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Alotaibi et al. Papaya seeds effect prostate cancer

flavus, Candida albicans and Penicillium citrinium. [30] In addition to various biological activities described
Furthermore, treatment of methanolic extract of the above, anticancer activities have been demonstrated
[21]
papaya seeds in rats induced gastroprotection without by papaya extracts in a number of in vitro studies.
signs of toxicity. This effect seems to involve sulfhydryl Papaya juice and pure lycopene, a component present
in papaya, caused cell death in the liver cancer cell line,
compounds, increased mucus, and reduced gastric Hep G2, with the half maximal inhibitory concentration
acidity. [31] (IC 50) of 20 µg/mL and 22.8 µg/mL, respectively.
[22]
Papaya seed extract also exhibited anticancer activity
in acute promyelotic leukemia HL-60 cells at IC 50 of
20 µg/mL whereas papaya pulp extract did not have
any effect even at a concentration of 100 µg/mL. In
[23]
contrast, Garcia-Solis et al. observed that papaya
[32]
pulp inhibited of proliferation of MCF-7 cells after 72-h
treatment. In our studies, we have observed almost
50% growth inhibition at 25 µg/mL of methanol seeds
extract on PC-3 cells. These results are in the similar
range of concentration as shown by other studies. [22,23]
This effect does not appear to be due to residual
methanol contamination because the methanolic
seeds extract after dryness under nitrogen gas was
subjected to freeze drying under vacuum over night to
ensure complete removal of methanol. Furthermore,
from both seeds extracts only methanolic white seeds
extract has a small (15% inhibition) effect (P < 0.05) on
3T3L1 fibroblasts [Figure 3], again suggesting unlikely
effect of methanol in the extracts.

The effect of papaya on cancer growth inhibition
are further evident from studies performed
by Morimoto et al. who patented the extracts
[33]
of different parts of papaya for the prevention,
treatment, or improvement of many types of cancer,
including stomach, lung, pancreatic, colon, liver,
ovarian, neuroblastoma, lymphoma, leukemia, and
other blood cancers. Effect of papaya leaves have

Figure 3: The effect of Papaya seeds extract on non-cancerous Figure 4: Total phenolic contents in black and white papaya seeds.
undifferentiated 3T3L1 fibroblasts. Cells (10,000/well) were The phenolic contents in black and white extracts were determined
incubated with different concentration of water (A), methanol using a Folin Ciocalteu reagent (Sigma Chem. Co., St. Louis, MO)
(B), and hexane (C) extracts of papaya white or black seeds in a and the total phenolic content was calculated from a calibration
o
CO 2 incubator at 37 C for 24 h. After treatment, cell viability was curve using Gallic acid as a standard, and the result are expressed
determined using a WST-1 assay. Results are expressed as mean as mg Gallic acid equivalent per g dry weight of sample. *Significant
± SD for at least 3 replicates. *Significant differences between differences between black seeds and white seeds were reported as
treated and untreated groups were reported as *P < 0.05 *P < 0.05
Journal of Cancer Metastasis and Treatment ¦ Volume 3 ¦ August 28, 2017 165