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28 Textbook of Pharmacognosy and Phytochemistry I
3
Quality Control of
Drugs of Natural Origin
INTRODUCTION
As per WHO estimate about 80% population
of developing countries relies on traditional
medicines, mostly of plant origin for their
primary healthcare needs. The widespread
popularity towards the traditional medicine
in Asia, Europe and USA has induced high
growth and development worldwide. Hence
quality specification of crude drugs in
demands are being taken up by number of
pharmacopoeias (British Pharmacopoeia, the
European Pharmacopoeia the United States
Pharmacopoeia, Indian Pharmacopoeia), the
National formulary and other national
publications. The quality specifications are
usually characterised in monograph of crude
drugs. A monograph usually comprises of:
• Name with biological and geographical
source of origin of crude drug
• Morphological characters
• Identity comprising macro- and micro-
scopic characters and chemical tests for the
active components
– Purity test
– Quantitative determination
– Biological evaluations
– Storage conditions.
ADULTERATION OF DRUGS OF NATURAL ORIGIN
Adulteration in broad and legal sense is an
addition of another substance, plant part or
plant product to increase the bulk of material
with the result, loss in quality of the raw
material.
Types of adulteration:
1. Intentional
2. Accidental/un-intentional
Intentional adulteration: Deliberate admixture
of inferior, spoiled, deteriorated drug and
substitution with the intention to increase the
profit margin.
Unintentional or accidental adulteration: It
is usually attributed to ignorance, carelessness,
engagement of unskilled labour, and by lack
of storage facilities.
Intentional Adulteration
Addition of undesirable part of the drug, e.g.
in male fern (roots and dead portions are
included into the Rhizome and leaf bases)
Tamarind (outer part of the pericarp of the
fruits are not properly removed and preserved
in sugar); Ginger (cork not-removed from the
Rhizome); Quillaia (Rhytidome are also
included with inner part of the bark.
Inferiority: Admixture the raw material having
low concentration of chemical constituents, e.g.
Mixing the wildly cultivated drug with the
cultivated one because of the morphological
resemblance with authentic drug.
The inferior drugs may or may not have the
therapeutic component, e.g. different species
of senna leaflets, Arabian senna, (Cassia
angustifolia); dog senna (Cassia obovata) and
ranawara (Tamil) Cassia auriculata.
Glycyrrhiza glabra L. roots are being mixed
with Glycyrrhiza glandulifera stolon and roots.
Japanese ginger (Zingiber mioga Roscoe) and
28
Quality Control of Drugs of Natural Origin 29
Martinique ginger (Z. zerumbet Rose) with
Zingiber officinale (medicinal ginger).
Powdered ginger is adulterated with rice
powder, wheat flour and with ginger waste.
Adulteration (sophistication): Cheaper
natural drug with genuine drugs.
It is deliberate mixing of inferior material
with the genuine to increase the bulk, e.g.
asafoetida (Ferula asafoetida) is adulterated with
Gum arabic or wheat flour. Chirata (Swertia
chirata with Swertia paniculata).
Substitution with a factitious material:
Addition or replacement of the genuine drug
with factitious mixture of similar composition,
e.g. Lemon oil-replaced with citral (from the
oil other than lemon oil) and terpene removed
from the oil of lemon. Nutmeg-broken kernel,
moulded with clay and shaped pieces of wood.
Substitution with entirely different drug:
Supplying the drug with similar morphological
characters but different chemically, e.g. palm
oil with olive oil. Belladonna leaves are
substituted with Solanum nigrum leaves.
Substitution with artificially manufactured
substitute: Invert sugar having similar colour
and taste with natural honey and the beeswax
is substituted with yellow coloured paraffin wax.
Accidental spoilage: Crude drug stored at
unhygienic house may gets spoiled by microbial,
fungal or bacterial growth; with the result
loss in therapeutic efficacy of the drug. Drug
may get toxic to human being because of
phytotoxin growth on the drug.
Adulteration by admixture of foreign materials:
Sometime to increase the bulk of the drug
materials; sand, stone pellets are mixed with
resinous drug, gum acacia, gum tragacanth
and lime stone in asafoetida, coal tar in opium.
Addition of synthetic material: Addition of
citral to lemon oil; benzyl benzoate to balsam
of Peru.
Many drugs are processed on large scale
for the isolation of active principles and
subsequently exhausted material are substituted
for genuine drugs, e.g. clove, umbelliferous
fruits and cardamom (volatile oils removed);
Indian Hemp and Jalap (resins removed);
ginger (volatile oils and resins removed);
Balsam of tolu (balsamic acid removed) and
liquorice (glycyrrhizin and other water soluble
matter removed), etc.
Addition of vegetative part of the plant:
Addition of stem part into senna leaflet, buchu
and digitalis leaves, blown up clove flower to
clove bud.
Deterioration of Herbal Drugs
Crude drugs are prone to deterioration while
stored in store house because of light,
temperature, and humidity produce detrimental
effects on the active principle of the drugs with
the result loss in therapeutic potential. Above
that the drugs may also get attacked by insects
to eat out the nutrients.
Factors Affecting the Deterioration
Light: Photosensitive drugs are affected by
light—should be kept away from light or the
containers should be resistant to sunlight
as amber coloured glass containers or the
containers be wrapped in light resistant paper.
The following is the list of drug which can be
affected by light:
Worm seeds which on exposure to sunlight
darkens and eventually becomes dark.
Santonin and Rhubarb powder. Its yellow
colour gets deteriorated in sunlight and it
changes to red colour.
Moisture or humidity: Drugs containing
cardiac glycosides gets hydrolysed in the
presence of moisture and temperature, e.g.
Digitalis leaves and Scilla scale leaves, it also
contains hygroscopic mucilage which become
sticky.
Temperature: When drugs exposed to high
temperature and moisture the enzyme present
in cell, gets coagulated and becomes inactive
to protect the secondary notabilities, e.g.
volatile oils containing, drugs, e.g. Labiatae
family, rose petals and chamomile.
Adsorbent—Cotton fibre becomes nonabsorbent on storing at high temperature
which is because of fat contents which gets
spread over the surface of fibre, thus make it
non-absorbent.
30 Textbook of Pharmacognosy and Phytochemistry I
Oxygen: Air also effects the crude drugs as it
causes oxidation of the drugs, e.g. volatile oils.
The oxidation process alters the odour of
the oil, viscosity and its therapeutic potency.
The main constituents of the essential oil on
combining with atmospheric oxygen causes
negative chemical change (oxide and peroxide
are often formed), e.g. limonene-2-hydroxide
formed from limonene, which is slightly toxic.
Rancidification of the fixed oil due to peroxidation
thus, loss in vitamin, e.g. cod liver oil.
Mould attack: The crude drugs are also being
attacked with same type of mould as those are
found in food product, the commonly found
moulds are species of Rhizopus, Mucor,
Penicillium and Eurotium. Their presence
identified by their characteristic smell because
of oxidation. Conversion of alcohol to aldehyde
or ketone and aldehyde to carboxylic acid.
Esterification: Glycosylation, acetylation,
condensation, etc. with the result new chemical
changes take place which otherwise not
present in the normal components of the
drugs.
Insects and other pest attack: Most of the
drugs, even stored well are liable to attack by
insect pests (especially beetles), who remained
hidden in the drug but at the certain stage
(larvae) of development they appear on the
surface of the stored drug through small
circular holes and fine powdered material
appear at the bottom of container. The drugs
which are commonly infested are ginger,
belladonna leaves and roots, nutmeg, coriander,
stramonium and dandelion.
The insects eat both carbohydrates and
protein components of the drug.
Following are the most commonly reported
insect found in drugs: Stegobium paniceum
(Drug-room beetle or Biscuit weevil) Ptinus fur
and Ptinus tectus, Lasioderma serricorne (cigar-
beetle), Lyctus brunneus (powder-post beetle),
Niptus hololeucus (The Golden spider beetle)
Calandra granaria and Calandra oryzae (Grain
weevils).
In addition to the beetles mentioned above
Mites may also attack drugs like Ergot,
Cantharides and crushed linseed by tearing up
tissues with their mandibles. Commonly
founded mites are Tyroglyphus longior, Aleurobius
farina and Glycyphagus spinipes.
A damp atmosphere is favourable to the
development of fungi and drugs may become
covered with mould. The commonest fungi
found are species of Penicillium (Blue mould),
Eurolium (Green mould) and Mucor. Certain
beetles, e.g. Cryptophagus acutangulus Gyil, feed
exclusively on the fungi developed on the
bales of drugs (liquorice) store in damp
warehouse.
DRUGS EVALUATION
It is the process of analysing the drugs for its
identity, purity, quality and detection of type
of adulterants by comparing the parameter
with the reference sample.
The following are parameters to be checked:
i. Organoleptic properties
ii. Morphological characters
iii. Microscopic characters
iv. Physical
v. Chemicals
vi. Biological evaluations.
ORGANOLEPTIC PROPERTIES (EVALUATION)
Organoleptic: Involving the use of sense
organs as taste, colour, odour and feel of
drugs/substance/food. These characters are
useful, often in a supplementary way in
evaluation of drugs, especially applicable to
drugs containing volatile oils or pungentconstituents, e.g. capsicum and to the detection
of the effect of inadequate drying of drugs.
Colour: The drugs of the aerial part of the
plants—leaves, leaflets, stems and branches
are always green in colour. The intensity of the
colour also indicates the quality of the sample.
Underground part of plant is always nongreen (free from chlorophyll). Flowering part
(petals) always are coloured orange, pink,
violet, etc.
For proper examination, untreated samples
are examined under defused sunlight or
artificial light having same wavelength as that
Quality Control of Drugs of Natural Origin 31
of daylight. Colour parameter helps to
segregate the parts of the plant drugs.
Odour: Odour can be examined by slow and
repeated inhalation. In the case of innocuous
odour even the small portion of the plant
sample is sufficient, e.g. asafoetida.
In case of weak smelling drug, the sample
is lightly crushed either in hand or by applying
light pressure and putting it on boiling water
in watch glass or Petri dish followed by
inhalation.
The odour parameters: These are rancid,
fruity, aromatic, musky and mouldy. The
quality or adulteration can be characterised by
weak, distinct and strong odour.
Rancid odour indicates spoilage of fixed oil
containing drugs.
Taste: Before proceeding to taste of the
unknown sample, one has to be sure about its
non-poisonous properties, otherwise it can be
fatal. This parameter is useful to evaluate the
drugs having characteristic taste, e.g. bitter
(cinchona, chirata, etc.) sweet (honey, stevia).
Sour taste—Tamarindus, Salty—Cassia tora,
Bitter—Andrographis paniculata, Pungent—
Elettaria cardamomum, Astringent—Saraca
ashoka.
Feel or Texture
This parameter is helpful in evaluation of the
surface characters like smooth, rough, hairy
and gritty. This can be achieved by rubbing
the sample between thumb and forefingers.
Bending the sample gives information
regarding the softness or brittleness. Then
check the freshly fractured surface whether it
is fibrours or smooth, rough, granular, etc., e.g.
Centella asiatica smooth surface.
Spongy: Cork oak (Quercus robur)
Soft-silky: Eschscholzia californica (California
poppy), Aegle marmelos (leaves beneath).
Furry plant: Artemisia spp.
Texture is anything with an irregular surface.
This is because of fine hairs, scales, thorns and
lumps or any other protuberance.
Rough stem plant: Spinach and sunflower.
Morphological Evaluation
For morphological evaluation, the crude drugs
are classified into leaves, stem, flowers, fruit
seeds, bark, wood and roots. The adulterant
shows marked difference in morphology from
the authentic material.
Leaves: Leaves are flattened outgrowth of stem.
They are of two types—simple and compound
leaf. Simple leaves have bud in their axil while
no bud in the axil of compound leaves. The whole
leaf is divided into many segments which arise
on a common rachis known as leaflets.
Leaves are of different size, shape, apex,
margin, base and venations; are the
parameters used for the identification/
evaluation of leafy crude drugs.
Shape of lamina: The flat part of the leaf,
which is green in colour, is known as lamina
which always have different shape and
venation, which are characteristic point for
identification (Fig. 3.1).
Shape: The common structure of lamina has
the following description—circular, oblong,
cordate, ovate, obovate, oval, linear and
lanceolate.
Apex of leaf: The outer end of leaf lamina that
is opposite the petiole. It varies from plant to
plant and is useful in identification and
evaluation. Term used to describe the apex are
acute, acuminate, obtuse and tunicate (Fig. 3.2).
Base of leaf: Lower end of leaf lamina which
may be symmetrical, asymmetrical, cordate
and decurrent (Fig. 3.3).
Margin of leaf: Margin of the leaf lamina may
be entire, serrate (sharp edge), dentate, crenate
and sinulate (Fig. 3.4).
Venation: The pattern in arrangement of veins
in the blade or lamina of a leaf is called
venation. There are three types of venation:
Reticulate, pinnate and parallel venation. Most
of the monocot plant leaf shows parallel
venation (Fig. 3.5).
Compound leaf: When attachment of leaf to
stem is examined, it can be determined if leaf
is attached directly to stem, leaf is simple
(pinnate or palmate). In compound leaf it is
paripinnate or imparipinnate (Fig. 3.6).
32 Textbook of Pharmacognosy and Phytochemistry I
Fig. 3.1: Shapes of lamina
Fig. 3.2: Apex
Parallel, Pinnate and Reticulate (Fig. 3.5)
Parallel venations: The secondary veins run
paralled to each other of a central primary
vein, e.g. Banana leaf venation.
Pinnately: Veined leaves have a single
primary vein from which smaller veins
branched off like the division of feather
(Fig. 3.5).
Quality Control of Drugs of Natural Origin 33
Fig. 3.3: Base of leaf
Fig. 3.4: Margin of leaf
Fig. 3.5: Venations
Fig. 3.6: Compound leaf
34 Textbook of Pharmacognosy and Phytochemistry I
Reticulate: Veins are arranged in a net-like
pattern on both sides of the midrib. Dicot
plants.
Description of aerial stem: The stem is an
aerial axis of plant that bears leaves, flowers
and fruits. It conducts water and minerals
from root and food from the site of synthesis
to part of the plant where it is needed.
Herb sample stem can be described in terms
of shape, colour, dimension, upright or
creeping, smooth or ridged, hairs are present
or absent.
Arrangement and Position of
Leaves on Stem
The terminologies used to describe the
arrangement is as follows:
Cauline: Leaves arising from the stem.
Radical: Leaves starting from the crown of the
stem.
Adnation: Part of leaves remain fused with
stem.
Opposite and decussate: It is cauline but arises
in pairs, alternately at right angles to the stem.
Alternate: The leaves arise from stem in
alternate manner (Fig. 3.7).
MORPHOLOGICAL CHARACTERS OF UNDERGROUND ORGANS
Crude drugs from underground organ consist
of root structure and stem structure as storage
organ including true bulbs, corms, tubers,
enlarged hypocotyls and rhizomes. Rhizome
looks to be similar to root but has internal
structure arrangement similar to a stem,
e.g. gentian and rhubarb. These drugs are
commonly classified as root but actually both
of them consist of rhizomes.
Rhizomes have scale leaves with axillary buds
on the surface and have adventitious roots or
Fig. 3.7: Arrangement of leaves on stem
Quality Control of Drugs of Natural Origin 35
scars, whereas roots do not have scale
leaves and buds. They have main tap root
and the lateral root—no nodes/internodes
(Fig. 3.8a).
Underground organs are characterised by the
absence of chlorophyll. They are often swollen,
hence they are cut into small pieces and dried
for storage and transportation.
Underground organs are of following size
and shape—straight, conical, cylindrical,
tortuous and fusiform (Fig. 3.8b).
Morphological Evaluation of Bark
Bark is the outer protective layer of woody
plants, roots and shrubs. It refers to all tissues
outside the vascular cambium.
A young bark is composed of:
1. Epidermis: Closely packed cuticle,
parenchymatous cell with occasional
stomata.
2. Primary cortex: It is usually made up of
chlorophyll-containing collenchyma and
parenchyma tissue.
Endodermis: Innermost of cortex, closely
packed parenchyma often containing starch.
Pericycle: Composed of parenchyma and fibre
tissue. Sometimes pericyclic fibres are in
groups opposite to patches of phloem.
Phloem: Composed of parenchyma, sieve tube
and companion cell separated by radially
arranged medullary rays (Fig. 3.9a).
In old bark secondary growth appears
because of activation of cork cambium or
phellogen with the result primary bark is
tangentially stretched, and outer layer
compressed and torn out or divided by radial
walls and the parenchymatous cells of the
cortex—becomes thickened and converted into
sclerenchymatous cells. Inner side cambium
produces secondary phloem consisting of
alternating zone of sieve elements and phloem
fibres. Pericyle layer also ruptured and even
in few barks it disappears as sclerenchyma.
In the epidermis and primary cotex, cork
cambium or phellogen may arise, which on
outer side produce cork and in inner side
secondary cortex or phelloderm (chlorophyll
containing suberized cell). All these three
layers are known as periderm (Fig. 3.9b).
The primary cortex will lie on the outer side
of cork and will gradually thrown off, the
stomata will be replaced with lenticells for the
gaseous exchange.
The barks are flat when removed freshly but
on drying its curvature increases except in the
case of large pieces of trunk bark, if subjected
to pressure are flat. The terminology used to
(a)
Turmeric rhizome (Fusiform)
(b)
Fig. 3.8a and b: Shape of underground drugs
36 Textbook of Pharmacognosy and Phytochemistry I
(a)
Fig. 3.9: Microscopic structure of bark; (a) young bark; (b) old bark
describe the curvature shown in (Fig. 3.10). These
curvatures are characteristic of official barks.
For pharmacognostical evaluation the bark
may be described under following headings:
i. Origin: Trunk bark or root bark.
ii. Size and nature of curvature: According
to the extent of curvature every bark
develops its specific shape.
Quill, double quill, compound quill,
channelled, recurved and curved (Fig. 3.10a).
Surface Characters
The commercial barks have two surfaces—
outer and inner surface. Depending upon the
surrounding environment epiphytes may
grow on the surface of a plant in forest. Hence,
when trunk barks are removed and prepared,
there is presence of epiphytes like lichens and
moss may appear on the outer surface.
Other than epiphytes on old barks
rhytidome (dead layer of cork cells) is seen
which looks like wrinkles. Some barks are
scraped at the time of preparation to give
smooth surface. Hence, to describe the surface
characters of bark, terms used are:
Outer surface: The presence of lichens,
mosses, lenticells, cracks/furrows, colour
before and after scraping.
(b)
Inner surface: Colour, striations.
Fracture: Outer surface generally have short
but inner surface fracture depends upon the
extent of secondary growth, i.e. fibrous,
splintery or granular.
Transverse surface: Freshly broken (fractured)
bark on staining with phloroglucinol and
hydrochloric acid shows lignified elements
(sclereids and vessels), medullary ray and cork.
Morphological Characters of Wood
Wood is a porous and fibrous structural tissue
of stems and roots of tree. It is of two types,
i.e. hardwoods and softwoods. Hardwood
come from angiosperms and softwood come
from gymnosperms.
Wood made up of secondary tissues
produced by cambium on inner side. These
consist of fibres, vessel elements, tracheids and
parenchyma. All the tissues are generally
lignified but exceptions are there as in case of
wood of belladonna root, non-lignified tissue
are predominant to lignified one. This can be
confirmed by staining the cut surface of the
wood, with phloroglucinol and hydrochloric
acid. Medullary rays: width and height of the
ray are characteristic in wood of quassia and
rhubarb.
Quality Control of Drugs of Natural Origin 37
Fig. 3.10a: Curvature of bark
The wood block has two regions:
1. Heart wood
2. Sap wood.
Heart wood: It is the central region which is
coloured because of the deposit of waste
products such as resins, tannins and colouring
matter in the wood of old tree.
Sap wood: It is the outer wood still retains its
normal appearance and functions. Each year tree
forms new cells arranged in concentric rings
known as annual rings or annual growth rings.
In some tropical species these rings are not well
marked because of the seasonal interruptions
in growth, hence false annual rings are formed.
Annual ring shows amount of wood
produced during one growing season. It
appears as darker ring in transverse section.
These rings are formed due to activity of
extrastelar cambium or intrastelar cambium
or both (Fig. 3.10b).
Wood grains which describe the alignment,
texture and appearance of wood fibres are also
characteristic of plants.
Fig. 3.10b: Internal structure of wood
Grains of wood are indicator of the
arrangement of annual rings and medullary rays.
Wood can be identified under the following
headings:
Size and colour: Colour depends upon the
ration of heart wood and sap wood.