Abstract
The aims of this study are to investigate the selective cytotoxic activity of supercritical carbon dioxide (scCO2)-extracted freeze-dried leaf juice (FDLJ) of Carica papaya on squamous cell carcinoma (SCC25) cells, and to delineate the best small scale extraction parameters allowing maximal extract activity. Using scCO2 as a solvent, six operating parameters were studied and the supercritical fluid extraction (SFE) process investigated using a factorial design 26-2. The processing values promoting cytotoxic activity towards SCC-25 are: high pressure (250 bar), low temperature (35 °C), extended processing time (180 minutes), as well as a large amount of starting material (5 g). The factorial experimental design successfully identified the key parameters controlling the SFE of molecules cytotoxic to SCC cells from C. papaya juice. This study also validated the extraction method and showed that the SFE yield was reproducible. The chromatographic and mass spectrometric profiles of the scCO2 extract acquired with high-resolution quadrupole time-of-flight mass spectrometry (LC-QToF-MS) were used to tentatively identify the bioactive compounds using comparative analysis. The principal compounds were likely to be mainly vitamins and phytosterols, some of which are documented to be cytotoxic to cancer cells.
Highlights
In the context of increasing demand for natural products, more effective and selective extraction methodologies are required for the rapid recovery of pharmacologically active compounds from raw plant materials[1]
The freeze-dried leaf juice (FDLJ) of tropical plant C. papaya found in Australia is subjected to a supercritical fluid extraction (SFE) method employing carbon dioxide as a solvent according to a Fractional Factorial Designs (FFDs) model of experimentation
Dulbecco’s Modified Eagle’s Medium (DMEM), DMEM-F12, penicillin/streptomycin, trypsin, and foetal bovine serum (FBS) were purchased from Invitrogen (Life Technologies, Mulgrave, VIC, Australia). 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), dimethyl sulfoxide (DMSO), analytical grade ethanol, and HPLC grade methanol were obtained from Merck (Darmstadt, Germany)
Summary
In the context of increasing demand for natural products, more effective and selective extraction methodologies are required for the rapid recovery of pharmacologically active compounds from raw plant materials[1]. Should FFD-based screening raise questions about certain factors, further investigations can be made adding to existing data and working towards full factorial information on those specific factors, that is sequential experimentation Another advantage of fractional screening is that there are fewer experiments conducted, thereby significantly reducing the time required to acquire information and lowering running costs for materials[6]. The FDLJ of tropical plant C. papaya found in Australia is subjected to a SFE method employing carbon dioxide as a solvent according to a FFD model of experimentation. This plant is well-known within tropical and sub-tropical regions. We further aimed to carry out preliminary identification bioactive compounds by LC-QToF-MS
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