovery from Nature resources
7
The Drug Discovery Process cont..
1-Drugs from plants
Bases of plant Selection:
* Biodiversity Prospective:
The number and variety of plants found within a specified geographic region.
* Screening as much samples as possible for specified biological activities.
* Collect as much as possible. About 5- 15% from plant species were
screened. Estimated 300,000 to 500,000 are present.
* Ethnobotany (Ethnopharmacology) Prospective:
In this approach drug discovery is guided by the impressive quantity and
quality of information of indigenous cultures that have used plants and animal
products to control disease and injury.
This information is passed from generation to generation through oral history
and it is necessary to record and validate the knowledge of the shaman before it is
lost forever. Collection based on Folk uses of samples
Drug Discovery from Nature resources
Biological screening
Extraction
Solvent removal
In-vitro
In-vivo Isolation &identification
Flow Chart for drug
discovery from
The plant
plant IdentificationPlant collectionDry and grind
Drug Discovery from Nature resources
Examples of drugs derived
from plants:
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1-Drugs from plants
Morphine & Codeine
Morphine was first isolated in 1806 and
manufacturing of an analgesic drug was realized by E.
Merck , Germany in 1826.
Morphine is narcotic analgesic extracted from opium
which is obtained by incision of the capsules of the poppy.
Codeine (cough suppressant) Papaver somniferum
Heroin is a Synthetic derivatives of morphine
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1-Drugs from plants
Some of these plant-derived therapeutic agents, such as
atropine and Hyoscyamine from Atropa belladonna &
Hyoscyamus niger
Atropine and Hyoscyamine
Have the same structure – differ only in their
optical activity Also have different physiological
actions
Atropine: dilates eye pupils, decreases sweating,
produces stomach acid and saliva & relaxes
smooth muscle (asthma and colic).
Hyoscyamine: (also known as daturine) sometimes
known as levo-atropine
Hyoscyamus niger Atropa belladonna
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1-Drugs from plantsQuinine
• Quinine.
Quinine was isolated as pure
active principle as antimalaria in
1820, representing the only active
antimalaria medicine until the
introduction of the synthetic drug
pamaquine, the later with severe
side effects
Bark of certain Cinchona species
(Quinine, Quinidine, Cinchonine,
Cinchonidine).
N
NH
CH3
N
CH3
CH3
H3CO
Quinine.
pamaquine
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The bark of Willow-tree(Salix alba) was known for its analgesic and antipyretic properties for
more than 2000 years by Greeks and the Roman.
In 1850’s Salicin was isolated as the active principle of the bark, salicin ( beta glucoside of
salicylic alcohol).
Degradation of Salicin led to the discovery of Salicylic acid as analgesic and antipyretic. It was
commercialized in 1859.
Due to the gastric disorders of salicylic, efforts to reduce the side effects resulted in
acetylsalicylic acid which was introduced to the market under the trade name Aspirin in 1899 .
Acetylsalicylic acid. 1-Drugs from plants
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1-Drugs from plantsAnticancer drugs from plants
The example of anticancer drugs taxol was discovered at the
US National Center Institute in the late 1960s in the course of
an in vitro antitumor drug discovery program using human
tumor cell lines.
Screening of more than 110,000 samples derived from more
than 35,000 plant genera collected worldwide resulted in the
isolation and structure elucidation of taxol from the bark of
the North American yew tree (bark of Pacific Yew)
Taxus brevifolia
Taxol
Taxotere
Administered as a one-hour infusion every three weeks generally
over a ten cycle course, docetaxel is considered as or more effective
than doxorubicin, paclitaxel and fluorouracil as a cytotoxic
antimicrotubule agent.
Docetaxel is marketed worldwide under the name Taxotere by
Sanofi-Aventis. Annual sales approx $2bn. Patent expires in 2010.
Drug Discovery from Nature resources
Drugs from Microorganisms
Drug Discovery from Nature resources
Microorganisms such as bacteria and fungi
have been invaluable for discovering drugs and
lead compounds. These microorganisms produce
a large variety of antimicrobial agents which
have evolved to give their hosts an advantage
over their competitors in the microbiological
world.
The screening of microorganisms became
highly popular after the discovery of penicillin.
Soil and water samples were collected from all
over the world in order to study new bacterial or
fungal strains, leading to an impressive arsenal
of antibacterial agents
2-Drugs from Microorganisms
Drug Discovery from Nature resources
It was realized that microorganisms such as actinomycetes
and fungi not only produce secondary metabolites that affect
cell growth but also accumulate bioactive principles that interact
with valuable targets of cell metabolism
The discovery of penicillin in 1928 by Alexander Fleming and
its introduction in 1940/41 as an efficient antibacterial therapeutic
without side effects revolutionized medicinal chemistry and
pharmaceutical research by stimulating completely new strategies
in industrial drug discovery.
2-Drugs from Microorganisms
Penicillin G
Penicillin was discovered by chance from the culture broth
of Penicillium notatum as a bioactive principle inhibiting
growth of gram positive bacteria.
Drug Discovery from Nature resources
* The success of penicillin in treating infection led to an expansion
in the area of drug discovery from microorganisms.
* Microorganisms are a plentiful source of structurally diverse
bioactive substances, and have provided important contributions to the
discovery of antibacterial agents including penicillins, cephalosporins,
aminoglycosides, tetracyclines, and polyketides.
* Current therapeutic applications of metabolites from
microorganisms have expanded into immunosuppressive agents (eg,
cyclosporins and rapamycin), cholesterol-lowering agents (eg,
lovastatin and mevastatin), an antidiabetic agent (acarbose), and anti
cancer agents (eg, pentostatin, peplomycin, and epirubicin).
2-Drugs from Microorganisms
Drug Discovery from Nature resources
Biological screening
Matt
Extraction
Solvent removal
In-vitro
In-vivo Isolation &identification
Flow Chart for drug
discovery from
The microorganism
Broth
Extraction
Row extract
Drug Discovery from Nature resources
Acarbose (PRECOSE®)is is an oral alpha-glucosidase
inhibitor for use in the management of type 2 diabetes mellitus. Acarbose
is an oligosaccharide which is obtained from fermentation processes of a
microorganism, Actinoplanes utahensis
Acarbose was discovered in the target-directed screening from
culture broth of neglected genera of actinomycetes called Actinoplanes sp.
by researchers at the German company Bayer in 1970s.
Acarbose mechanism of action: inhibits enzymes (glycoside
hydrolase) needed to digest carbohydrates, it is an inhibitor of alpha
glycosidase, an enteric enzyme that releases glucose from larger
carbohydrates. So its competitive inhibition of the intestinal enzymatic
hydrolysis of oligosaccharides
2-Drugs from Microorganisms
a) Antidiabetic Drgus
Drug Discovery from Nature resources
2-Drugs from Microorganisms
b) Immune suppressant drug
Cyclosporin A was identified as an
antifungal agent now it is an
immunosuppressant drug widely used in
organ transplantation to prevent rejection. It
reduces the activity of the immune system by
interfering with the activity and growth of T
cells.It
was initially isolated from the fungus
Tolypocladium inflatum (Beauveria nivea),
found in a soil sample obtained in 1969 from
Hardangervidda, Norway, by Hans Peter
Frey, a Sandoz biologist
Drug Discovery from Nature resources
2-Drugs from Microorganisms
b) Anticancer drug
Several compounds derived from the screening
of culture broths from microorganisms towards
anticancer drugs are in preclinical or clinical
trials to study their therapeutic value. Examples
are the extremely toxic enediynes from
actinomycetes
Neocarzinostatin
Drug Discovery from Nature resources
Drugs from Marine
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* Unlike the long-standing historical medical
uses of terrestrial plants, marine organisms have a
shorter history of utilization in the treatment and/or
prevention of human disease.
* sources In recent years, there has been a
great interest in finding pharmacologically active
nature products from marine sources. Coral,
sponges, fish, and marine microorganisms have a
wealth of biologically potent chemicals with
interesting inflammatory, antiviral, and anticancer
activity.
* The marine environment is frequently
recognized as the largest potential source of
biodiversity, and it is being increasingly searched
for novel chemicals with useful bioactivity.
3-Marine natural productsDrug Discovery from Nature resources
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3-Marine natural products
* In 2004, 716 new marine compounds were described
in the literature and a further 812 in 2005.
* The range of chemical diversity is staggering, as is
the range of organisms. Several marine-derived compounds
are in clinical trials, particularly as anti-cancer agents.
At least until the arrival of antibiotics such as
penicillin, streptomycin, and others, higher terrestrial plants
had certainly the strongest impact on drug discovery from
natural sources.
Oddly enough, even though the oceans cover over 70
% of the earth’s surface, they have only comparatively
recently attracted the serious attention of drug prospectors,
which is in sharp contrast to the important and long-
standing impact of the sea on human nutrition
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3-Marine natural products
Marine natural products chemistry began to focus on the
discovery of new potential drugs in 1951 when
Bergmann and Feeney reported on the isolation of the
unusual nucleosides spongouridin and spongothymidin
from the sponge Cryptotethya crypta, which served as
lead structures for antiviral drugs.
More than a decade later, the discovery of
prostaglandins in the Caribbean gorgonian Plexaura
homomalla. Also maitotoxin a water soluble polyether-
type neurotoxin produced by Gambierdiscus toxicus, it
cause death in mice when injected intraperitonally at
concentrations of 170 ng per kg.
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Marine compounds have also been found
to have other activities, including antibiotic
and anti-inflammatory effects.
* The peptide ziconotide, a synthetic
version of the conotoxin M-VII A discovered
in the venom of a cone snail, was recently
brought to the market for treating patients with
severe chronic pain.
* Ziconotide is a highly specific blocker
of the calcium ion channels that are involved
in the transmission of pain signals in the spinal
cord.
3-Marine natural productsDrug Discovery from Nature resources
Drug from Animal sources
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Epibatidine
4-Drug from Animal sources
Animals can sometimes be a source of new lead compounds.
For example, a series of antibiotic peptides were extracted from
the skin of the African clawed frog and a potent analgesic
compound called epibatidine was obtained from the skin
extracts of the Ecuadorian frog
Animal can sometimes be a source of new pharmacologically
active nature products.
Human Insulin To treat diabetes Source of insulin: pancreas of
slaughtered pigs and cattle
Pepsin : Pepsin is protolytic enzyme obtained from the
glandular layer of the fresh stomach of the hog, Sus scrofa
Linne var. domesticus Gray
Drug Discovery from Nature resources
Drug from Venoms and toxins
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Venoms and toxins from animals, plants, snakes, spiders,
scorpions and insects are extremely potent because they
often have very specific interactions with a macromolecular
target in the body. Many of these toxins are polypeptides
(e.g. α-bungarotoxin from cobras). However, non-peptide
toxins such as tetrodotoxin from the puffer fish, puffer are
also extremely potent.
5-Venoms and toxins
Animal toxins are the source of an extraordinary array of
medications: 20 drugs to treat, for example, heart attacks
(INTEGRILIN®, AGGRASTAT®), high blood pressure
(CAPTOPRIL®), diabetes (BYETTA®), and cancer and
HIV pain (PRIALT®).
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Venoms and toxins from animals, plants, snakes, spiders,
scorpions and insects are extremely potent because they
often have very specific interactions with a macromolecular
target in the body. Many of these toxins are polypeptides
(e.g. α-bungarotoxin from cobras). However, non-peptide
toxins such as tetrodotoxin from the puffer fish, puffer are
also extremely potent.
Also it have been used as lead compounds in the
development of novel drugs. teprotide, a peptide isolated
from the venom of the Brazilian viper, was the lead
compound for the development of the antihypertensive
agents capotril
5-Venoms and toxins
Drug Discovery from Nature resources
the Designer Toxin technology holds potential for an
even wider range of illnesses since animal venoms have a
large variety of targets.
Specifically, toxin libraries can be employed to:
•identify new leads for drug development,
•improve existing drugs or drug leads,
•validate therapeutic targets.
Also it have been used as lead compounds in the development
of novel drugs. teprotide, a peptide isolated from the venom of
the Brazilian viper, was the lead compound for the development
of the antihypertensive agents capotril
5-Venoms and toxins
Drug Discovery from Nature resources
Mixed resources
Tissue cultures
Drug Discovery from Nature resources
What is tissue culture?
It is a technique of growing cells, tissues, organs
or whole organism in vitro (in glass) on artificial
culture medium under aseptic and controlled
conditions
Types of tissue culture
1. plant tissue culture
2. Animal tissue culture
6-Mixed resources
Tissue cultures
Drug Discovery from Nature resources
6-Mixed resources
(Tissue cultures)
Background
Tissue culture had its origins at the
beginning of the 20th century with
the work of Gottleib Haberlandt
(plants) and Alexis Carrel (animals)
Haberlandt
Carrel
Drug Discovery from Nature resources
6-Mixed resources
(Tissue cultures)
Tissue culture, both plant and animal has several critical
requirements
What is needed?
1-Appropriate tissue (some tissues culture better than others)
2-A suitable growth medium containing energy sources and inorganic saltsto supply cell growth needs. This can be liquid or semisolid
3-Aseptic (sterile) conditions, as microorganisms grow much morequickly than plant and animal tissue and can over run a culture
4-Growth regulators - in plants, both auxins & cytokinins. In animals, this
is not as well defined and the growth substances are provided in serum
from the cell types of interest
5-Frequent subculturing to ensure adequate nutrition and to avoid the
build up of waste metabolites
Drug Discovery from Nature resources
Mixed resources(Tissue cultures)
Types of tissue culture1-Plant tissue culture
Plant tissue culture is a collection of techniques used to maintain or
grow plant cells, tissues or organs under sterile conditions on a
nutrient culture medium of known composition. Plant tissue culture is
widely used to produce clones of a plant in a method known as
micropropagation
Culturing steps
Drug Discovery from Nature resources
Mixed resources(Tissue cultures)
Types of tissue culture1-Plant tissue culture
1.To produce many copies of the same plants with better flowers, odors, fruits or any
other properties.
2.To produce plants anytime we want although the climates are not appropriate.
3.it is possible to produce a new plant without infection.
4.Very helpful in the genetically modified organism studies.
5.Very useful solution for the prevention of starvation in third world countries it is
possible to produce more than one thousand of the same plant with higher productive
if its genome changed.
Why we use plant tissue culture?
Since production of secondary metabolites is generally higher in
differentiated tissues, there are attempts to cultivate shoot cultures
and root cultures for the production of medicinally important
compounds, these organ cultures are relatively more stable .
There are a number of medicinal plants whose shoot
cultures have been studied for metabolites.
Similarly, root cultures are valuable sources of medicinal
compounds, root systems of higher plants generally exhibit slower
growth and are difficult to harvest.
Drug Discovery from Nature resources
Plant species Product Reference
Artemisia Annua Artemesinin Park et al. (1989)
Atropa Belladonna Atropine Benjamin et al. (1987)
Catharanthus Roseus Vindoline Staba and Chung (1981)
Cinchona spp. Vinblastine Krueger et al. (1982)
Digitalis purpurea Cardenolides Hagimori et al . (1982a b)
Pelargonium tomentosum Essential oils Charlwood (1988)
Withania somniferum Withanolides Heble (1985)
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Shoot cultures of medicinal plants
Drug Discovery from Nature resources
Mixed resources(Tissue cultures)
Types of tissue culture
2-Animal tissue culture
Cell culture is the process by which
cells are grown under controlled
conditions, generally outside of their
natural environment. In practice, the
term "cell culture" now refers to the
culturing of cells derived from multi-
cellular eukaryotes, especially animal
cells
Drug Discovery from Nature resources
Culturing steps
Animal tissue is obtained either from a particular specimen, or from a ‘tissue bank’ of cryo-preserved (cryo = frozen at very low temperatures in a special medium)
Establishment of the tissue is accomplished in the required
medium under aseptic conditions
Growing the cells / tissue requires an optimum temperature, and subculturing when required
Human cells, for example are grown at 37degrees and 5% CO2
Mixed resources(Tissue cultures)Types of tissue culture
2-Animal tissue culture Drug Discovery from Nature resources
Mixed resources(Tissue cultures)Types of tissue culture
2-Animal tissue culture
• Growing viruses - these require living
host cells
• Making monoclonal antibodies, used
for diagnosis and research
• Studying basic cell processes
• Genetic modification & analysis
• Knockout’ technology - inactivating
certain genes and tracing their effects
• Providing DNA for the Human
Genome Project (and other species’
genome projects).
Uses of Animal Tissue Culture
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Natural product drug discovery limitations when compared
to synthetic chemical drug discovery
1- Building up and maintaining a high-quality natural product
library requires a skill set that is not generally available in
industry.
2- Natural products are often synthesized in small quantities and
present as mixtures in extracts, which require labor-intensive
and time consuming purification procedures
Drug Discovery from Nature resources
Limitations of Natural product drug
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Drug Discovery from Nature resources
Limitations of Natural product drug
3- Rediscovery of known compounds is a major problem
when screening natural product libraries. This is caused by a
lack of efficient dereplication methodologies for both natural
product sourcing and compounds in the natural product
libraries.
4-The time-consuming processes of de-replication and
purification are not compatible with the present regime of
screening campaigns in which assay support is only available
for a limited duration (three months).
5- Natural products are often structurally complex.
Modification of complex natural products using organic
chemistry is frequently challenging.
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Drug Discovery from Nature resources
Limitations of Natural product drug
Advances in natural product research to address these limitations
* Recent technological advances and the development of new
methods have revolutionized the screening of natural products
and offer a unique opportunity to re-establish natural products
as major source of drug leads.
* The new methods and technologies can address the
aforementioned limitations of screening of natural products.
Examples of recent advances in the application of these technologies
that have immediate impact on the discovery of novel drugs are:
•Development of a streamlined screening process for natural products.
•Improved natural product sourcing; and advances, Organic synthetic
methodologies; combinatorial biosynthesis; microbial genomics.
Pharmacodynamics:
The study of the effect of a drug and its mechanism of
action.
In cerebro:
Defined as: using ones own mind (knowledge) to think
through a problem, interpret data, or make conclusions.
In silico:
The use of software to analyze data or make prediction
(estimations) through some form of logic or knowledge
(learning rules or database).
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