Methods to Ensure Microbiological Safety of Organically Produced Medicinal Plants: A Review

The production, handling, processing and marketing of over-the-counter medicinal products manufactured from plants is virtually unregulated. This can include dietary supplements, functional foods and nutraceuticals, any of which may contain botanical constituents. Of particular concern is the possible presence of human pathogens in products offered at retail. A review of literature is presented. Options for sterilizing herbal medicinal products, including fumigation, irradiation and heat treatments, are presented. Experiences of the spice industry are discussed as they relate to the development of similar protocols for herbal medicines. Methods used to ensure microbiological safety must be evaluated for their effect on the medicinally active constituents in the plant material. Very little data of this nature are available. Avenues for future research are proposed. Shultz-Bip., Asteraceae] that could serve as a starting point for monograph development (Rushing et al., 2003). Canadian authorities also have published microbiological guidance for foods (Harwig et al., 1998) that are relevant to botanical medicinal products. Spices and medicinal plant products often are investigated in parallel studies due to the similarities in production and postharvest practices. An example of this is found in the reporting of pesticide residues found in spices and medicinal plant products (Abou-Arab and Abou Donia, 2001). Microbiological quality and safety of spices has been the focus of a number of surveys including those of retail markets in the U.S. (Schwab et al., 1982), in India (Banerjee and Sarker, 2003), and in heavily spiced ethnic foods (Candlish et al., 2001). Enumeration of microorganisms in spices and spice mixtures has been an important activity in this industry for decades (Krishnaswamy, 1971), with periodic updates that recognize the risk of fecal contaminants (Satchell, 1989). A relatively recent review of this body of literature is available (McKee, 1995). Clearly the spice industry recognizes that food safety hazards exist in spices. The need to defi ne acceptable microbial limits for herbs is acknowledged but such limits are not clearly defi ned (EMEA, 2001). Imported medicinal herbs have been found, in some cases, to contain microbial contamination. In a survey of St. John’s wort [Hypericum perforatum (L.) Hypericaceae] imported from China, U.S. Pharmacopeia (USP) observed that, before irradiation treatment, a number of samples tested contained E. coli 0157, likely caused by the use of animal manures or human waste (night soil) during production (unpublished, personal communication with USP). Irradiation would eliminate this hazard and this emphasizes the need to include a disinfection step in the processing of medicinal plant products. There is an understandable reluctance in the scientifi c community to publish such results without exhaustive confi rmation because of the impact it might have on the industry in addition to possible liability issues. GMP to help ensure product safety is a key prerequisite for standardization during production, harvesting, processing and marketing. Experiences from the food industry are highly relevant to the herbal medicinal product industry. Food safety concerns led to the development of Hazard Analysis Critical Control Point (HACCP) programs, which have the purpose of ensuring food safety by focusing on all steps from harvest until consumption (USDA, 1998). The basis of HAACP is to identify hazards, defi ned as physical, chemical or microbiological in nature, and to impose controls upon critical steps to reduce risk to consumers. HACCP has served as a useful model for development of GAP and GMP, which go a step further to include all agricultural operations in addition to manufacturing. In the food industry, the cases of fresh fruits, vegetables and spices are most relevant to the botanical medicinal industry. US-FDA (1998) published guidelines for reduction of microbial risks in fresh produce. This was treated more comprehensively by the Joint Institute for Food Safety and Applied Nutrition in a GAP-GMP training manual (JIFSAN, 2002). An invaluable collection of resource materials for fresh produce is available from Cornell University (Bihn et al., 2004) and similar, but less comprehensive, documentation is available from the U.S. spice industry trade association (ASTA, 2003). Many of the guidelines and recommendations in these publications are directly applicable to herbal medicines. Guidelines that specifi cally address botanicals are under discussion at U.S. Pharmocopeia (2003) and some published materials are available from international organizations (EMEA, 2002; WHO, 2003). In all of these resources, specific disinfection protocols are not discussed in a practical manner. No focused attempt has been made to regulate the botanicals industry other than the publication of the Dietary Supplement Health and Education Act (US-FDA, 1994). Monographs for GAP and GMP for specifi c crops are needed. A limited amount of work has been published for feverfew [Tanacetum parthenium (L.) To whom reprint requests should be addressed; e-mail [email protected]. Safety of herbal medicines has been a concern since the commercialization of these products began decades ago (Farnsworth, 1993). Safety is best assured through the implementation of Good Agricultural Practices (GAP) and Good Manufacturing Practices (GMP), the concepts of which intuitively are clear. However to defi ne their meaning in the context of the safety and quality of herbal medicinal products is relatively complex. Key points were reviewed by Franz (1989) and Demarco et al. (1999) expanded the discussion relative to organic production. Increases in consumption of botanicals during the past two decades are forcing a transition from harvesting plants from their native habitat (wild-crafting) to large scale cultivation (Pank, 1993) and have called greater attention to GAP and GMP. Organic cultivation in particular calls attention to microbial safety. Franz (2004) continues to commit signifi cant effort to GAP and phytomedicine quality. US-FDA (2003) also has increased its effort to ensure safety of herbal products through a proposed ruling for GMP for dietary supplements, which presently includes herbal medicinal products. Early attention to herbal product safety focused on chemical residues. One approach was to establish safety coeffi cients for chemical use based on the rate of decay of the applied products (Debska and Lutomski, 1980), a notion that has been rejected in recognition of the fact that many chemicals persist in soils for extended periods and the potential exists for their uptake into plants (Grun et al., 1993). Today we recognize that the safety and health properties of plant-based functional foods, medicines and nutraceuticals are far more complex than previously thought, encompassing issues of microbiological safety, allergens, dosage requirements, toxicity and product standardization. The need for standardization of botanical medicinal products is particularly compelling (Craker, 1999; Cranz, 1999; Phillipson, 1993). Implementation of GAP and AprilBook.indb 292 2/13/06 2:47:09 PM 293 HORTSCIENCE VOL. 41(2) APRIL 2006 Discussions with cottage-scale producers and vendors of herbs and with herbal medicine practitioners have revealed concerns for consumer safety. Methods for disinfecting small lots of fresh herbal products are needed. Some small-scale growers use un-composted organic fertilizers to produce herbs that are delivered to retail markets in a freshly harvested state without sanitizing treatment. The risk of developing illness may exist for consumers that use these products without implementing a kill step, such as in the preparation of teas with boiling water (personal communications with conference attendees; see Rushing et al., 2003). It is useful to review the options available for sanitizing treatments of medicinal plant materials, recognizing that many potential treatments described herein are not certifi ed organic.