AIM OF THE STUDY: The study is aimed at identifying the key ingredients of papaya leaf extract and elucidate the mechanism (s) of action of the identified potent component in mitigating thrombocytopenia (Thp).
MATERIALS AND METHODS: C. papaya leaf juice was subjected for sequential fractionation to identify the anti-thrombocytopenic phytochemicals. In vivo, stable thrombocytopenia was induced by subcutaneous injection of 70 mg/kg cyclophosphamide (Cyp). After induction, rats were treated with 200 and 400 mg/kg body weight papaya leaf juice and with identified fractions for 14 days. Serum thrombopoietin level was estimated using ELISA. CD110/cMpl, a receptor for thrombopoietin on platelets was measured by western blotting.
RESULTS: Administration of cyclophosphamide for 6 days induced thrombocytopenia (210.4 ± 14.2 × 103 cells/μL) in rats. Treating thrombocytopenic rats with papaya leaf juice and butanol fraction for 14 days significantly increased the platelet count to 1073.50 ± 29.6 and 1189.80 ± 36.5 × 103 cells/μL, respectively. C.papaya extracts normalized the elevated bleeding and clotting time and decreased oxidative markers by increasing endogenous antioxidants. A marginal increase in the serum thrombopoietin (TPO) level was observed in Cyp treated group compared to normal and treatment groups. Low expression of CD110/cMpl receptor found in Cyp treated group was enhanced by C. papaya extracts (CPJ) and CPJ-BT. Furthermore, examination of the morphology of bone marrow megakaryocytes, histopathology of liver and kidneys revealed the ability of CPJ and fractions in mitigating Cyp-induced thrombocytopenia in rats.
CONCLUSION: C. papaya leaf juice enhances the platelet count in chemotherapy-induced thrombocytopenia by increasing the expression of CD110 receptor on the megakaryocytes. Hence, activating CD110 receptor might be a viable strategy to increase the platelet production in individuals suffering from thrombocytopenia.
METHODS: The experimental approach in the present study was based on a bioassay-guided fractionation. The crude methanol and fractionated extracts (hexane, chloroform and water) from different parts of A. scabra (leaves, rhizomes, roots and pseudo stems) were prepared prior to the cytotoxicity evaluation against human ovarian (SKOV-3) and hormone-dependent breast (MCF7) carcinoma cells. The identified cytotoxic extracts were then subjected to chemical investigations in order to identify the active ingredients. A normal human lung fibroblast cell line (MRC-5) was used to determine the specificity for cancerous cells. The cytotoxic extracts and fractions were also subjected to morphological assessment, DNA fragmentation analysis and DAPI nuclear staining.
RESULTS: The leaf (hexane and chloroform) and rhizome (chloroform) extracts showed high inhibitory effect against the tested cells. Ten fractions (LC1-LC10) were yielded after purification of the leaf chloroform extract. Fraction LC4 which showed excellent cytotoxic activity was further purified and resulted in 17 sub-fractions (VLC1-VLC17). Sub-fraction VLC9 showed excellent cytotoxicity against MCF7 and SKOV-3 cells but not toxic against normal MRC-5 cells. Meanwhile, eighteen fractions (RC1-RC18) were obtained after purification of the rhizome chloroform extract, of which fraction RC5 showed cytotoxicity against SKOV-3 cells with high selectivity index. There were marked morphological changes when observed using phase-contrast inverted microscope, DAPI nuclear staining and also DNA fragmentations in MCF7 and SKOV-3 cells after treatment with the cytotoxic extracts and fractions which were indicative of cell apoptosis. Methyl palmitate and methyl stearate were identified in the hexane leaf extract by GC-MS analysis.
CONCLUSIONS: The data obtained from the current study demonstrated that the cell death induced by cytotoxic extracts and fractions of A. scabra may be due to apoptosis induction which was characterized by apoptotic morphological changes and DNA fragmentation. The active ingredients in the leaf sub-fraction VLC9 and rhizome fraction RC5 may lead to valuable compounds that have the ability to kill cancer cells but not normal cells.