Quality control methods for

18. Determination of microorganisms 
Medicinal plant materials normally carry a great number of bacteria and 
moulds, often originating in soil. While a large range of bacteria and fungi form 
the naturally occurring microflora of herbs, aerobic spore-forming bacteria 
frequently predominate. Current practices of harvesting, handling and 
production may cause additional contamination and microbial growth. The 
determination of Escherichia coli and moulds may indicate the quality of 
production and harvesting practices. 
Methods for decontamination are restricted. For example, the use of ethylene 
oxide has been forbidden within countries of the European Union. Treatment 
with ionizing irradiation is also forbidden or requires a special registration 
procedure in some countries. 
In addition, the presence of aflatoxins in plant material can be hazardous to 
health if absorbed even in very small amounts. They should therefore be 
determined after using a suitable clean-up procedure. 
Test for specific microorganisms 
The conditions of the test for microbial contamination are designed to minimize 
accidental contamination of the material being examined; the precautions taken 
must not adversely affect any microorganisms that could be revealed. 
Recommended procedure 
Pretreatment of the material being examined 
Depending on the nature of the crude medicinal plant material, grind, dissolve, 
dilute, suspend or emulsify the material being examined using a suitable 
method and eliminate any antimicrobial properties by dilution, neutralization or 
filtration. 
Water-soluble materials 
Dissolve or dilute 10 g or 10 ml of plant material, unless otherwise specified in 
the test procedure for the material concerned, in lactose broth or another suitable 
medium proven to have no antimicrobial activity under the conditions of the 
test, adjust the volume to 100ml with the same medium. (Some materials may 
require the use of a larger volume.) If necessary, adjust the pH of the suspension 
to about 7. 
Non-fatty materials insoluble in water 
Suspend 10g or 10ml of material, unless otherwise specified in the test procedure 
for the material concerned, in lactose broth or another suitable medium proven 
to have no antimicrobial activity under the conditions of the test; dilute to 100ml 
with the same medium. (Some materials may require the use of a larger 
volume.) If necessary, divide the material being examined and homogenize the 
suspension mechanically. A suitable surfactant, such as a solution of polysorbate 

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Quality control methods for medicinal plant materials 
80 R containing 1 mg per ml may be added. If necessary, adjust the pH of the 
suspension to about 7. 
Fatty materials 
Homogenize 10g or 10ml of material, unless otherwise specified in the test 
procedure for the material concerned, with 5g of polysorbate 20R or polysorbate 
80R. If necessary, heat to not more than 40°C. (Occasionally, it may be necessary 
to heat to a temperature of up to 45°C, for the shortest possible time.) Mix 
carefully while maintaining the temperature in a water-bath or oven. Add 85 ml 
of lactose broth or another suitable medium proven to have no antimicrobial 
activity in the conditions of the test, heated to not more than 40°C if necessary. 
Maintain this temperature for the shortest time necessary until an emulsion is 
formed and, in any case, for not more than 30 minutes. If necessary, adjust the 
pH of the emulsion to about 7.