Ensuring Microbiological Quality of Herbal Products

A new USP chapter <1120> Ensuring Microbiological Quality of Articles of Botanical Originis (ABOs) is being proposed by the Joint Subcommittee on Microbiological Issues in Dietary Supplements and Food Ingredients. It provides information on practices to prevent and methods to treat microbiological contamination. The chapter was previously announced as <1114> Ensuring Microbiological Quality of Articles of Botanical Origin.

Good Practices for Preventing Microbial Contamination

Compliance with current Good Manufacturing Practice (CGMP) requires the control and prevention of microbiological contamination of herbal raw materials, processed ingredients, and finished herbal drug products. Raw materials must not contain levels of undesirable microorganisms that would cause the product to be adulterated, or the material must be pasteurized or otherwise treated.

According to chapter <1120>, implementing quality assurance standards such as Good Agricultural and Collection Practice (GACP) and GMP is the best way to minimize or prevent microbial contamination. Prevention of contamination through these measures is preferable to the reliance and use of postharvest decontamination methods. The European Medicines Agency (EMA) Reflection Paper on Microbiological Aspects of Herbal Medicinal Products and Traditional Herbal Medicinal Products emphasizes that a decontamination treatment may not be used as a substitute for GACP or GMP or to disguise poor microbiological quality of a starting material of herbal origin. In the US, GACP compliance is mandatory for herbal drug active ingredients but voluntary for botanical dietary supplement components. The FDA has not established GACPs for botanical drug active ingredients, instead deferring to the World Health Organization (WHO) Guidelines on GACP for Medicinal Plants and the EMA Guideline on GACP for Starting Materials of Herbal Origin, as acceptable guidelines for applicants to implement.

The Health Canada Quality of Natural Health Products Guide also states that Natural Health Product (NHP) license applicants must ensure that GACP and GMP have been implemented through the herbal supply chain to ensure low levels of microbial contamination. "Once a crude botanical raw material leaves the control of a GACP-compliant farm or wild collection operation and enters a component processing or finished product manufacturing facility, suitable GMPs are necessary to avoid new contamination", the USP chapter <1120> states.

Methods for Reduction of Microbial Contamination

Factors that can influence the microbiological quality of herbal starting materials (i.e., the microbial bioburden) include the following:

• The nature of the plant and its natural barriers (e.g., resins or waxy suberin deposits)
• Structure of the plant (e.g., a protective bark or cuticle)
• Plant composition (e.g., naturally occurring antimicrobial compounds such as volatile oils)
• Climate
• Humidity
• Irrigation
• Fertilization
• Method of harvest (e.g., hand harvest or machine harvest)
• Postharvest handling and transport
• Physical state of the herbal material (e.g., whole or cut)
• Technological treatments (e.g., extent of drying and remaining water activity, sorting, cutting, sifting)
• Packaging and storage conditions  

According to the USP, microbial reduction treatment of herbal raw materials is routine in the global herbal ingredient market. The extraction process itself may provide a degree of microbial decontamination. In addition, there are other methods available, like for example ozone treatment, use of ethylene oxide or ionizing radiation. The use of ethylene oxide leads to a considerable reduction of the microbial bioburden. However, treatment of herbal drugs with ethylene oxide is, for example, prohibited in the European Union (EU). Irradiation is considered an additive for which the FDA has set out authorized uses and limitations. Foods that are irradiated should be adequately labeled according to international and national guidelines with statements such as “Treated with radiation” or “Treated by irradiation”. In the EU, irradiation is restricted or not permitted for use on ingredients of registered Herbal Medicinal Products (HMPs) in several member states. Irradiation is, however, permitted in Canada for ingredients of licensed NHPs.

The chapter <1120> has been published for comment in Pharmacopeial Forum PF 51(1). Comments can be submitted until 31 March 2025. The draft is available following registration to the Pharmacopeial Forum.