Stability of St John's Wort components in flavoured drinks
There is a growing market for food and drinks with health benefits, and
a number of popular botanicals including St John's Wort have been
used as ingredients in conventional foods or sold as "functional
foods".
A team of American and Chinese researchers have made a detailed
study of the fate of biologically active compounds in St John's
Wort at various acidity levels and under dark and light conditions.Their
results indicate just how unstable may of these active principles
are.
St John's Wort
St John's Wort is a widely used herbal antidepressant, which is
treated as a drug in Germany but as a dietary supplement in the
United States.
It contains many compounds with documented biological activities,
the main classes being naphthodianthrones (hypericin and psesudohypericin
and their precursors, protohypericin and protopseudohypericin respectively),
phloroglucinols (hyperforin and adhyperforin), flavonol glycosides
and biflavones.
A review of the literature by Ang and her colleagues indicates
that a number of studies have already shown that St John's Wort
products are unstable and that there is uncertainty as to whether
it is hypericin or hyperforin which is responsible for the its antidepressant
effects.
The objectives of Ang's study were to determine the effects
of pH and light exposure on the stability of selected, unique active
components of St John's Wort, namely pseudohypericin, hypericin, hyperforin
and adhyperforin in aqueous buffer solutions and non-alcoholic,
non-carbonated, fruit-flavoured beverages.
Results indicated that St John's Wort components were unstable
in acidic aqueous solutions. More changes were observed during
light exposure, with hyperforin and adhyperforin decreasing the
most. Less dramatic changes were seen in the fruit flavoured beverage
samples than in the buffer solution at pH 2.65.
The authors speculate that this may due to the protective effects
of other ingredients in the beverage. The major degradation products
of hyperforin in acidic aqueous solution were furohyperforin, furohyperforin
hydroperoxide and furohyperforin isomer a. This last compound was
also found in the drink product containing St John's Wort as an
ingredient.
Reference
Ang CY, Hu L, Heinze TM, Cui Y, Freeman JP, Kozak K, Luo W, Liu
FF, Mattia A, DiNovi M. (2004). Instability of St. John's wort (Hypericum
perforatum L.) and degradation of hyperforin in aqueous solutions
and functional beverage. J
Agric Food Chem, 52, 6156-6164
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