Parkinsonia praecox bark as a new source of bioactive compounds
Description
Parkinsonia praecox is used in folk medicine to treat various diseases; however, its bark's antimicrobial and antiproliferative properties have not been reported. Thus, the objectives of this study were to evaluate the antibacterial activity and cytotoxicity of methanolic extract of Parkinsonia praecox bark (PpMB) on the liver (HepG2), ovarian (SKOV-3), and cervix (HeLa) cancer cells, in addition to determining the hemotoxicity in human erythrocytes and identifying the major compounds.
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Methods: The antibacterial activity of methanolic extracts was determined using the broth microdilution method and the cytotoxic effect of the extracts was assessed on cancerous and non-cancerous cells using the crystal violet assay. The hemotoxicity of PpBM was investigated in vitro on human erythrocytes by a hemolysis assay and the identification of major compounds was performed by 1H and 13C NMR and 2D NMR experiments. Results: The methanolic extracts from the bark of Parkinsonia praecox showed minimal antibacterial properties against certain clinically important strains, however, the extracts decreased cell proliferation of some cancer cells, especially of liver cancer cells (half-maximal inhibitory concentration, IC50: 104.5 µg /mL) with a selectivity index of 1.38 and 2.04 in relation to macrophages and keratinocytes, respectively. In addition, they caused minimal hemolysis and slight alterations in the cell membrane and cell morphology of human erythrocytes, confirming the low hemotoxicity of the PpBM extract. For the first time lupenone, germanicone, 3-oxo oleanane-18-en-28-ol, and combretol were identified in P. praecox bark. Conclutions: Methanolic extracts from the bark of Parkinsonia praecox contain selective compounds against HepG2 liver cancer cells and did not show toxicity in human blood red cells. There are some compounds in the extracts such as germanicone, 3-oxo-oleanane-18-en-28-ol, combretol, and especially the triterpene lupenone, that could have potential against liver cancer, however, in vitro and in vivo studies are required to confirm the efficacy and safety of these compounds. Thus, our findings significantly contribute to the limited knowledge of the chemotaxonomy of P. praecox.