Review
Assessment of genotoxicity of herbal medicinal products: Application of the “bracketing and matrixing” concept using the example of Valerianae radix (valerian root)
- Under a Creative Commons license
Open Access
Abstract
An
assessment of genotoxicity is a precondition for marketing
authorization respectively registration of herbal medicinal products
(HMPs), as well as for inclusion into the ‘Community list of herbal
substances, preparations and combinations thereof for use in traditional
herbal medicinal products’ established by the European Commission in
accordance with Directive 2001/83/EC as amended, and based on proposals
from the Committee on Herbal Medicinal Products (HMPC).
In
the ‘Guideline on the assessment of genotoxicity of herbal
substances/preparations’ (EMEA/HMPC/107079/2007) HMPC has described a
stepwise approach for genotoxicity testing, according to which the Ames
test is a sufficient base for the assessment of genotoxicity in case of
an unequivocally negative result. For reducing efforts for testing of
individual herbal substances/preparations, HMPC has also developed the
‘guideline on selection of test materials for genotoxicity testing for
traditional herbal medicinal products/herbal medicinal products’
(EMEA/HMPC/67644/2009) with the aim to allow testing of a standard range
of test materials which could be considered representative of the
commonly used preparations from a specific herbal drug according to a
‘bracketing/matrixing’ approach.
The purpose of this
paper is to provide data on the practical application of this
bracketing and matrixing concept using the example of Valerianae radix,
with the intention of facilitating its inclusion in the “Community
list”. Five extraction solvents, representing the extremes of the
polarity range and including also mid-range extraction solvents, were
used, covering the entire spectrum of phytochemical constituents of
Valerianae radix, thereby including polar and non-polar constituents.
Extracts were tested in the Ames test according to all relevant
guidelines. Results were unequivocally negative for all extracts. A
review of the literature showed that this result is in accordance with
the available data, thus demonstrating the lack of a genotoxic
potential.
In conclusion the two guidelines on
genotoxicity provide a practically applicable concept. Valerianae radix
has no genotoxic potential, supporting its use in HMPs and its inclusion
in the Community list.
Graphical abstract
Keywords
- Genotoxicity;
- Herbal medicinal products;
- Valerian root;
- Bracketing and matrixing;
- HMPC;
- Ames-test
Introduction
The frame for the regulation of HMPs in the European Union (EU) is given by directive 2001/83/EC as amended by directive 2004/24/EC. According to regulation (EC) No 726/2004,
the committee for herbal medicinal products (HMPC) is responsible for
preparing the view of the European Medicines Agency (EMA, formerly EMEA)
on herbal medicines (Knöss and Chinou 2012).
According to the guideline EMEA/HMPC/32116/2005, for many herbal
substances and preparations, used in well-established or traditional
herbal medicinal products (HMPs), a safety profile in accordance to
modern standards is supported or at least partially substituted by their
documented history of medicinal use. Thus, only if a safety concern is
recognized or suspected, supporting non-clinical investigations may be
needed (EMEA, 2008).
In general, the combination of documented experience gained during
long-standing use with bibliographic data is the main basis of the
non-clinical assessment of traditional and well-established HMPs.
Therefore, particular attention should be paid to effects that are
difficult or even impossible to detect clinically. They include
genotoxicity, carcinogenicity, and toxicity to reproduction. Especially
the lack of data from genotoxicity testing may present a safety concern.
Thus there is a need for the assessment of the genotoxic potential of
herbal preparations. For many active substances data on genotoxicity are
missing or data described in the literature are inadequate. If an
adequate assessment cannot be made, further genotoxicity testing is
required (EMEA, 2006b).
Guidelines
on genotoxicity testing of pharmaceuticals, primarily directed to the
assessment of new chemically defined active ingredients, have been
established by ICH since the 1990s (ICH S2)
and have been adopted as EMA guideline (EMA/CHMP/ICH/126642/2008). This
guideline describes a battery approach of genotoxicity testing, in
which pro- and eukaryotic test systems in in vitro and in vivo are employed ( EMEA, 2008).
The basic requirement is to assess genotoxicity initially in a
bacterial reverse mutation test, followed by tests in mammalian cells in vitro and a mandatory test in a mammalian model in vivo.
For
HMPs, the HMPC has established a stepwise approach, in order to address
both scientific aspects of genotoxicity testing and the special needs
of HMPs within the current regulatory framework. This approach also
includes the documented history of medicinal use, with the guideline
EMEA/HMPC/32116/2005 setting the frame and the guideline
EMEA/HMPC/107079/2007 giving detailed guidance. The basic assessment is a
bacterial reverse mutation test, using a battery of different strains
as well as metabolic activation. For technical information on how to
perform this test (Ames-test; Salmonella typhimurium mutation assay) the OECD guideline no. 471 ( OECD, 1997a)
is referred to. Only in cases of equivocal or positive results, which
cannot be explained sufficiently or clearly attributed to specific
constituents with a well-known safety profile (e.g. the ubiquitous quercetin or other flavonoids common also in food), additional in vitro tests, e.g. mouse lymphoma cell assay, and, if necessary, also in vivo studies are required.
Usually,
European community herbal monographs established by the HMPC for
well-established and/or traditional use cover a range of herbal
preparations. In order to alleviate the manufacturers task of testing
their own specific preparations, a distinct guidance was developed
offering a strategy to reduce the number of test materials (EMEA, 2009).
This approach suggests testing a representative range of preparations
of an herbal drug rather than conducting individual tests as is
otherwise required – the so-called ‘bracketing/matrixing’ approach (Wiesner and Knöss, 2010).
The main objective of this guideline is to achieve consensus on a
standard range of test materials which could be considered
representative of the commonly used preparations of a herbal drug, with
the intention to facilitate providing data necessary for allowing their
entry to the Community list established by decision of the European Commission (2008/911EC).
This
guideline mentions the option to extrapolate the results obtained with a
specific preparation to closely related preparations. Only in case of
extracts prepared with ethanol/water mixtures of substantially different
concentrations, the demonstration of the phytochemical similarity of
the test materials may be required (EMEA, 2009).
This test design also assumes that the genotoxic potential of any
intermediate preparation is represented by the results of the extremes
tested.
Recently,
the conduction of a joint project for testing genotoxicity of selected
extracts using this “bracketing and matrixing” concept for more than 30
herbal drugs has been reported (Gaedcke et al., 2009 and Kelber et al., 2012).
The present paper shows the results of the practical application of the
“bracketing and matrixing” concept on a specific herbal drug,
Valerianae radix.
