Iodine in Sea
591
Part D | 23
23. Iodine in Seaweed: Two Centuries of Research
Frithjof C. Küpper
This paper provides a historic overview of the
research on iodine in seaweeds, starting with
historic uses of iodine-containing seaweeds in
ancient China and Greece. Iodine as a novel element was discovered by Courtois in Napoleon-era
France. This triggered research on the chemical
properties of the novel element and also started
an iodine-producing seaweed industry. However,
iodine-containing seaweeds did not receive much
academic attention until the end of the nineteenth
century, when the release of molecular iodine from
red algae was discovered, followed by similar findings in brown algae (kelp) three decades later. The
1950s saw the rise of studies of iodine uptake in
kelp, based on the availability of radioactive iodine isotopes. Since the 1970s, a wealth of studies
has investigated the emission of iodo- and other
halocarbons from seaweeds and their role in the
References................................................... 594
atmospheric and marine environments. Our group
has addressed the physiology and biochemistry of
iodine uptake in Laminaria since the 1990s. This
has established the involvement of both hydrogen
peroxide and vanadium haloperoxidases in the
process and led to the finding of iodine efflux upon
oxidative stress. X-ray absorption spectroscopy
identified the accumulated form as iodide, constituting an antioxidant protecting the cell wall space
and surface of kelp against oxidative stress. Iodide
in Laminaria constitutes the first inorganic and
chemically simplest antioxidant known from a living system. Upon exposure to atmospheric ozone,
this leads to the emission of molecular iodine and,
together with high irradiance, to the formation of
ultrafine particles.
As early as the third millennium B.C., the goiterpreventing effects of seaweeds had been known to the
legendary emperor Shen-Nung in ancient China. The
use of burnt seaweeds and sponges as diet supplements
for the same purpose was common in the era of the
Greek physician Hippocrates (460–370 B.C.; [23.1]).
However, iodine as a novel element was discovered in
the context of the Napoleonic Wars in Europe. For more
detailed historical accounts, several excellent reviews
are available (e.g., [23.2–4]). Bernard Courtois, a manufacturer of saltpeter (KNO 3 ), was trying to contribute
to the war effort – and to gain a livelihood – by obtaining saltpeter from novel sources [23.2]. When replacing
wood ashes as the raw material for soda by the ashes of
brown seaweeds (mainly Fucus sp. and Laminaria sp.,
which are abundant on rocky French Atlantic coasts)
in (probably November) 1811, his copper vessels not
only underwent strong corrosion, but the addition of
concentrated sulfuric acid also resulted in the emission
of a previously unobserved violet vapor based on the
reaction
2I
C H 2 SO 4 ! I 2 C SO 3
2
C H 2 O :
Tragically, Courtois was not able to pursue his research on this new substance himself due to a lack of
money and 2 years passed. Still, he managed to incite Charles Bernard Desormes and Nicolas Clément,
two of his chemist friends, to pursue the work, together with André M. Ampère and the most eminent
French chemist of that era, Joseph Louis Gay-Lussac.
On behalf of Courtois, Clément also presented the findings to the Imperial Institute of France (Conservatoire
des Arts et Métier, where he held a professorship) on
November 29, 1813, which led to their original publication in the Annales de Chimie [23.5]. Based on
the Greek à J
!ıÁ& i. e., violet, due to the beautiful violet color of its vapor, the name iode was already
used in this paper for the new substance. It also mentions the metal-like appearance of its solid, elemental
591
Part D | 23
23. Iodine in Seaweed: Two Centuries of Research
Frithjof C. Küpper
This paper provides a historic overview of the
research on iodine in seaweeds, starting with
historic uses of iodine-containing seaweeds in
ancient China and Greece. Iodine as a novel element was discovered by Courtois in Napoleon-era
France. This triggered research on the chemical
properties of the novel element and also started
an iodine-producing seaweed industry. However,
iodine-containing seaweeds did not receive much
academic attention until the end of the nineteenth
century, when the release of molecular iodine from
red algae was discovered, followed by similar findings in brown algae (kelp) three decades later. The
1950s saw the rise of studies of iodine uptake in
kelp, based on the availability of radioactive iodine isotopes. Since the 1970s, a wealth of studies
has investigated the emission of iodo- and other
halocarbons from seaweeds and their role in the
References................................................... 594
atmospheric and marine environments. Our group
has addressed the physiology and biochemistry of
iodine uptake in Laminaria since the 1990s. This
has established the involvement of both hydrogen
peroxide and vanadium haloperoxidases in the
process and led to the finding of iodine efflux upon
oxidative stress. X-ray absorption spectroscopy
identified the accumulated form as iodide, constituting an antioxidant protecting the cell wall space
and surface of kelp against oxidative stress. Iodide
in Laminaria constitutes the first inorganic and
chemically simplest antioxidant known from a living system. Upon exposure to atmospheric ozone,
this leads to the emission of molecular iodine and,
together with high irradiance, to the formation of
ultrafine particles.
As early as the third millennium B.C., the goiterpreventing effects of seaweeds had been known to the
legendary emperor Shen-Nung in ancient China. The
use of burnt seaweeds and sponges as diet supplements
for the same purpose was common in the era of the
Greek physician Hippocrates (460–370 B.C.; [23.1]).
However, iodine as a novel element was discovered in
the context of the Napoleonic Wars in Europe. For more
detailed historical accounts, several excellent reviews
are available (e.g., [23.2–4]). Bernard Courtois, a manufacturer of saltpeter (KNO 3 ), was trying to contribute
to the war effort – and to gain a livelihood – by obtaining saltpeter from novel sources [23.2]. When replacing
wood ashes as the raw material for soda by the ashes of
brown seaweeds (mainly Fucus sp. and Laminaria sp.,
which are abundant on rocky French Atlantic coasts)
in (probably November) 1811, his copper vessels not
only underwent strong corrosion, but the addition of
concentrated sulfuric acid also resulted in the emission
of a previously unobserved violet vapor based on the
reaction
2I
C H 2 SO 4 ! I 2 C SO 3
2
C H 2 O :
Tragically, Courtois was not able to pursue his research on this new substance himself due to a lack of
money and 2 years passed. Still, he managed to incite Charles Bernard Desormes and Nicolas Clément,
two of his chemist friends, to pursue the work, together with André M. Ampère and the most eminent
French chemist of that era, Joseph Louis Gay-Lussac.
On behalf of Courtois, Clément also presented the findings to the Imperial Institute of France (Conservatoire
des Arts et Métier, where he held a professorship) on
November 29, 1813, which led to their original publication in the Annales de Chimie [23.5]. Based on
the Greek à J
!ıÁ& i. e., violet, due to the beautiful violet color of its vapor, the name iode was already
used in this paper for the new substance. It also mentions the metal-like appearance of its solid, elemental