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Hadadi et al. J Cancer Metastasis Treat 2018;4:25 I http://dx.doi.org/10.20517/2394-4722.2018.22 Page 5 of 15

Water extract (mg/mL)
5 Methanol extract (mg/mL)
Ethanol extract (mg/mL)
Rutin equivalent (mg/g dry extract) 3 2
4

0 1
Leaves Skin Pulp Seed

Figure 2. Total flavonoid content in various papaya fractions. Aluminum chloride complex forming assay was used to determine the total
flavonoid content (TFC) of the extracts. Results are mean ± SD for at least 3 experiments as quercetin equivalent. The TFC in methanol
and ethanol extracts were compared to that in the water extracts. The significant differences, as marked “*”, are reported at P < 0.05

extracts contained TPC under 1 mg/g dry weight whereas the pulp extracts have very small amounts of TPC
(0.05-0.5 mg/g dry weight).

The data for the TFC content in various papaya fraction are presented in Figure 2. The seeds and leaves
extracts contained the highest amounts of TFC ranging 2-5.5 mg/g dry weight. The ethanol or methanol
extract of leaves contained more TFC (~5 mg/g dry weight) than that of water extract (~2 mg/g dry weight).
However, water extracts of seeds contained more TFC (~5.5 mg/g dry weight) than that of ethanol or
methanol extracts (~2-2.5 mg/g dry weight). The amount of TFC in pulp and skin were less than that of seeds
and leaves. In skin, higher amounts of TFC were present in the ethanol and methanol extracts (~3.2-3.5 mg/g dry
weight) than that of water extract (> 1 mg/g dry weight). The pulp contained a lower amount of TFC than
that of other fractions. The total amount of TFC in pulp ranged 1-1.5 mg/g dry weight.

The anti-oxidation capacity of papaya fractions was measured by assaying the inhibition of DPPH oxidation
and is shown in Figure 3. The seeds and leaves contained the most anti-oxidation capacity than that of
the skin and pulp fractions. The ethanol and methanol fractions of seeds and leaves contained more anti-
oxidation activity than that of water extracts. The ethanol and methanol fractions of seeds and leaves
inhibited DPPH oxidation by 75%-85% whereas the water extracts of these fractions inhibited DPPH
oxidation by 50%-70%. The skin and pulp inhibited DPPH oxidation from 25% to 35%. There was no
significant difference between water, ethanol or methanol extracts of skin or pulp.

Effect of papaya leaves, skin, pulp and seeds extract on MDA-MB-231 breast cancer cells
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This experiment was carried out to investigate effect of papaya extracts on ER/Her-2 breast cancer cell line
using MDA-MB-231. The effect of water extract from leaves, skin, pulp and seeds is shown in Figure 4A.
When the cells were treated with water extract of papaya leaves, the cells viability is reduced in a dose-
dependent manner reaching a significant reduction of 20% (P < 0.05) at 150 mg/mL. On further increasing
the concentration of extract, the cell viability was further reduced to 30% (P < 0.05). Water extract of skin
has no significant effect except at the highest concentration (250 mg/mL) where cell viability is reduced by
a marginal 10% (P < 0.05). The pulp extract has no significant effect at any concentration. The water extract
of seeds exhibited an effect similar to the water extract of the leaves causing a significant reduction in cell
viability by 20% (P < 0.05).