CHAPTER 2
REVIEW OF RELATED LITERATURE
This chapter provides the related literatures about the problem presented which
serves as its basis for its underlying principles on the study
.
Red Onions
Books sources:
According to Duke, 2003, Allium cepa, commonly termed as onion; in Filipino
terms—Sibuyas; in Bisayan—Cebuyas Bombay and; in Ilocano—Lasona. It belongs to
the family Mililiaceae and has been widely use for culinary and medicinal purposes. The
dried outer skin of the bulb reduces a bacteriocide and an excellent yellow dye. The
sscales outside the onion bulb are one of the richer sources of quercetin, a very useful
phytochemical also shared with evening primrose. Scales contain a heart stimulant that
increases pulse volume, affects the uterus, promotes bile production, and reduces blood
sugar. Onion bulbs are said to be aphrodisiac, diuretic, expectorant, emmenagogue,
hypoglycaemic, and stimulant (MPI). Onion juice and EO demonstrated antiaggregant
and hypocholesterolemic activities in humans subjects (MPI). Onions are alleged to
stimulate bile production, to speed healing of gunshot wounds, and to cure scorpion
bites, freckles, and the common cold.
Libster, 2000 stated that Asian Indians eat raw onions, spiced up with lemon,
pepper, and salt, for bronchitis, colic, edema, fever, and scurvy. Some people with
parasites macerate an onion in white wine and drink it on an empty stomach in the
morning. Or pediatric patients drink water in which onion has stepped overnight to kill
parasites. Cooked onions are consumed by Japanse macrobioticists to calm the
nervous system and alleviate irritability and sore muscles after heavy labor. A cut raw
onion is placed under the pillow to aid insomnia. Reputed to be hypotensive, onions
have recently been shown to contain the antihypertensive agent prostaglandin A1, but
only at ca. 1 ppm. With prostaglandins like this going at $10 per milligram, that means
that a kilogram of onions (now costing about $1) contains $10 worth of prostaglandin.
Add that to your chicken soup. Juice of the bulb is used for coughs and earache.
Macerated in ginm the bulbs are used for dropsy and gravel (GMH). In India, onions are
believed to be aphrodisiac, especially if retained in a cow dung year in a well-stoppered
pot for four months (DEP). Even wilder, in an Indian formula for acute dysentery, one
buries a grain of opium in an onion bulb and then roasts the onion (DEP). Most of the
real and folk medicinal attributes of onion are shared with garlic and other lesser known
members of the genus Allium. Garlic is popular with organic gardeners and naturopaths
for its biological activities. For millennia, onions have been famous for food, condiments,
and medicine. Green onions are eaten raw with meats, fish, cheese, or as a vegetable,
or chooped and added to cottage cheese, or cooked. Onions are eaten raw, boiled,
baked, creamed, broiled, fried, French-fried, roasted, or pickled, and in soups, stews,
dressings, or salads, but perhaps more importantly, added to other ingredients for
innumerable dishes. Dry onions may be served as a vegetable dish or to flavour meat,
fish, and poultry dishes and are also used in salt substitutes such as Spike, Mrs.Dash
and Vegit. A thick layer of cooked onion is used on the French dish pissaladiere,
sometimes called “Provencal pizza” (FAC). Onions are used in the Catalan sauces
sofregit and samfaina (FAC). In Tunisia, a fermented onion paste called “hrous” is used
to flavour couscous, soups, and stews (FAC). The papery outer skins, called “shuski” in
slavic Macedonia, are used as a dye for coloring Easter eggs, and in Egypt they are
used to color and flavour eggs called “hamine” (FAC). The leaves of some cultivars are
widely used as scallions. In Catalonia, the large shoots called “calcots” or “sprunzale”,
sprouted from bulbs planted in trenches, are blanched and eaten raw with bread, grilled,
or used for flavouring beans and sauces (FAC). Sprouted seeds used in salads and on
sandwiches.
Willey & Sons, 2002, stated that two flavonoid subgroups are found in the onion,
the anthocyanins, which impart a red/ purple color to some varieties and flavonols such
as quercitin and its derivatives responsible for the yellow and brown skins of many
varieties.
Journals sources:
According to Asis, 2001, onion is biennial plant which may persists vegetatively
as a perennial by means of bulbs. The root system is relative shallow and fibrous. The
underground stem is short and subconal; from it hallow cylindrical leaves are diverged
in one-half phyllotaxy (leaf arrangement). The sheathing base of each leaf completely
encircles the short stem, and it is this development of the fleshy leaf bases, together
with the absence of intermodal elongation, that results in the formation of the
commercial bulb. Onion is grown locally on a limited scale and gives good returns
although much labor is required in the cultivation. Crops produced in the Philippines are
relatively poor in quality and rot more quickly and storage. This may be related to the
short natural light period in the tropics during the time of bulbing. The water requirement
increases during the bulbing time. The bulbs need about two months storage at 4.4°-
10°C before planting. Red Bermuda or sibuyas Bombay is better adapted to our
conditions than the granex or excel variety but is off poorer keeping quality and more
pungent. Commercial production of onions is restricted to definite seasons. The cooler
months (Nov.-Jan.) are the planting months; the harvest takes place during the dry and
warm months (March- May).
On the study conducted by Lanzotti, 2006, onion is characterized by polar
compounds of phenolic and steroidal origin, often glycosilated, showing interesting
pharmacological properties. The flavonoids in onion tend to be more concentrated in the
outer layers of the flesh.
Agric, 2007, mentioned that the qualitative anthocyanin content of red onion
cultivars includes a wide structural assortment including several unique flavonoid
structure. Red onion is a rich source of anthocyanin. The index onion cultivars
according to their content of flavonoids measured as quercetin. The only compound
belonging to flavonols, anthocyanins, and the dihydroflavonols have been report to
occur in onion bulb. Red onion contains 415-1917 mg of flavonols per kilogram of FW.
Flavonols are the predominant pigments of onion. The anthocyanin of red onion is
mainly cyaniding glycosides acylated with malonic acid or non-acylated. The quantities
content of anthocyanin in some red onion cultivars has been reported to be
approximately 10% of the total flavonoid content or 39-240 mg kg -1.
Internet sources:
Onion is an olfactory indicator. The onion odor isn't detectable in strongly basic
solutions. Red onion can act as a visual indicator at the same time. It changes from pale
red in acid solution to green in basic solution (antoine.frostburg.edu retrieved: 2/10/13).
On the other hand, World Health Foods states that onions are members of the
Allium family that are rich in sulfur-containing compounds that are responsible for their
pungent odor and for many of their health-promoting effects. Onions are an outstanding
source of polyphenols, including the flavonoid polyphenols which makes it a standout
source of quercetin. The flavonoids in onion tend to be more concentrated in the outer
layers of the flesh. In animal studies, there is evidence that onion’s sulfur compound
may work in an anti-clotting capacity and help prevent the unwanted clumping together
of blood platelet cells. It can also lower blood levels of cholesterol and triglycerides and
improve cell membrane function in red blood cells. In human studies, onion provides
protection for the heart and blood vessels when consumed in a diet that is rich in other
vegetables and fruits – especially flavonoid-containing vegetables and fruits. It can also
increase our bone density and provide direct benefits to our connective tissue due to its
high sulfur content (whfoods.com retrieved Jan.2013).
Anthocyanins
Books sources:
Harborne, 2000, mentioned that lycopene, saponins, tannins, anthocyanin, and
flavonoids are the usual components commonly seen in the of leaves, fruits, trunks,
peels, roots of plants like guava, tomato, garlic, onions, atis and cabbage. Anthocyanins
are all based chemically on a single aromatic structure, that of cyaniding, and all are
derived from this pigment by addition or subtraction of hydroxyl groups or by
methylation or by glycosylation. Orange-red colours are due to pelargonidin with one
less hydroxyl group than cyaniding, while mauve, purple and blue colours are generally
due to delphinidin, which has one more hydroxyl group than cyaniding.
According to Willstatter, 2003, nearly any fruit or flower that is bright red, blue or
purple contains pigment molecules that are based on cyanidin. The molecular structure
is responsible for all these colors. like phenolphthalein, cyanidin’s structure changes
with pH. In acidic solution, there is a high formal charge on the oxygen in the structure
which makes it bright red. In basic solution, removal of hydrogen from the OH group on
the right outmost ring and forms a blue or violet color. In natural forms of the molecule,
the hydrogens on at least one of the -OH groups are replaced with more sugar
molecules. A cyanidin with attached sugars is called an anthocyan or anthocyanin.
Guevarra, 2005 added that anthocyanins also make up the most important and
widespread group of coloring matter in plants. It is one of the subclass of the phenolic
compound named flavonoids.
Journals sources:
In a research article entitled, “Use Of Anthocyanin Extracted From Natural Plant
Materials To Develop A Ph Test Kit For Measuring Effluent From Animal Farms”,
Suppadit et al., 2011, Anthocyanins (from the Greek anthos = flower and kianos = blue)
are the most important pigments of the vascular plants; they are harmless and can be
easily incorporated into aqueous media which makes them interesting for use as natural
watersoluble colorants. These pigments are responsible for the shiny orange, pink, red,
violet and blue colors in the flowers and fruits of some plants. Anthocyanins can be
found in different chemical forms depending on the pH of the solution. In the research,
two factors were considered in optimal extraction of anthocyanin. First, the type of
natural plant materials is considered. The research utilized butterfly pea (Clitoria
ternatea L.) flower roselle red (Hibiscus sabdariffa L.) flower and dragon fruit
(Hylocereus undatus (Haw) Britt. &Rose.) peel. Second is the type of solvent to be
used. This includes consisting of distilled water, 1% HCl/95% ethanol, 0.1 N acetic
acid, 0.5% vinegar and 20% white liquor. The butterfly pea flowe yielded the highest
amount of anthocyanins at 541mg/100 g dry weight followed by roselle red flower (280
mg/100 g) and dragon fruit peel. For solvents, the distilled water used for the extraction
yielded the highest amount of anthocyanins (394 mg/100 g dry weight) followed by
white liquor (388 mg/100 g), 1% HCl/95% ethanol (303 mg/100g), acetic acid (288
mg/100 g) and vinegar (282 mg/100 g) (P<0.05).
From a journal written by Frosburg, 2001 he mentioned that any substance that
undergoes a reversible chemical change when pH changes can be used as an acid-
base indicator. In practice, a sharp change in some easily detectable property of the
substance is required. Usually, the property is color; but other properties such as odor
can also change with pH. Almost any flower, fruit, or plant part that is red, blue, or
purple contains a class of chemical compounds called anthocyanins that change color
with pH. The color of a flower or fruit depends on which anthocyanins are present, the
pH of the pigment-bearing tissues, and the presence of other pigments, like yellow
flavones. Red cabbage contains a mixture of anthocyanins and other pigments that
indicate a wide range of pH.
Accorrding to Medwell Journals, 2010, despite their advantages with respect to
heat, light, ph ability and purity, compared with natural colorants such as anthocyanins,
synthetic pigments are increasingly rejected by consumers owing to health concerns,
thus there is worldwide interest in additional use of anthocyanins as consequence of
perceived consumer preferences as well as legialative action which has continued the
delisting of approved artificial dyes. The onion solid wastes was frozen with liquid
nitrogen and ground with a pestle and a mortar. An amount of approximately 500
milligrams of ground tissue was place in a 30 ml glass vials and 10 ml of solvent was
added. Extraction was carried under magnetic stirring at 400 rpm at room temperature
for predetermined time periods. Upon completion of extraction, the extract were filtered
through paper filter and stored at negative 20°C until analyzed. All extracts were also
filtered through 0.45 micrometer syringe filters prior to determinations. Briefly an aliquot
of extract was combined with ethanolic HCL solution (0.25M) to give a dilution 1:10. The
solution was mixed thoroughly and the absorbance at 520 nm was read after 5 mins
using the ethanolic HCL solution as blank. Total anthocyanin content was determined
as cyanin per 100 g fresh tissue using as ɛ= 26900 and MW=449.2.
Anthocyanin was also extracted from rose petals to be used as acid-base
indicators as describe by Vankar & Majpai, 2010, anthocyanin extraction were carried
out by three methods. By 1) HCl, 2) Citric acid 3) Tatrtaric acid. 1) Anthocyanins were
extracted from flowers with 0.1% HCL in methanol for two to three hours at room
temperature in darkness. The mixture was filtered on a Buchner funnel and the
remaining solids were washed with 0.1% HCl in methanol until a clear solution was
obtained. The combined filtrates were dried using a rotary evaporator at 30°C. The
concentrate was dissolved in 0.01% HCL in DW and in the solution was used as
indicator. 2) Anthocyanins were extracted from flowers with 4.0% citric acid in methanol
for 2-3 hours at room temperature in darkness. The mixture was filtered in a Buchner
funnel and the remaining solids were washed with 4.0% citric acid in methanol until a
clear solution was obtained. The combined filtrates were dried using a rotary evaporator
at 30°C. The concentrate was dissolved in 4.0% citric acid in DW and in the solution
was used as indicator. 3) Anthocyanins were extracted from flowers with 4.0% tartaric
acid in methanol for 2-3 hours at room temperature in darkness. The mixture was
filtered in a Buchner funnel and the remaining solids were washed with 4.0% tartaric
acid in methanol until a clear solution was obtained. The combined filtrates were dried
using a rotary evaporator at 30°C. The concentrate was dissolved in 4.0% tartaric acid
in DW and in the solution was used as indicator.
Electronic Journal of Environmental, Agriculture and Food Chemistry, 2010,
added that anthocyanin changes color when the ph is 2-9 and the color will be from dark
pink to mehdi green. Phenolphthalein is an organic compound (C20H14O4) used as an
acid-base indicator.
Internet sources:
Anthocyanins are water soluble pigment that provides color to plants. The cyan
part of the name comes from the Greek word for blue, and cyan is also a
complementary color of red. Some good food sources of anthocyanins are eggplant,
checkberries, cherries, elderberries, red grapes, blueberries, oranges, red onion, red
wine, strawberries, radishes and purple cabbage (thirdplanetfood.com , r etrieved 2013).
Anthocyanins are contained in red, purple, and blue colored flowers, fruits,
leaves, and roots of higher plants. They mainly exist as glycosides in plants and their
aglycon. Anthocyanidin is a chromophore in pigments. It change thie color with pH like
litmus form flavylium ions strongly acidic solutions resulting in a very stable orange to
red. In weakly acidic or neutral solutions they first begin to form anhydrobases, so that
the color is reddish violet to violet. The blue they produce in alkaline media is the
predominance of anhydrobase anions. However, anhydrobases and anhydrobase
anions are unstable and are easily hydrated at the 2-position of the anthocyanidin
nucleus, resulting in a rapid change to the colorless pseudobase (crcnetbase.com,
retrieved 2011).
According to math.ufl.edu, retrieved 2010, Anthocyanins have played a
prominent role in the enrichment of human lives for thousands of years. Historians and
scientists believe that cave paintings from as far back as 15,000 B.C.E. were colored
using various plant pigments, and in Egypt and China, dyed fabrics have been found
and dated back to 2,000 B.C.E. The ancient Britons used a blue plant dye to color their
bodies in an attempt to frighten enemies in battle, and more recently in history, the
famous “red coats,” worn by British soldiers in the American Revolutionary War, were
dyed with a plant called ‘madder root’. Richard Martin Willstätter was the first scientist to
identify anthocyanins as the primary red/blue pigmentation in some plants and fruits. He
received the Nobel Prize in Chemistry in 1915 for his work with chlorophyll in connection
to anthocyanins and plant coloring. Specifically, he isolated the characteristic pigment in
cornflowers, roses, pelargonias, larkspurs, and hollyhock, and showed that
anthocyanidins attached to glucoses produced an anthocyanin. Willstätter also
explained how the same anthocyanin can have blue or red color properties, and
proposed that in roses the anthocyanin is bonded to a plant acid, which makes it red.
Conversely, he claimed, in cornflower, the anthocyanin is bonded to a plant alkali, which
is why it is distinctly blue.The word anthocyanin is derived from two Greek words,
anthos, which means ‘flower’, and kyáneos, which means ‘purple’. Nearly three
hundred different anthocyanins have been discovered, and different fruits and
vegetables have their own signature mix of pigments. Red wine, for example, contains
over fifteen different anthocyanin compounds, depending on the amount and type of
grapes with which it is made. The differing concentrations and types of compounds are
what give wine its different color shades. Anthocyanins are also thought to play an
important role in the high antioxidant levels in fruits and vegetables. Blueberries, for
example, contain a very high concentration of antioxidant compounds, which guard the
cell walls of the berry from harmful free radicals existing inside the plant. When people
ingest blueberries, they obtain the same protection from free radicals, which can be just
as harmful to cell membranes as cell walls. Blueberries, cranberries, and cherries can
contain up to 400mg of antioxidants per 100g of berry, and concord grapes—used in
many red wines—can contain up to 750mg per 100g of grape (Sriram, 2004). In the
twelfth century, bilberry (Vaccinium myrtillus) was used as an herbal medicine to induce
menstruation, and during World War II, British pilots took the same drug before
nighttime missions to enhance their night-vision. Now, researchers know that although
anthocyanins probably cannot increase nighttime awareness, nor encourage
menstruation, they can prevent oxidation damage in both large and small blood vessels
because of their anti-oxidant properties. Anthocyanins are also believed to inhibit
degenerative nerve damage, and in laboratory conditions, delphinidin and cyanidin
compounds have been found to inhibit the epidermal growth factor receptor in cancer
cells, which could potentially stunt the growth of tumor cells in humans. Also under
study are anthocyanins’ abilities to reduce LDL (the “bad”) cholesterol, and prevent
blood clotting.
In organic compounds, conjugated (alternating double) bonds primarily affect the
color the compound absorbs. In phenolphthalein, every carbon except for the central
carbon has overlapping p-orbitals, whichcreate pi bonds between these carbon atoms.
The light absorbed by this structure is actually in the ultraviolet range, reflecting in the
infrared range, which is why phenolphthalein in a pH below 8.2 appears clear. When
Phenolphthalein is in the presence of an alkali, the hydrogen atoms in phenolphthalein’s
Hydroxide ions are removed first. In a solution with a pH higher than 8.2, the structure
opens up, and the central carbon acquires a pi bond. Because electrons are less
confined in pi bonds than sigma bonds, the absorption for this molecule shifts
bathochromically to the blue-green range of the visible spectrum (redder than ultra-
violet), which makes the light it reflects pink. Anthocyanins, because of their hydroxide
groups, can act much the same way as phenolphthalein and other weak-acid indicators.
In an alkaline solution, H+ ions from the anthocyanin are removed by excess hydroxide
ions. This allows electrons in the anthocyanin to spread out in oxygen’s p-orbitals,
causing a hypsochromic shift, but also leaving a bonding site open. Metal ions such as
Mg2+ , Fe2+ , Fe3+, Ca2+,and Al3+ are known to bond with anthocyanin compounds,
and the addition of these metal ions could cause a change in color as well. Some of
these metals will chelate with multiple anthocyanins, which can produce a very different
color than is typically exhibited by the metal ion, or the anthocyanin itself. This also
emphasizes the idea that chelation requires a pH above the pKa of the phenolic group,
because the H+ ions need to be removed for the metal ion(s) to have an open bonding
site. Because the acidified anthocyanins are generally accepted as red in color,
deprotonated anthocyanins must be present either alone, or chelated with certain metal
ions to change the color.
Fecal Occult Blood
Books sources:
Strasinger & Di Lorenzo, 2008 mentioned that by far the most frequently
peroformed fecal analysis is the chemical screening test for the detection of occult
(hidden) blood. Since, any bleeding in excess of 2.5 ml/150 g of stool is considered
pathologically significant, and no visible signs of bleeding may be present with this
amount of blood, fecal occut blood testing (FOBT) is necessary. Originally used
primarily to test suspected cases of gastrointestinal diseases, FOBT has currently
becaome widely used as a mass screening procedure for the early detection of
colorectal cancer. Annual testing for occult blood has high positive predictive value for
detection of colorectal cancer in the early stages and is recommended by the American
Cancer Society, particularly for persons older than age 50. The most frequently
encounterd screening test for occult blood are based on detection of the
pseudoperoxidase activity of hemoglobin. This is the same principle as the reagent strip
test for urinary blood, but uses a different indicator chromogen. The reaction uses the
pseudoperoxidase activity of hemoglobin reacting with hydrogen peroxide to oxidize a
colorless compound to a colored compound.
Hemoglobin H2O2 (pseudo peroxidase) Guaiac Oxidized guaiac + H2O (blue color)
However, blood presumptive test can rule out the possibility if the fluid studied is
blood. These tests relies on the use of chemicals that will change color when in the
presence of blood like phenolphthalein which turn from colorless to pink when added to
feces (Lerner & Lerner, 2006).
Journals sources:
According to National Cancer Institute, fecalysis is a major test that is least
invasive and more affordable screening test for colorectal cancer. The presence of fecal
occult blood is what should be detected because presence of blood in stool may be the
only symptom of colorectal cancer (webMD.com, retrieved January 27, 2011). There is
now strong evidence that screening for colorectal cancer with fecal occult blood tests
(FOBTs) is effective in reducing the incidence and mortality of this disease (Department
of Medicine (Gastroenterology), 2002).
According to Higaki & Philip, 2001 it has been known for many years that fecal
occult blood test shows considerable peroxidise like enzymatic activity and therefore in
the presence of hydrogen peroxide will give highly coloured products with certain
substrates and in particular, with amines such as benzidine. On their study shows the
relative merits of using benzidine and phenolphthalein as reagents in indicator test for
blood centers primarily on the sensitivity, stability and specificity of two substrates.
Results indicate that the enzyme peroxidise, which is widely distributed in plants, does
not contribute to false positive results in the three-stage phenolphthalein indicator test
for blood stain. The phenolphthalein reagent was prepared. Serial dilutions of fresh
human, neat to 0.2 x 10-6 were prepared and tested and directly in solution form and in
stain form. The direct test in stain form consisted of application of reagents to a stained
thread on filter paper. The stains have been air-dried for 24 hours. Regardless of the
means of application, phenolphthalein compared quite favorable with benzidine for
detecting blood in solution. The peroxidase based test were sensitive to diltuons of 10 -4
to 10-5 approximately equivalent to benzidine, while tests using sodium perborate all
surpassed this sensitivity of benzidine. For detecting blood in stain form, the peroxide
based test had a maximum sensitivity of 10-3. The use of perborate did not measurably
increase this sensitivity when directly testing dried stains. Benzidine was100 times more
sensitive with an end point of 10-5.
In the article of Allison, 2007, it stated that fecal occult blood testing remains an
important screening option for colorectal cancer. Furthermore, it also states that it was
no surprise to the gastroenterology community that a one-time test—colonoscopy—
would be better than a one-time sigmoidoscopy or one-time FOBT, but the press and
public interpreted this information as “If a person is screened with a test other than
colonoscopy there is a good chance he or she will die from a missed colorectal cancer.”
The evidence suggests, however, that if the other available screening tests are
employed as recommended, the incremental benefit of colonoscopy in decreasing
patient mortality from colorectal cancer is small. The concern about missed “advanced
neoplasms” in once-only testing with methods other than colonoscopy may not be as
important as it has been portrayed. Annual FOBT testing and flexible sigmoidoscopy
every 5 years are the current recommendations, leaving the potential for discovery of a
missed advanced neoplasm on subsequent screens before it has become malignant or
lethal.
Paimela et al., 2010 stated that Faecal occult blood test (FOBT) screening has
been shown to decrease the incidence and mortality from colorectal cancer. This study
compared the stage profile of patients with colorectal cancer diagnosed at the first
FOBT screening round with that of an unscreened control group.
Internet sources:
Fecal occult blood indicates the blood found in the feces that is apparently not
visible with the naked eye. Fecal occult blood test is used to detect the hidden blood in
the stool and a positive result suggests a blood loss or bleeding in the gastrointestinal
tract. Blood may appear in the stool because of one or more conditions, such as benign
or malignant growths or polyps of the colon, hemorrhoids (swollen blood vessels near
the anus and lower rectum that can rupture causing bleeding), anal fissures, intestinal
infections that cause inflammation, ulcers, ulcerative colitis, Crohn’s disease,
diverticular disease caused by outpouchings of the colon wall, abnormalities of the
blood vessels in the large intestine, and Meckel’s diverticulum. (webmd.com, retrieved
02/10/13).
Detection of blood is not only done on the diagnosis of diseases but can also be
performed in solving crimes. One the classic tools in analyzing evidence at a crime
scene is the Kastle-Meyer test for the presence of blood. A spot that might be blood is
wiped with a cotton swab to collect some of the substance. A drop of phenolphthalein
reagent is added to the sample, then a drop of hydrogen is applied to the swab. If the
swab turns pink rapidly, it is said to test positive for blood. The test result is actually
presumptive positive, meaning it is not a conclusive test for blood, and other analyses
would typically be carried out to confirm the presence of blood. Fecal occult blood test
relies on the iron in the hemoglobin, which is the iron-containing portion of a red blood
cell, to promote the oxidation of phenolphthalein to phenolphthalein. Phenolphthalein is
colorless, but in the presence of blood and hydrogen peroxide, it changes to
phenolphthalein, which makes the solution pink (sciencebuddies.org, retrieved
2/8/2013).
Guaiac’s Test
Books sources:
According to Starsinger & Di Lorenzo, 2008 many commercial testing kits are
available for occult blood testing with guaiac reagent. The kits contain guaiac-
impregnated filter paper, to which the fecal specimen and hydrogen peroxide are added.
Two or three filter paper areas are provided for application of material taken from
different areas of stool, and positive and negative controls are also included. Obtaining
samples from the center of the stool avoids false-positive from external contamination.
Addition of hydrogen peroxide to the back of the filter paper that contains the stool
produces a blue color with guaiac reagent when pseudoperoxidase activity is present.
However, Turgeon, 2008 state that various interfering substances may give false
positive results. These are mostly enzyme peroxidase from hemoglobin and myoglobin
found in red meat, vegetables like horseradish, turnips and brocoli, and fruits like
bananas, black grapes, pears, plums and melons. In addition, WBCs and bateria also
have peroxidase activity.
According to Harborne, 2000 most test for occult blood in feces is gum guiac, a
phenolic compound that produces a blue color when oxidized. The test requires the
presence of hydrogen peroxide or a suitable precursor. The peroxidase activity of the
hemoglobin molecule results in the liberation of oxygen.
Journals sources:
According to Dr. Winchester and Wansbrough 2003, guiac’s tests rely on the fact
that heme can catalyze the breakdown of hydrogen peroxide. As the H2O2 breaks
down, another substance in the reaction mixture is oxidized, producing a color change.
It is important to note that a positive test does not mean that a given stain is blood, let
alone that it is human blood, as various enzymes and certain metals can also give
positive results.
However, heme is present in red meat and peroxidase activity is present in fresh
fruits and vegetables such as radishes, turnips and broccoli. These foods, therefore,
have the potential to produce false-positive results (Alliso, 2004).
In an article by Allison, 2007, it was mentioned that in 1985, Simon published an
excellent review of FOBT testing for colorectal cancer. He stated that the concept of
occult blood detection is generally credited to Van Deen, who in 1864 used gum guaiac,
as an indicator reagent. The guaiac FOBTs (GT) detects the peroxidase activity of
heme either as intact hemoglobin or free heme. In the presence of heme and a
developer (hydrogen peroxide) guaiac acid is oxidized producing a blue color. In
screening for colorectal neoplasms a true positive GT is one which indicates bleeding
from a colon cancer or polyp. All other positive results are considered to be false
positive. Heme is present in red meat and peroxidase activity is present in fresh fruits
and vegetables such as radishes, turnips and broccoli. These foods, therefore, have the
potential to produce false-positive results. Although there are several available GTs only
three, Hemoccult II, Hemoccult Sensa (Beckman Coulter Inc.; PrimaryCare Diagnostics,
Los Angeles, CA), and hema-screen (Immunostics, Ocean, NJ), have been extensively
evaluated in large screening populations. The Hemoccult test first became available
around 1970 and was in use until modifications in 1977 led to the Hemoccult II test.
Each Hemoccult II and Hemoccult Sensa slide has two windows of guaiac impregnated
paper, on which a small amount of stool is smeared. This is repeated with two
subsequent bowel movements. The three-slide package is then returned to the
laboratory or physician’s office for development. It is important to remember that
screening for colorectal cancer with FOBT should not be done with stool samples
obtained at a digital rectal examination (DRE). FOBT results of a single stool sample
obtained by DRE should be considered inadequate screening as there is a possibility of
an increased false positivity rate and a decreased sensitivity when compared to the
standard three specimen requirement (16,17).
Internet sources:
Guaiac Test is a test for blood in urine or feces using a reagent containing
guaiacum that yields a blue color when blood is present (http://en.wikipedia.org, ret.
2013). But the fecal occult blood test results are largely affected by how an individual
prepare oneself for the test. Do not perform the test if one has diarrhea, colitis,
constipation, diverticulitis, ulcers, hemorrhoids, flare-ups, and menstrual period.
Because certain foods can alter the test results, a special diet is often recommended for
48 to 72 hours before the test. The following foods should not be eaten 48 to 72 hours
before taking the test: Beets, Broccoli, Cantaloupe, Carrots, Cauliflower, Cucumbers,
Grapefruit, Horseradish, Mushrooms, Radishes, Red meat (especially meat that is
cooked rare), Turnips, and Vitamin C-enriched foods or beverages
(http://www.webmd.com/colorectal-cancer/guide/fecal-occult-blood-test retrieved:
2/8/13).
Colorectal Cancer
Book source:
Colorectal cancer (CRC) is the second leading cause of cancer death among
men and women combined in the United States and is the third most common cause of
cancer, separately, in men and in women. The lifetime risk if developing CRC is 1:18.
Surgery will cure almost 50% of all diagnosed patients, although almost 80,000 people
develop metastatic CRC each year. The incidence of colon cancer is higher in the more
economically developed regions, such as the United States or Western Europe, than in
Asia, Africa, or South America. Although certain conditions predispose patients to
develop colon cancer, up to 70% of patients have no identifiable risk factors. Such are
age, ethnicity, personal history and tobacco use. Obesity also is a risk factor
considering dietary factors, calcium deficiency, micronutrient deficiency and such. The
pathophysiology of the disease reveals that more than 90% of CRC is adenocarcinoma.
Colon carcinogenesis involves progression from hyperproliferative mucosa to polyp
formation, with dysplasia, and transformation to non-invasive lesions and subsequent
tumor cells, with invasive and metastaic capabilities. The screening tests for early
detection of colorectal cancer have been developed by several professional societies.
Any positive or abnormal screening test should be followed up with colonoscopy
( Abraham, 2010)
According to McPherson & Pincus, 2011 the idea is that if blood is discovered in
the stool, there is the chance that a colonic tumor is the cause, and further workup, such
as colonoscopy, is therefore strongly recommended.
Journal source:
According to World Health Organization, 2008 statistics, there are many factors
contributing to colorectal cancer, the main only are tobacco use, alcohol use, unhealthy
diet and physical inactivity.
Internet source:
A stool test is one of many tests used to look for colorectal cancer. These tests
may find cancer early, when treatment works better. Colorectal cancer affects the large
intestine (colon ) and the rectum. There are three kinds of stool tests: Fecal
occult blood test (FOBT). Fecal immunochemical test (FIT). Stool DNA test
(sDNA). Blood in the stool may be the only symptom of colorectal cancer, but not all
blood in the stool is caused by cancer. Other conditions that can cause blood in the
stool include: 1) Hemorrhoids. These are enlarged, swollen veins in
the anus. Hemorrhoids can form inside the anus (internal hemorrhoids) or outside of the
anus (external hemorrhoids). 2) Anal fissures. These are thin tears in the tissue that
lines the anus (anal sphincter) up into the anal canal. 3) Colon polyps. These growths of
tissue are attached to the colon and often look like a stem or stalk with a round top. 4)
Peptic ulcers. These sores form when the digestive juices made in the stomacheat
away at the lining of the digestive tract. 5) Ulcerative colitis. This type of inflammatory
bowel disease (IBD) causes inflammation and sores (ulcers) in the inner lining of the
colon and rectum. 6) Gastroesophageal reflux disease (GERD). This is the abnormal
backflow (reflux) of food, stomach acid, and other digestive juices into the esophagus.
7) Crohn's disease. This type of inflammatory bowel disease causes inflammation and
ulcers that may affect the deep layers of the lining of the digestive tract. 8) Use
of aspirin or nonsteroidal anti-inflammatory drugs (NSAIDs). Stool tests may be used to
check for colorectal cancer, but they are never used to diagnose it. Other tests for
colorectal cancer include flexible sigmoidoscopy, colonoscopy, and CT
scan (virtual colonoscopy) (http://www.webmd.com/colorectal-cancer/fecal-occult-blood-
test-fobt retrieved: 2/9/13).
Peroxidase and Hydrogen peroxide
Books sources
Peroxidases are enzymes that belong to class I of enzymes—the
oxidoreductases. These enzymes catalyze oxidation-reduction reactions. Oxidation
means the loss of electrons, and reduction means the addition of electrons. Many
different electron acceptors are used in biological systems. Similar mechanism is seen
in the cell’s peroxisomes which have catalase, a heme enzyme, that catalyzes the
conversion of hydrogen peroxide to water and oxygen (Delvin, 2011).
As defined by Funk and Wagnalls New World Encyclopedia (2002), hydrogen
peroxide is a chemical compound of hydrogen and oxygen with the formula H2O2. Pure,
anhydrous hydrogen peroxide is a colorless, syrupy liquid with a sp.gr. of 1.44. It blisters
the skin and has a metallic taste. The liquid solidifies at –0.41° C (31.4° F).
Concentrated solutions are unstable, and the pure liquid may explode violently if heated
to a temperature above 100° C (302.4° F). It is soluble in water in all proportions, and
the usual commercial forms are a 3% and a 30% aqueous solution. To retard the
decomposition of the peroxide into water and oxygen, organic substances, such as
acetanilide, are added to the solutions, and they are kept in dark bottles at low
temperature. Hydrogen peroxide is manufactured in large amounts by the electrolysis of
aqueous solutions of sulfuric acid or of potassium bisulfate or ammonium bisulfate. It is
also prepared by the action of acid on other peroxides, such as those of sodium and
barium. Hydrogen peroxide acts as both an oxidizing and a reducing agent. Its oxidizing
properties are used in the bleaching of substances, such as hair, ivory, feathers, and
delicate fabrics, which would be destroyed by other agents. It is also used medicinally,
in the form of a 3% aqueous solution, as an antiseptic and throat wash. Hydrogen
peroxide is used in restoring the original colors to paintings that have darkened through
the conversion of the white lead used in the paintings to lead sulfide. The hydrogen
peroxide oxidizes the black lead sulfide to white lead sulfate. It is also used as a source
of oxygen in the fuel mixture for many rockets and torpedoes. As a reducing agent it
reacts only with such easily reduced chemicals as silver oxide and potassium
permanganate.
Journal source
In an article entitled, “The Decomposition of Hydrogen Peroxide by Blood.
George Senter’s Discovery of the Enzyme Involved” (Stock & Stuart, 2005), various
experiments were done to determine the enzyme that catalyze the oxidation of
hydrogen peroxide. Enzymes in substances that caused the decomposition of hydrogen
peroxide were provisionally termed superoxidases. Preliminary experiments on the rate
of decomposition, carried out with diluted blood, implied that the rate of reaction was of
first order with respect to the concentration of hydrogen peroxide. The research was
conducted by George Senter by the 1900s. Senter concluded that, in dilute solutions,
the rate of decomposition of hydrogen peroxide was proportional to the product of the
respective concentrations of peroxide and of Hämase (now termed catalase) (Stock &
Stuart, 2005).
Internet Source
The enzyme catalase in blood speeds up the decomposition of hydrogen
peroxide. Catalase is very efficient at decomposing hydrogen peroxide; one molecule of
the enzyme can catalyse the conversion of over 6000,000 hydrogen peroxide molecules
into water and oxygen every second. The enzyme occurs widely in tissues such as the
liver and prevents accumulation of, and tissue damage by, hydrogen peroxide that is
produced during metabolism. Catalase found in human red blood cells is a complicated
chemical consisting of four polypeptide chains with 500 amino acids in each chain. Each
peptide chain includes a porphyrin haem group. These are the active components which
allow the enzyme to catalyze the decomposition of hydrogen peroxide. Hydrogen
peroxide is a powerful oxidising agent but is unusual in that it can act as reducing agent
under certain conditions. The oxidation number of oxygen in hydrogen peroxide is -1,
intermediate between 0 in oxygen and -2 in water, and this allows the oxygen to act as
both a reductant and oxidant in either acid (H2O2) or alkali (HO2-) solution.
(www.eic.com, ret, February 2013)
Top Related