Prof. Dr. Amani S. Awaad

Professor of PharmacognosyPharmacognosy Department,

College of Pharmacy Salman Bin Abdulaziz

University,

Al-Kharj. KSA.

Email: amaniawaad@hotmail.com

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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3/7/2011 10

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

3/21/2011 46

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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