Herbs as raw material
Content
•
Source of herbs
•
Identification and authentication of herbs
Objective
At the
end of this lecture, student will be able to
•
Discuss the source of herbs, selection, identification
and authentication of herbal materials
Herb:
Ø The
word herb derived from the latin word herba – Grass/green stalks
Ø Herbs
include any part of the plant like leaves, roots, stem, bark etc posses
therapeutic activity
Herbal medicine:
Ø Branch of science deals with medicinal
plants, it includes modern standards of testing of herbs and medicines derived
from natural sources
Herbal Medicinal product: Defined as any medicinal product, exclusively
containing one or more active ingradients of herbal origin
Herbal Drug Preparations
Ø Preparations which are made from herbal
drugs and are prepared by the help of different processes like infusion,
decoction, maceration, distillation, fermentation etc. These include whole
plant/parts, powdered herbal drugs, extracts, essential oil, processed exudates
of herbal materials
Source of herbs:
Ø Plants
have ability to synthesize wide variety of chemical compounds that are used to
perform important biological functions and to defend against attack from
insects, fungi and herbivorous
Ø Many of these phytochemicals have beneficial effects on long term health
when consumed by humans and can be used to treat diseases effectively
Ø Phytochemicals are divided into Primary
metabolites and secondary metabolites
Ø Primary
metabolites – Cabohydrates, proteins and lipids found in all the plants
Ø Secondary
Metabolites: Compounds which have
therapeutic actions, do not have any role in the growth of plants
Eg: Alkaloids, glycosides, tannins, resins, volatile oil,
latex etc
Quinine – Anti malarial
Reserpine – Anti hypertensive
Digitoxin – Cardiac stimulant
Identification and authentication of herbal materials:
Ø Herbal
materials may vary in composition and properties unlike conventional
pharmaceutical products, which are generally prepared from synthetic,
chemically pure compounds by means of reproducible manufacturing techniques
Ø Correct identification and quality assurance
of the starting material is essential for safety and efficacy of the drug
Ø Drugs of poor quality destroys the clinical
efficacy
Ø Taxonomic
method
Ø Herbarium sample
Ø Macroscopic method
Ø Microscopic
method
Ø Physico chemical method
Ø Spectroscopic method
Ø Chromatographic method
Taxonomic method:
Ø Involves
classical botanical methodologies for collection and documentation of the
plant at its source
Ø Botanical origin of the drug is identified and
its scientific binomial, that is genus, species is determined based on this
method
Ø Information
such as vernacular names, site of collection, detail of collector, season of
collection, part collected etc are essential fundamentals even before
authentacation
Herbarium coupon sample:
Ø Sample
of collected material should be kept as a coupon sample in a herbarium or in a
research institute for future reference
Ø Specimens collected from field were dried
using blotting paper and uniform pressure was exerted on blotting papers by
placing them in a plant press
Ø Blotting
paper was changed every day (15 days), so that moisture from the specimen is
removed completely
Ø After
demoisturing, specimens were treated with a solution of HgCl2 in
formalin for about 2 min. They were again dried in dryers and mounted on
herbarium sheet using fevicol
Morphological method:
• Refers to shape, size, colour, odour, taste
and special features like texture and fracture
Shape: Nuxvomica – disc
Aconite – conical
Colour: Fennel – greenish yellow
Senna- greenish
Odour: Umbelliferous fruits – aromatic
Asafoetida – alliaceous
Taste: Licorice – Sweet
Kalmegh – Bitter
Fracture: Kurchi – granular
Picrorrhiza- tough
Microscopical
method:
Ø
To identify
unorganized drug by their known histological characters
Ø
Microscope,
by virtue of its property to magnify, permits the minute structure under study to be
enlarged
Ø
Stains can be
used to distinguish cellular structure
– Phloroglucinol and
con HCl – Lignin (Pink)
– Ruthenium red –
mucilage (Pink)
Histological studies – thin section of drugs
Ø
Cell wall,
cell contents, stomata, trichomes, fibres, vessels etc
Eg: Senna – Paracytic stomata
Vasaka – Diacytic
stomata
Nuxvomica – lignified unicellular
trichomes
Senna – Warty
unicellular trichomes
Datura –
multicellular unbranched trichome
Vasaka –
unicellular glandular trichome
Ø Microscopic linear measurements and
quantitative microscopy
Stomatal number: Average number of
stomata per sq mm of epidermis of the leaf
Stomatal index : Percentage which
the number of stomata form to the total number of epidermal cells; each stoma
being counted as one cell
S.I =
S/E+S S.I =
Stomatal index
S = No of stomata
E
= No of epidermal cells in the same unit area
Palisade
ratio : Average number of palisade cells beneath each epidermal
cells
Vein-islet
number : The number of vein islets per sq mm of the leaf
surface midway between the midrib and margin
Physico
chemical method:
– Moisture content
– Viscocity
– Melting point
– Solubility
– Optical rotation
–
Refractive index
– Ash content
– Extractive value
– Volatile oil content
Spectroscopic
method:
Ø Infrared spectroscopy
Ø Electron spectroscopy for chemical analysis
Ø Atomic absorption Spectroscopy
Ø X Ray diffraction analysis
Ø X-Ray fluorescence analysis
Chromatographic
method:
Ø TLC
Ø HPLC
Ø HPTLC
Ø Gas Chromatography