1. Introduction
Hypericum perforatum L. (St. John's Wort) is native to
Europe, North Africa, and West Asia, and is also found in South
Africa, North and South America and Australia. It is a perennial
aromatic shrub that has bright yellow flowers from June to
September [1]. St. John's Wort and products containing it are
currently used, particularly in the EU and North America, for
the treatment of mild and moderate forms of depression as an
alternative to conventional antidepressant treatment [2]. The
sales figures for St. John's Wort rank it within the top ten best
selling plant medicines in Europe in 2003 [3], making the
species important both medicinally and economically. A recent
spike in sales in the UK, thought to be due to unseasonable bad
weather, has seen a 115% increase in usage for June 2012
compared to the same period in 2011 [4]. This high usage
coupled with the known interactions with other medications
[5] makes it a priority for those concerned with quality control
and consumer safety.
Within the EU, the regulations require clear plant identification
to ensure both the quality and safety of any commercial
herbal drug product [6]. Currently, herbal products are identified
through a variety of morphological and chemical characteristics.
These are detailed in the monographs that are
compiled by individual countries and regional entities such as
the European Pharmacopeia (www.edqm.eu). However, chemical
and morphological techniques cannot resolve all questions
of identity, especially when a product is powdered, mixed or
presented as a tincture. DNA-based identification methods have
been widely reported for the identification of medicinal plant
material [7–11]. The benefits of using this type of method