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Page 12 of 15 Hadadi et al. J Cancer Metastasis Treat 2018;4:25 I http://dx.doi.org/10.20517/2394-4722.2018.22

was reduced significantly by 50% (P < 0.05) at 200-250 mg/mL. The effect of methanol extract from leaves
and seeds is shown in Figure 8B. The data indicate that methanol extracts of the papaya leaves and seeds
fractions had no significant effect on cell viability of AU565 breast cancer cells. The effect of ethanol extract
from leaves and seeds is shown in Figure 8C. The data indicate that ethanol extracts of the papaya leaves and
seeds fractions also had no significant effect on cell viability of AU565 breast cancer cells.

DISCUSSION
The present study was carried out to investigate the effect of water, methanol, and ethanol fractions of
papaya’s leaf, skin, pulp, and seeds on breast cancer cells. We initially tested these fractions for their anti-
oxidation activity. Most the anti-oxidation activity in fruits and vegetables is due to their total polyphenolic
[40]
content . Our data indicates that seeds have the highest amount of polyphenols than that of other fractions.
The leaves also continued substantial amounts of TPC which was 1/3 to that of seeds. Other fractions have
very small amounts of TPC. In seeds the amount of TPC was similar in all three extracts but in leaves
water extract has less TPC than that methanol or ethanol. Different solvents including water, methanol and
ethanol were used during present investigation because the phenolic compounds have different chemical
[41]
characteristics and polarities and their solubility varies in polar and non-polar solvents . Polar solvents are
often used for extracting polyphenols from plant samples. Methanol is a very efficient solvent for extracting
polyphenols of lower molecular weight, whereas aqueous acetone is generally used for extraction/isolation of
[42]
higher molecular weight flavanols . Ethanol is also a good solvent for polyphenol extraction which is also
safe for human consumption. In addition, aqueous mixtures containing methanol, ethanol, ethyl acetate,
or acetone have also been used by several investigators. Currently, over 8000 phenolic structures have been
[43]
identified in fruits and vegetables , and flavonoids are one of the major phenolic class comprising of almost
[43]
4000 compounds present in different edible plants . We also determined the total flavonoids in the papaya
extracts. Our data show that water extract of seeds and methanol and ethanol extracts of leaves contained
the highest amount of TFC, which represented about 30%-40% of total phenolic compounds in seeds and
leaves. These data suggest that seeds may contain water soluble small molecular weight polyphenols whereas
leaves may contain less water-soluble high molecular weight polyphenols.

Next the anti-oxidation activities were determined in these fractions. The leaves and seeds possess the
highest anti-oxidation activities. Although leaves and seeds have different phenolic and flavonoids contents,
they have similar profile for their anti-oxidation activity. It was interesting to note that methanol and
ethanol extracts exhibited higher anti-oxidation activity than the water extract in all papaya fractions. This
difference could be due to the differences in the chemical structure of polyphenols and perhaps polyphenols
are more soluble in an aqueous mixture of methanol or ethanol than water alone.

The different extracts from various fractions of papaya were used to determine their effects in breast
cancer cells. As explained in the introduction section, breast cancer is characterized by different molecular
phenotypes. In our initial studies, not much anti-cancer activity was found in pulp and skin extracts.
These fractions were also very low in their polyphenolic contents. On the other hand, leaves and seeds
showed anti-cancer activity and these fractions have significant amounts of polyphenols. The subsequent
experiments were, therefore, performed only using leaves and seeds extracts. MDA-MB-231 was a
representative of ER/Her-2 breast cancer subtype. The water extracts of leaves and seeds were effective on
-
-
these cells. The methanol and ethanol extract showed no significant effect. MCF-7 cells line was used as
+
a representative of ER /Her-2 breast cancer. None of the extracts from seeds or leaves exhibited any effect
-
+
on these cell lines. Sk-Br-3 cells were used as a representative of ER /Her-2 breast cancer subtype. It is
clear from the data that only water extract of leaves exhibited effect on these cells line. MDA-MB-361 cell
+
+
line was used as a representative of ER /Her-2 breast cancer subtype. Again, no effect was found by any
-
of the leaves or seeds extract on these cell lines. From this data it is clear that only ER breast cancer cells
+
irrespective to their Her-2 expression were significantly affected by water extracts of leaves. Whereas ER