Sugar, Pigment and Enzyme Tests of Aloe barbadensis
and St. Ives Lotion Reveal More Sugars and Pigments in Aloe Plant
(Title by Andy Taylor)
(Revised by Irfan Ahmad, revised by Patrick Pruitt)
By: Irfan Ahmad, Kara Pierce, Patrick Pruitt, and Andy
Taylor
Team PIKA
LBS 145
Tuesday 3:00-6:00 pm
Dr. Luckie
01/28/03
Abstract:
By Andy Taylor and Kara Pierce
(Revised by Irfan Ahmad, revised by Patrick Pruitt)
Is there a chemical difference between the aloe in manufactured
lotion and aloe gel obtained directly from the plant? Carbohydrate,
enzyme, and photosynthetic tests were performed on St. Ives lotion and three
different constituents of Aloe barbadensis Miller: the sap, the mucilage,
and the rind. The yellow sap is in the large pericyclic tubules above
the mucilage. The mucilage is the thick layer of clear plant tissue
just below the rind (Danhof 2000). The rind is the outer, green layer.
The sap, mucilage, and rind were expected to contain similar carbohydrates
that would be absent from the lotion. The rind was expected to contain
photosynthetic pigments not found in the sap, mucilage, or lotion. The
enzyme polyphenoloxidase (PPO) was expected to be present in the sap, mucilage,
and rind but not in the lotion.
The carbohydrate tests performed included Benedict’s,
Barfoed’s, Selivanoff’s, Bial’s, and Iodine Tests (Maleszewski, et al, 2003).
These tests indicated that: the lotion contained pyranoses; the sap contained
monosaccharide reducing sugars, ketoses and furanoses; the mucilage contained
pyranoses; and the rind contained reducing sugars and pyranoses. Paper
chromatography showed that the rind was the only solution with photosynthetic
pigments. The absorption spectrum also indicated that the rind was the
only solution with photosynthetic pigments. An enzyme test for PPO
showed that it was not present in any of the solutions. The data suggests
that aloe lotion contains a smaller variety of carbohydrates. This
leads to the inference that because lotion contains fewer carbohydrates, it
may be missing a vital healing component.
Figure 11
(a)
(b)
(c)
(d)
Figure 11: This figure shows the test for Polyphenoloxidase (PPO). Each substance,
(a) the sap, (b) the lotion, (c) the rind, and (d) the mucilage, were reacted
with catechol to see if there was PPO present. For each set of cuvettes above,
the cuvette on the right shows the substance before catechol was added and
the cuvette on the left shows the substance 10 minutes after the catechol
was added. As seen in the picture, there was no visible color change, so
the absorbance of each was taken when the catechol was initially added and
again 10 minutes later. There was no significant difference in the two absorbances
to it was concluded that there was no PPO present in any of the tested substances.
Discussion:
By Kara Pierce
(Revised by Patrick Pruitt, revised by Irfan Ahmad)
The purpose of these experiments was to determine if
a commercial aloe vera lotion was similar in components to the aloe vera sap,
the aloe vera mucilage and the aloe vera rind. We were trying to find
out if the carbohydrates, enzymes, and photosynthetic components of the rind
were also present in the sap, mucilage, and a commercial lotion. We believed
that the sap, mucilage, and rind would contain similar carbohydrates, which
would be absent from the lotion, and furthermore expected to find photosynthetic
components in the rind that were not present in the sap, mucilage, or lotion.
Finally, we predicted that PPO would be present in the sap, mucilage, and
rind, but not in the lotion, due to the dilution of the lotion by other compounds
to create the commercial product.
The sap was the liquid drained from the center of the
plant when broken open. It had a distinct yellow color. The mucilage
was the thick layer of plant tissue surrounding the sap, and it was for the
most part clear. The rind was the outer layer, left behind when the
mucilage was scraped away, and was green. The lotion was a commercially
purchased product, and was white.
To find the carbohydrates, a series of simple tests were
performed. In Barfoed's test, the rind, lotion and mucilage solutions did
not show a color change from their green, white and clear colors, respectively,
indicating an absence of monosaccharides. The sap solution, however,
did show a red color change, a sign of the presence of monosaccharides.
Similar results were obtained from the Benedict's test, in which the rind,
lotion, and mucilage solutions did not show a color change, indicative of
a lack of reducing sugars. The sap solution did change to a dark reddish
color, showing that reducing sugars were present in this solution. During
the Selivanoff’s test, the lotion solution showed no distinct color change
after 120 seconds, leading us to believe it did not contain ketoses. The
sap solution did show a notable color change after 60 seconds, indicating
the presence of ketoses. Previous research suggests that the ketose
fructose may have caused this reaction to occur (Paez et al, 2000).
The rind and mucilage solutions showed very mild color change after 120 seconds,
causing us to think they did not contain ketoses, because solutions containing
ketoses typically show a color change within the first minute of being boiled.
The fourth test we did was the Bial’s test. The lotion, mucilage, and
rind solutions showed no color change, suggesting that any carbohydrates present
in the solutions were pyranoses. The sap solution underwent a green
color change, indicating the presence of pentose-furanose rings in the sap.
The next test that was performed was the Iodine test. The lack of color change
in the lotion, mucilage, and rind solutions indicated the absence of starch,
while the color change in the sap solution suggested the presence of starch
in the sap. As expected, the sap indicated the presence of reducing
sugars and monosaccharides. However, the expected reducing sugars were
not found in the rind, as it tested negatively on the Benedict’s and Barfoed’s
tests. Previous research indicated that sugars glucose, fructose, galactose,
and arabinose would be present (Paez et al, 2000), and other research also
adds that the reducing sugar mannose should be present (Pugh et al, 2001),
but these were not found in our examination of the rind. In addition,
the mucilage and lotion solutions tested negatively for reducing sugars and
monosaccharides, counter to our predictions. From these results we
can conclude that the sap also contains reducing sugars not found in the
lotion, rind, or mucilage.
An attempt was made to extract pigment from sap, mucilage,
rind, and lotion. Using paper chromatography, it was found that the
lotion, sap, and mucilage had no noticeable pigment. The rind had a small
green band, showing that it contains chlorophyll, and a faint yellow band
as well, signaling xanthophyll. This supports our prediction of pigments
exclusively in the rind. The absorption spectrum of the lotion was steadily
high. Slightly lower was the spectrum of the rind, which dipped during
the green band of the spectrum. Lower still was the spectrum of the
sap, which reflected the most light in the yellow band of the spectrum.
Finally, the mucilage had the lowest spectrum, as it did not absorb much light.
This data supports our hypothesis, in that the chromatography suggests that
the rind is the only one of the subjects containing the pigment chlorophyll,
which is necessary for photosynthesis. Also, the fact that the rind
had a high absorption spectrum shows that it is capable of absorbing plenty
of light to use in photosynthetic processes. We believe the high absorption
spectrum of the lotion is due to its thickness, rather than being an indication
of its readiness to perform photosynthesis.
Lastly, two tests were performed to determine the presence
of PPO, finding that the enzyme PPO was not present in any of the solutions.
This was contrary to original predictions, which held that the enzyme would
be present in all solutions except the lotion.
Overall, these tests have found differences between the
commercial lotion and the aloe vera sap, mucilage, and rind. They have
found differences in carbohydrates and photosynthetic components, of which,
the manufactured lotion should contain to fully function as the aloe vera
gel would. Research suggests that the carbohydrates in aloe vera play
a role in the clinical usefulness of the plant, in that they aid in reducing
inflammation (Joshi, 1998). Also, research on aloe vera suggests that
enzymes present in aloe vera also play an important role in the healing abilities
of the plant (Vasquez et al, 1996). This would indicate that using the
lotion would not reap the user the benefits of the carbohydrates present in
the sap, but not present in the lotion. However, a similarity in the
components of the commercial aloe vera product to the aloe vera plant can
be noted (Ross et al, 1997).
A problem that we encountered during our research was
that while mixing the lotion solutions, the lotion did not mix well with the
distilled water, perhaps due to the possible presence of oil in the lotion.
Regardless, this resulted in a poorly formed solution, which may have affected
the results of some of the tests. Another problem was the change in
chromatography paper. One type of paper produced strong results during
previously performed structured labs. However, this paper was replaced
with a different kind in the lab, which produced weak results on the chromatography
tests. If these errors were improved upon, we believe that there would
be more noticeable differences between the Aloe barbadensis plant and the
St. Ives lotion.
