drying of crude_drugs(1)

Classification of Plant Drugs

Alphabetical

Taxonomic

Morphological

Pharmacological/Therapeutic

Chemical/Biogenic

Alphabetical Classification

Latin/vernacular names

Advantage: quick reference

Disadvantage: no indication of the

interrelationships between plants (drugs)

Used in

Dictionaries

Pharmacopoeias

Taxonomic Classification

Plants classified based on their botanical

classification

(Plant) Drugs are arranged according to the

plants they are derived from (class, order, family,

genera & species).

Advantage: Precise & ordered arrangement (no

ambiguity)

Disadvantage: Botanical knowledge decreases

over the years in students

< popular with teaching

Morphological Classifications

(Plant) Drugs are divided into organized and

unorganized drugs

Based on plant morphology

Advantage

Practical application to the study of plant drugs

Disadvantage

Microscopical studies are needed to identify

powdered herbs

Morphological Classification

Organized drugs Leaves

Flowers

Fruits

Seeds

Herbs

Whole organisms

Woods

Barks

Rhizomes

Roots

Unorganized drugs Dried latices

Extracts

Gums

Resins

Oils

Fats

waxes

Pharmacological/Therapeutic

Classification Plant drugs are grouped according to their

pharmacological action of the most important active constituent in the plant

OR

According to the drug’s therapeutic use

Disadvantage: The constituents of one drug may have more than one therapeutic action (fall into numerous groups. E.g. Flavonoids)

Biogenic/Chemical

Classification Drugs are classified according to the main active

chemical constituent available in the plant

OR

The biosynthetic pathways of the main active constituent.

Advantage: Popular for teaching when Pharmacognacy is phytochemically based.

Disadvantage: Ambiguities: Plants contain more than one group of active constituents each with different actions

Cultivation, Collection &

Preparation of Crude Drugs

Crude drugs cultivated or uncultured

plants

Some cases: pharmacopoeias specify

cultivated spp. Such as Fennel, ginger,

cinnamon & opium

Opium: only official growers may legally

produce herbs.

Other herbs: senna, tragacanth etc, may

be collected from wild or cultivated

species.

Disadvantages of Wild plant

Collection Sparse distribution e.g. Sceletium

tortuosum

Potentially difficult to transport herb to

area of processing

Difficult access (e.g. Forests, Mountains

etc)

Collector ignorance admixture of other

plants, collection of undesired plant parts

or stage of development or during an

incorrect season loss of medicinal

activity.

Advantages of Cultivated Herbs

Only desired spp are collected uniform

quality.

Collection, transport & access to

processing facilities is improved.

Better control of soil quality, pests & plant

disease.

Supply: Constant & Regular (Controlled)

Herb collectors - trained

Plant Variation

Ideally: correct cultivation & harvesting is aimed at producing high quality, healthy herbs.

Complicated: All natural products: variation between individual plants.

Plant size

Content of medicinal actives

WHAT BRINGS ABOUT THIS VARIATION?

Variation Factors

3 Groups

Environmental (Exogenous) Factors

Genetic (Endogenous) Factors

Post-Cultivation Factors (Drying & Storage

Methods etc)

Exogenous Factors

Climate

Altitude/Latitude

Collection Season

Soil Condition

Developmental Stage of the Plant

Plant Condition

Use of Growth-Promoting Substances

Allelopathy

Parasites

Effect of Climate

Plants should be cultivated in conditions which are similar to the plant’s natural habitat

Most herbs grow best in sunny, dry conditions

Factors affecting climate

Temperature

Rainfall

Day-length

Temperature

Major component

Affects both the growth/development

AND

Metabolism of the plant

Each plant is specialized to adapt to its native

environment

But most are able to exist in wide temperature

ranges.

E.g. Tropical & Sub-tropical plants in temperate

regions

Temperature: affects plant

chemical Reaction RatesE.g. Datura stramonium: lower alkaloids in

cloudy/rainy weather (winter).

E.g. Volatile oils are produced more

readily in warmer weather, yet very hot

days lead to a physical loss of oil

Growing peppermint in shade rather than the

sun.

Rainfall

Consider: annual rainfall, distribution, humidity effect, soil type. Especially NB for the production of volatile oils

May influence the production of glandular hairs

Continuous rainfall: loss/leaching of water-soluble substances through leaves & roots: glycosides, tannins & flavonoids & some volatile oils.

NB: over-watering

Day-length Amount & intensity of light needed differs

from herb-herb. Affects the amount of glycosides, alkaloids & volatile oils produced.

E.g. peppermint:

Long day: menthone, menthol & menthofuran traces

Short day: menthofuran = main component

Other spp: produce more active constituents at night

E.g. Nicotaina

Flowers: only produced under x day-lengths (NB where seeds are used

Radiation

Type of radiation plants receive = NB

E.g. Ocimum basilicum – plants grown in

glass houses have less phenols &

terpenoids in the leaves (flavonoids,

volatile oils).

E.g. Tomato

Latitude & Altitude

Gentian: bitter constituents increase with

altitude

Thyme & Peppermint: constituents decrease

with altitude

Other oil producing plants reach a maximum at x

altitudes.

Flower production is also affected by location

(altitude)

Fat/oil production may be influenced by

latitudes.

E.g. Peanut & olive trees grown in the subtropics

Collection Season Active constituents of herbs are affected

by the seasons (due to climate, rainfall,

day-length etc).

Medicinal plants should be therefore

collected in the season in which their

active constituents are highest.

E.g. Rhubarb (laxative) contains high

anthranol in winter. This is then oxidized

to anthroquinones in summer.

Soil Condition

Soil character, composition, permeability, porosity all effect the health of medicinal herbs.

E.g. Chalky soil poor Digitalis growth

Nutrient content of soils crop rotation

N2 – nitrates

Phosphate – bone

Potassium – wood ash

Ca – lime/egg shells

pH of soil affects inorganic compounds of soil

Developmental Age of Herb

Different components are produced in

varying amounts at different

developmental stages

Vitamin C Highest in rosehips just before

maturity

Camphor accumulates therefore collected

from older trees

Alkaloids highest in young seeds

Young cloves higher oil content than older

cloves

Herb Condition/Parasites

Certain other factors also influence the

quality of the herb.

E.g. Fungus on henbane lowers the

alkaloid content

It is therefore necessary to control pests

and disease which may affect herbs and

their medicinal value

Only possible when herbs are cultivated

Use of Growth-Promoting

Substances

Auxins

Gibberellins

Cytokinins

Auxins

EFFECTS

Cell elongation

Increase in stem

length

Promotion of

adventitious root

growth

Fruit setting in the

absence of pollination

USES

[low]

Accelerate the rooting

of woody cuttings

E.g. Trees raised from

cuttings instead of

seeds

[high]

Acts as a selective

herbicide or weed-killer

Gibberellins

Isolated from a Japanese rice fungus

Uses: initiates the synthesis of enzymes

needed for seed germination & seedling

establishment.

Cytokinins

Uses

Play an important role in cell division

Promote protein synthesis

Involved in bud differentiation

Allelopathy Definition: The constant effect which living

organisms exert on each other, which may

be either beneficial or harmful.

In Plants: different plants growing

together affect factors such as

Germination rate

Leaf development

Fruit maturation

Chemical constituents produced

Allelopathy Effects

Transmitted between plants in a number of

ways

Exhalation of leaves

Root secretions

Extractions from fallen leaves into the soil

Mutual dependant organisms (beneficial)

symbiosis

E.g. Urtica dioica (stinging nettle)

Destructive allelopathy antibiosis

E.g. Belladonna growth inhibited when

cultivated next to mustard

Other factors

Effects of Exogenous factors may affect plants growing in isolation differently than plants growing in communities

E.g. Camphor trees: produce < camphor when growing alone than those growing in groups.

Ergot: alkaloid content differs according to the host (specific rye spp or other type of cereal e.g. barley or oats)

Variation of actives

E.g. Foxglove produces more actives during the day than at night.

Endogenous Factors

Genetic differences are responsible for

Morphological variety

Biochemical diversity (amount & type of

chemicals produced)

Chemical races

Polyploidy Naturally occurring polyploidy

Mentha

Commercial crops (wheat, oats, cotton)

Artificially induced

Heat treated

Addition of Specific chemical agents

Effects: variety of changes

Plant size

Organ size

Individual cell size

Change in chemical constituent production

Effects of Polyploidy

BENEFICIAL Deadly nightshade

(Atropa belladonna)

X2 alkaloid than diploid

Papaver somniferum(opium poppy)

latex x2 morphine than diploid

Carum carvi(carraway)

yields < volatile oils than diploid

NON-BENEFICIAL

(Potential)

Reduced growth

Reduced plant vigour

Reduced plant fertility

Plant Breeding Methods

Influence morphological and chemical

variety in plants

Aimed at reducing variability of these factors

(naturally produced by genetic differences)

At producing plants with constant, desirable

characteristcs.

3 methods

Selection

Hybridization

Transgenic medicinal plants

Selective Breeding

Individual plants showing the most desirable

characteristics are chosen and interbred

2nd population: improved quality

Reason: even in a single species of plants

appearing identical, genetic varieties are

present making them slightly different from

each other

Result: improved growth rate

disease resistance

winter hardiness

increased yield of medicinal actives

Hybridisation

Mating of different spp or varieties to

produce a hybrid progeny, different from

both parents (incorporating desired

characteristics).

E.g. Mentha piperita & M. spicata are

naturally occuring hybrids.

Transgenic Medicinal Plants

Genetic Engineering: Recombinant DNA

Transfer DNA sequences from the

chromosomes of 1 plant to another

Lead to the artificial transfer of a particular

character from one organism to another

Plant Propagation

SEED

E.g. Digitalis

Rx of seed prior to sowing may influence germination

X plants need soaking before germination (H20/acid)

VEGETATIVELY

E.g. Bulb, tuber, rhizome

By division: plant separated from aerial stems/buds, each with roots & growing point

Runners: mint

Stolons: Liquorice

Cuttings

Grafting

Fermentation

Inoculation

Harvesting of Herbs

Roots & Rhizomes: collected when aerial

parts are dried down (if not – fleshy &

difficult to dry)

Bark: Damp weather

Aerial parts – at flowering (active

photosynthesis)

Flowers e.g. clove – before fully expanded

Fruits – vary

Fully ripe: Anise, Fennel

Nearly ripe: cardamoms (Before seed

dispersal)

Gums/Resins – dry weather

Preparation of Herbs Remove sand, stones

Washing underground parts

Remove rootlets, diseased portions

Slicing – larger organs (ginger)

Peeling – ginger/liqourice

Removal (e.g nux vormica – fruit pulp)

Packing into quills (cinnamon)

Grading (senna, gums)

Drying of Crude Drugs

Aim = removal of excessive moisture

Ensures good keeping

Prevent mould & bacterial growth

Prevent enzyme activity preventing

chemical changes

Ideally: herbs should be dried ASAP after

collection (maintains appearance &

chemical activity)

Drying Methods

Air Drying

Artificial Drying

Vacuum Drying

Air Drying

Sun Drying

When herbs are not adversely affected by excessive sunlight.

Dried in thin layers tuned over occasionally

E.g. clove, cardamom

Shade Drying

When sunlight causes discoloration & warping/shrivelling

E.g. cinnamon

Artificial Drying

Generally the most acceptable form of

drying herbs.

Rapid (less exposure to heat less

chances of chemical alteration)

Control temperature (normally 40ºC) &

ventilation (allows dry air to replace wet

air).

Vacuum Drying

Steam-heated ovens: pump used to

extract air

Low pressure to ensure rapid and

complete drying

Expensive method

Reserved for expensive herbs and which

cannot be sufficiently dried through other

methods.

General Drying Techniques:

Leaves

Leaves/Herbs:

40-50º C

Maintains good colour

Without overdrying herbs

Normally destalked first

Best dried for short periods of time only

prevents shrivelling and discolouration

Leaves may be bleached through the drying

process best dried in dark


Roots/Rhizomes

Washed

Sliced

Dried between 30-65ºC

Temperature too high: forms a tough crust

on the outside preventing the further

drying of deeper tissue

Thick organs may require long periods of

drying (10days-3weeks) to avoid mould

growth.


Flowers

Normally destalked before drying

Flowers may also be bleached when dried

best dried in dark.


Volatile oil containing herbs

Air-Dried at very low temperature

Avoid volatilization of oil contents

Should also be dried separately from other

herbs.


Fruits & Seeds

Normally partially dry before harvesting

May be air-dried afterwards

Seeds are normally separated from the

fruits before drying

Fruits are normally left whole

Some fruits (cardamom) rupture due to

excessive heat.


Bark

Occasionally requires the removal of the

outer layers

Which Drying Technique to choose

Depends on the

PHYSICAL CHARACTERISTIC OF THE

HERB

(mentioned earlier)

CHEMICAL CHARACTERISTIC OF THE

HERB

Chemical Nature of Herbs

Volatile Oils: (Thyme) Dried separately,

at low temperature

Starchy herbs (oats): gelatinize if

overheated

Alkaloids: become deactivated if dried

excessively at high temperatures (opium

poppy)

Changes occurring in herbs when

drying

Changes due to enzyme action

Oxidation

Volatilisation

Browining

Adulteration of Crude Drugs

Adulterant: herb which does not conform to official standards.

Usually practised when the herb is scarce or expensive

Effects of Adulteration Inferiority

Spoilage

Admixture

Sophistication

Deterioration

Substitution

Inferior Herb Quality Leads to a sub-standard herb

Results naturally (in nature)

Ignorance/carelessness

E.g. Collection of genuine material regardless of the time factor – collecting herbs prior/after ideal time

Collection at incorrect stage of development

E.g. coriander – fully ripe fruits (should be nearly ripe), clove (flowers are in bud)

Collection of parts which are not medicinally valuable e.g. Chamomile leaves

Collection of incorrect herb (close resemblance to indended herb)

Imperfect preparation (not removing undesired parts e.g. cork from ginger rhizome/incorrect drying conditions)

Incorrect storage: E.g. volatile oils: cool, dry place in air tight containers

Herb Spoilage

When the quality or medicinal

value/usefulness of herb is impaired or

destroyed

Bacterial/fungal action, insects, rodents

Normally results from incorrect storage

(effects of water/temperature)

Any herb which has been contaminated for

bacterial/fungal growth should be rejected

Deterioration

Value or quality of the herb has been impaired

Extraction/Destruction of medicinal actives

Occurs commonly when the herb is expensive, limited

or needed for numerous purposes

E.g. Ginger: removal of medicinally active

constituents in making ginger beer (cooking

purposes)

Aging

Heat

e.g. Volatile oils

Moisture

Light oxidation (promotes the destruction of

VitA)

Admixture

When herbs of another species are added

to the medicinally valuable herb

May be intentional

OR

Result of collection due to unskilled labour

Presence of plant parts other than those

allowed by the definition E.g. excessive stalk

Collection of foreign material (stones, dirt)

NOTE: Certain herbs may be legally mixed with

inert or other materials.

Sophistication

Addition of inferior material with the

intention to decrease medicinal action of

herbs.

E.g. Candle wax coloured yellow and

being offered as Beeswax.

E.g. Addition of flour to powdered ginger

with chillies for potency.

Substitution

Adding an allied drug, or one which is

botanically different.

E.g. Digitalis thaspi for Digitalis purpurea

Evaluation of Crude Drugs

Various methods using QUANTATIVE

MICROSCOPY.

Some of these techniques include

Vein-islet numbers

Palisade ratio

Stomatal number & index

Ash values

EVALUATION OF CRUDE DRUGS

SELF-STUDY!

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