pigment
A pigment is a powder used to add or alter color or change visual appearance. Pigments are completely or nearly solubility, insoluble and reactivity (chemistry), chemically unreactive in water or another medium; in contrast, dyes are colored sub ...
of
lichen
A lichen ( , ) is a hybrid colony (biology), colony of algae or cyanobacteria living symbiotically among hypha, filaments of multiple fungus species, along with yeasts and bacteria embedded in the cortex or "skin", in a mutualism (biology), m ...
s in the genus ''
Caloplaca
''Caloplaca'' is a lichen genus comprising a number of distinct species. Members of the genus are commonly called firedot lichen, jewel lichen.Field Guide to California Lichens, Stephen Sharnoff, Yale University Press, 2014, gold lichens, "ora ...
Xanthoria parietina
''Xanthoria parietina'' is a common and widespread lichen-forming fungus in the family Teloschistaceae. Commonly known as the yellow wall lichen, common orange lichen, or maritime sunburst lichen, this foliose lichen, leafy lichen is known f ...
'', and a
pigment
A pigment is a powder used to add or alter color or change visual appearance. Pigments are completely or nearly solubility, insoluble and reactivity (chemistry), chemically unreactive in water or another medium; in contrast, dyes are colored sub ...
found in the roots of curled dock (''Rumex crispus''). It has an orange-yellow color and absorbs blue light.
It is also known as physcion.
It has also been shown to protect lichens against UV-B light, at high altitudes in
alpine
Alpine may refer to any mountainous region. It may also refer to:
Places Europe
* Alps, a European mountain range
** Alpine states, which overlap with the European range
Australia
* Alpine, New South Wales, a Northern Village
* Alpine National P ...
regions. The UV-B light stimulates production of parietin and the parietin protects the lichens from damage. Lichens in arctic regions such as
Svalbard
Svalbard ( , ), previously known as Spitsbergen or Spitzbergen, is a Norway, Norwegian archipelago that lies at the convergence of the Arctic Ocean with the Atlantic Ocean. North of continental Europe, mainland Europe, it lies about midway be ...
retain this capability though they do not encounter damaging levels of UV-B, a capability that could help protect the lichens in case of
ozone layer
The ozone layer or ozone shield is a region of Earth's stratosphere that absorption (electromagnetic radiation), absorbs most of the Sun's ultraviolet radiation. It contains a high concentration of ozone (O3) in relation to other parts of the a ...
cucumber powdery mildew
The cucumber (''Cucumis sativus'') is a widely-cultivated creeping vine plant in the family Cucurbitaceae that bears cylindrical to spherical fruits, which are used as culinary vegetables.fenarimol and polyoxin B.
It reacts with KOH to form a deep, reddish-magenta compound.
Effect on human cancer cells
Also found in
rhubarb
Rhubarb is the fleshy, edible stalks ( petioles) of species and hybrids (culinary rhubarb) of ''Rheum'' in the family Polygonaceae, which are cooked and used for food. The plant is a herbaceous perennial that grows from short, thick rhizomes. ...
, the orange compound appears to have potential to suppress 6-phosphogluconate dehydrogenase, or 6PGD. 6PGD is the third enzyme of the
pentose phosphate pathway
The pentose phosphate pathway (also called the phosphogluconate pathway and the hexose monophosphate shunt or HMP shunt) is a metabolic pathway parallel to glycolysis. It generates NADPH and pentoses (five-carbon sugars) as well as ribose 5-ph ...
, or PPP, an oxidative process fueling growth in a still-relatively-unknown way. But it appears that arresting the chemical machinery at its third step could be promising for oncology. The parietin, identified from an FDA database of 2,000 known suppressors of 6PGD, killed half the human leukemia cells over two days in the laboratory. The pigment also slowed the growth of other human cancer cells in mouse models, according to the study. A more-potent derivative of the parietin called S3 may even cut the growth of lung cancer cells implanted in mice by two-thirds, over the course of 11 days. The compound also appears to be non-toxic to healthy cells.