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Shiitake and porcini may be more than culinary delights.
Gourmet Medicine: Edible Mushrooms May Help Fight Cancer
by Jennifer Amie
Shiitake and porcini mushrooms are prized by cooks, but they
may provide much more than good flavor. For centuries, the healing
properties of mushrooms have been recognized by practitioners
of traditional medicine in China, Japan, and Europe. Today, Bell
Museum curator of fungi David McLaughlin, graduate student Bryn
Dentinger, and Dr. Joel Slaton of the University of Minnesota
Medical School have teamed up to investigate the cancer-fighting
properties of these delicacies.
"In Europe, porcini have been used as a cancer treatment
since the Middle Ages, and they've been used in Chinese medicine
for much longer than that," says Dentinger.
Evidence from a 1950s study at Memorial Sloan-Kettering Cancer
Center supports the theory that porcini may be quite potent. "The
study showed 80- to 100-percent inhibition of two different tumors
with extracts of Boletus edulis [porcini]," Dentinger explains.
Dentinger is providing Slaton with dried tissue from two types
of porcini mushroom: one that grows on oak trees in Minnesota
and a second that grows on West Coast conifers.
Slaton tests extracts from these samples on cancer cells grown
in the laboratory and on tumors in mice. If the extracts shrink
the tumors, Slaton will try to identify the compounds that inhibit
cancer growth.
Slaton is also studying shiitake mushrooms, which produce immune-boosting
vitamin D.
For these laboratory tests to be meaningful, Slaton must know
exactly which mushrooms he is testing. Shiitake mushrooms from
Japan, for example, may be very different from shiitake mushrooms
from Southeast Asia, Dentinger says.
Researchers not only need to know which type of mushroom they're
using in experiments, but must also be sure they're using the
same type from day to day—and therein lies the problem.
"What we think of as 'porcini' may in fact be as many as
39 different species," says Dentinger. "Though they
look alike, they may not be closely related."
Porcini cannot be cultivated and must be collected from the wild,
further complicating the task of identifying the mushrooms correctly
and consistently.
For his part, Dentinger is trying to untangle the genetic relationships
among the various mushrooms known as "porcini."
Porcini grow throughout the temperate zone of the northern hemisphere,
from Asia to Europe to North America, and are found as far south
as Yunnan, China, Himalayan India, and Costa Rica. "Everybody's
using different names for these mushrooms," says Dentinger.
Scientific names, of course, are meant to dispel such confusion
by creating a universal standard. The first time any species is
identified and named by a scientist, a specimen of that species—whether
bird or fish or mushroom—is preserved in a museum or herbarium.
Researchers can always return to this original specimen, known
as a "type specimen," for comparison when they are trying
to identify a species.
The scientific name for porcini is Boletus edulis, and it just
so happens that its type specimen is a painting. The herbarium
that contained the actual mushroom was destroyed during the French
revolution, when the botanist who named the species was killed
under mysterious circumstances. The botanist's painting of Boletus
edulis (known as an iconotype) is believed to survive in the collections
of the Muséum National d'Histoire Naturelle in Paris, and
Dentinger is trying to track it down. In the meantime, all he
has to go on is a reproduction of the painting published in 1791
in Pierre Buillard's Histoire des Champignons de la France (see
cover photo).
Unfortunately, the illustration contains no details about the
color, size, and shape of the mushroom's spores and cells—all
elements critical to proper identification of mushrooms.
While this puts Dentinger at a disadvantage as he attempts to
sort out which of his mushroom specimens are truly Boletus edulis
and which are not, he does have a modern trick up his sleeve:
genetic analysis.
Dentinger is examining DNA from porcini specimens in museums
around the world, as well as from mushrooms he's collected himself.
His goal is to extract and sequence DNA from all the various
types of porcini to sort them into species groups. He will then
be able to determine which groups are most closely related—an
important factor for biochemists trying to isolate drug compounds.
If a mushroom is found to have cancer-fighting properties, scientists
might also look to its closest relatives for medicinal benefits.
Dentinger believes that porcini and shiitake mushrooms may be
most helpful as an ingredient in our diets. "It's not clear
whether they contain something that you could synthesize as a
chemotherapy agent, or whether you could incorporate these mushrooms
into your diet and get a protective benefit," he says. "I
think their greatest potential is as delicious edible mushrooms."
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