1.pdf An introduction to medicinal plants

An introduction to medicinal plants and its components

1. Medicinal plants
Medicinal plants constitute an effective source of both
traditional and modern medicines
Herbal medicine has been shown to have genuine utility
About 80% of rural population depends on it as primary
health care. [WHO, (2005)]

2. Medicinal plants are the richest bio-resource
drugs of traditional systems of medicine
modern medicines
nutraceuticals
food supplements
folk medicines
pharmaceutical intermediates
chemical entities for synthetic drugs

3. Natural bioactive compounds found in different parts of plant
(fruit, flower, stem, leaf, root)
Provide definite physiological action on the human body
Bioactive substances include tannins, alkaloids, carbohydrates,
terpenoids, steroids and flavonoids
Widely used in the human therapy, veterinary, agriculture,
scientific research and countless other areas
Have inhibitory effects on all types of microorganisms in vitro
Phytochemicals

4. Extraction
……… is the separation of medicinally active portions of
plant tissues using selective solvents through standard procedures
The basic parameters influencing the quality of an extract
•Plant part used as starting material
•Solvent used for extraction
•Extraction procedure

5. Choice of solvents
Successful determination of biologically active
compounds depends on the type of solvent used in the
extraction procedure
Property of a good solvent in plant extraction
•Low toxicity
•Ease of evaporation at low heat
•Promotion of rapid physiologic absorption of the extract
•Preservative action

6. The factors affecting the choice of solvent
•Quantity of phytochemicals to be extracted
•Rate of extraction
•Diversity of different inhibitory compounds extracted
•Ease of subsequent handling of the extracts
•Toxicity of the solvent in the bioassay process
•Potential health hazard of the extractants

7. Solvents used for active component extraction
Water Ethanol Methanol ChloroformEther Acetone
Anthocyanins
Starches
Tannins
Saponins
Terpenoids
Polypeptides
Lectins
Tannins
Polyphenols
Polyacetylenes
Flavonols
Terpenoids
Sterols
Alkaloids
Anthocyanins
Terpenoids
Saponins
Tannins
Xanthoxyllines
Totarol
Quassinoids
Lactones
Flavones
Phenones
Polyphenols
Terpenoids
Flavonoids
Alkaloids
Terpenoids
Coumarins
Fatty acids
Phenol
Flavonols

8. General techniques of medicinal plant extraction
Plant tissue homogenization
Maceration
Infusion
Percolation
Digestion
Decoction
Soxhlet extraction (Hot continuous extraction)
Sonication (Ultrasound extraction)

9. Plant tissue homogenization

10. Maceration"d tn3nM iotl n AtotAnMohAtnAohsnaniMtAnacnin totAn
M ciactonadndtn tc
Whole / coarsely powdered crude drug is placed in a stoppered
container with the solventy n nicAn4no rntrtoihotn onintoa An nintin5nAil nadn
ot1htcnisaia cnhcandtn hPtnritonstnAa tA
Allow to stand @ room temperature for a period of at least 3 days with
frequent agitation until the soluble matter gets dissolved6dtnra.hotndtcnanoiactA$ndtnrioMn%dtnAirn aAnritoai'nan
ottA
The mixture then is strained, the marc (the damp solid material) is
pressed6dtnM rPactAna1haAniotnMioaatAnPl naoia cn on
AtMicia cnitonicAacs
The combined liquids are clarified by filtration or
decantation after standing

11. Infusion

12. Digestion
•A form of maceration in which gentle heat is used
during the process of extraction
•Used when moderately elevated temperature is not
objectionable
•The solvent efficiency of the menstruum is thereby
increased
Microwave digestion system

13. Decoction
Suitable for extracting  water-soluble, heat-stable constituents
Typically used in preparation of Ayurvedic extracts

14. Percolation
•Used most frequently to extract active ingredients in the
preparation of fluid extracts
•The solid ingredients are moistened with an appropriate amount
of the specified menstruum
•Allowed to stand for approximately 4 hours in a well closed
container, After stand time, the mass is packed & the top of the
percolator is closed
•The mixture is allowed to macerate in the closed
percolator for 24 h

15. ,
•Additional menstruum is added as required, until the
percolate measures about three-quarters of the required
volume of the finished product
•The marc is then pressed and the expressed liquid is
added to the percolate
•Sufficient menstruum is added to produce the required
volume
•The mixed liquid is clarified by filtration or by standing
followed by decanting

16. Soxhlet Extraction
(Hot Continuous Extraction)

18. Sonication
(Ultrasound Extraction)
•Involves the use of ultrasound with frequencies ranging from
20 kHz to 2000 kHz
•Increases the permeability of cell walls & produces cavitation
Disadvantage
Deleterious effect of ultrasound energy
(>20 kHz) on the active constituents of
medicinal plants through formation of free
radicals and consequently undesirable changes
in the drug molecules

19. Effect of extracted plant phytochemicals depends on
•The nature & origin of the plant material
•Degree of processing
•Moisture content
•Particle size

20. Variation in extraction methods
•Length of the extraction period
•Solvent used
•pH of the solvent
•Temperature
•Particle size of the plant tissues
•Solvent-to-sample ratio