The document discusses various methods for extracting components from medicinal plants. It describes maceration, where fragmented plant material soaks in solvent over 2-14 days. Digestion is similar but involves slight heating. Infusion and decoction extract using hot or boiling water. Distillation extracts volatile oils. Supercritical fluid extraction uses pressurized carbon dioxide as a solvent. Continuous extraction methods like Soxhlet extraction involve repeatedly treating plant material with fresh solvent to efficiently extract components. The key factors that influence extraction method selection include the plant composition, solvent characteristics, and temperature effects on solubility and stability of chemical components.

1. PHARMACOGNOSY
Lecture 1d

2. Drug evaluation
• Phytochemical investigation.
• Phytochemistry. Extraction methods.
Suggested bibliography:
Pharmacognosy, Kokate, Purohit & Gokhale, 2004, Chap. 6. pp. 99-105.
Pharmacognosy, Trease and Evans, 1996, Chap..
Textbook of Pharmacocognosy, Handa & Kapoor, 2003, Chp 24, 10, 15.

3. OBJETIVES.
The student must know how
obtain the components present in
medicinal plants through the
stablished extraction methods.

4. Phytochemistry. Extraction methods.
Phytochemistry implies the chemical examination of the
active fraction after its extraction.
The systematic investigations of plant material for
its phytochemical behavior involve different
stages. One of them is the extraction of chemical
constituents.

5. Factors influencing the different methods
of extraction
The methods and techniques for extraction and isolation of
active principles from crude drugs, depend on several
factors as the following:
a) Establish the right procedure and solvent selection
taking on account the chemical composition of the
raw material standardized.
b) Fragmentation (particle size).
Leaf, flower and herbaceous plants 5mm
Bark, stem and roots 3mm
Seed and fruits 0,5 mm

6. g) Viscosity of the médium, solvent characteristics.
h) Fluctuation in the concentration among the raw
material (higher) and the solvent of the
extraction (lower).
i) Ph of the extraction médium.
j) Influence of temperature on the solubility
and decomposition of the chemicals.
k) Product stability on experimental
conditions.

7. In the pharmaceutical market there are
usually found four types of extracts:
Are the must common and contain the whole
diversity of chemical components. The two
common different kinds of extracts are:
Fluid extract: concentration of the drug extract
until 1 ml contain the extractives of 1 g of plant.
Tincture: Concentration of the drug extract to
certain percentage. For example:
10% tincture  1 g drug / 10 mL
20%  1 g drug / 5 mL
Hydro alcoholic extracts

8. Dry extracts
Are obtained concentrating the liquid
extraction through vacuum evaporation or
spray dry system until a powder is obtained.
As termolabile substances could change its
chemical structure, spray dry is used
nowadays. This procedure preserves the
enzymatic, vitamin and hormonal content of
fresh plant preparations.

9. Soft extracts
Are thick liquids or semisolid masses
that are obtained evaporating the
extraction solvent without reaching to
dryness. In general, each gram of the
soft extract is equivalent to 4-6 g from
each 100g of the raw material.

10. Oily extracts
When the substance of interest is
hydrophobic and the evaporation of
the extract finally is oily in its
consistence

11. The main techniques for extraction are:
Maceration
Lixiviation or percolation
Digestion
Soxhlet or continous extraction
Distillation for volatile components
Infusion
Decoction
Cold extraction
Supercritical fluid extraction
Continuous extraction

12. Maceration: The word maceration means softening. It is a cold
extraction employed in the production of a number of
preparations such as tinctures, extracts and concentrated
infusions. The fragmented crude drug is left to soak in the solvent,
so the cellular substances dissolve in it.
The material is agitated periodically during 2-14 days in a
hermetically closed flask. Then, the solvent is filtrated pressing the
residue, and washing it with a small volume of the solvent.
Digestion: It is another kind of maceration where the
powdered material is slightly heated to increase the
extracting power. So as the solvent can be used
continuously by recycling, a condenser can be adjusted
to the flask where the digestion is being carried out.

13. Cold extraction or maceration modification (in a large flask
with agitation using a stirrer) in which the ground dried
material is extracted at room temperature sequentially
with solvents of increasing polarity: hexane (or petroleum
ether), then chloroform, ethyl acetate, acetone, methanol
and finally water. The major advantage of this protocol is
that it is a soft extraction method, the extract is not heated
and there is therefore, little potential degradation of
natural products according to their solubility (and polarity)
in the extraction solvents.

14. Lixiviation: The powder material is firstly
macerated for 30 min, and the placed in the
percolator, making the solvent to flow through
it until the air bubbles disappear.
Hot percolation, the biomass is added to a round-bottomed
flask containing solvent and the mixture is heated under
reflux. Typically, the plant material is stewed using solvents
such as ethanol or aqueous ethanol mixtures.
The technique is sometimes referred to as total extraction
and has the advantage that, with ethanol, the major
hydrophobic and hydrophilic compounds are extracted.

15. Infusion: The drug is extracted with hot water, but
not boiling, or with cold water. The water is purred
over the crude drug, keeping the container well
closed during about 15 min.
Decoction: The crude drug is boiled in water during
15-30 minutes and filtered out in boiling solvent.
For the most usual drugs the proportion is each 1 g of
drug per 30 ml of water.
For drugs that contain toxic substances the proportion
is each 1 g of drug per 400 ml of water.

16. Distillation: is the process of
evaporating a substance,
condensing the vapors and getting
them as liquid. This method
comprises several variants that
depend on the drug nature and the
chemical transformation of the
substances under heat.
The equipment in the graph
produce vapor to distill volatile
oils.

17. Supercritical fluid extraction utilizes the fact that some
gases behave as liquids when under pressure they show
solvating properties. The most important example is
carbon dioxide which can be used to extract biomass and
has the advantage that, once the pressure has been
removed, the gas boils off leaving a clean extract. Carbon
dioxide is a non-polar solvent but the polarity of the
supercritical fluid extraction solvent may be increased by
addition of a modifying agent, which is usually another
solvent (e.g. methanol or dichloromethane).

18. Continuous extraction: The plant material
is treated with solvents of increasing
polarity that dissolve one or some of its
components. This methods require
specially designed equipments such as the
Soxhlet apparatus and the liquid-liquid
extractor.
The biomass is placed on a Soxhlet
thimble constructed of filter paper,
through which solvent is continuously
refluxed.

19. Soxhlet apparatus

20. The Soxhlet apparatus will empty its contents
into the round-bottomed flask once the
solvent reaches a certain level, as fresh
solvent enters the apparatus by a reflux
condenser.
Extraction is very efficient and compounds
are effectively drawn into the solvent from
the biomass due to their low initial
concentration in the solvent.
A, powdered drug for extraction in thimble
and plugged with a suitable fibre, e.g.
defatted tow or cotton wool.
Solvent refluxes into thimble and siphons
into flask B containing boiling solvent,
when receiver is full.

21. The method suffers ,from the same drawbacks ,as other hot extraction methods (possible
degradation of products), but it is the best extraction method for the recovery of big yields of
extract.
Three stage of continuous extraction and solvent recovery:
left, extraction by boiling with solvent; center, percolation stage;
right, removal of solvent.
A, sample for extraction;
A1, exhausted drug;
B, solvents;
B1 recovered solvent;
C, solvent containing
soluble plant
constituents;
D, final extract.

22. Concluding remarks
• Summarize the main stages for
phytochemical studies.
• Mention the main methods of
extraction.