| Sweet potatoe residues are rich in pectin. Pectin can inhibit proliferation and metastasis of cancercells and induce their apoptosis. However, several researches proved that modification could increasethe anticancer activity of pectin. The objective of this work was to study the preparation of pH-modifiedpectin and heat-treated pectin from sweet potato residues, as well as to investgate the effect ofpH-modified pectin and heat-treated pectin on proliferation and metastasis of human colon cancer cellHT-29, human breast cancer cell Bcap-37and human hepatoma cancer cell SMMC-7721, in order toincrease the utilization of resources and value-added of processing and provide fundamental data fordeveloping new products of modified sweet potato pectins.The response surface methodology was employed to study the extraction of pectin from sweetpotato residues. On the basis of single-factor experiments, the effects of extraction temperature,extraction time, solution pH and liquid/solid ratio on yield and galacturonic acid content of pectin wereinvestigated using Boxbenken design. The determined optimum conditions were extraction temperature93°C, extraction time2.2h, solution pH value of1.7and liquid/solid ratio (v/w)30:1. Under theseconditions, the experimental extraction yield and galacturonic acid content of pectin were5.09%and70.03%(w/w), which were in good agreement with predicted values,5.08%and69.40%, respectively.These data above suggested that the predicted models were feasible in practice. The pectin extractedunder above conditions was named the unmodified sweet potato pectin.The effects of pectins of pH-modified and heat-treated conditions on proliferation of human coloncancer cell HT-29, human breast cancer cell Bcap-37and human hepatoma cancer cell SMMC-7721were investigated and then the temperature of pH-modified pectin was determined at55°C and the timeof heat-treated pectin was treated for60min. The characterizations of pH-modified and heat-treatedpectins were determined and compared to that of unmodified pectin. The results showed thatmodification increased galacturonic acid content of sweet potato pectin, whereas decreased its DE andmolecular weight significantly (P<0.05). The microstructures of modified pectins were obviouslydifferent from microstructure of natural pectin. Unmodified and modified sweet potato pectins couldinhibit the proliferation of three types of cancer cells in time-and concentration-dependent manner. Inaddition, inhibitory effect of modified sweet potato pectins on three types of cancer cells increasedsignificantly comparing to unmodified pectin (P<0.05). Furthermore, the proliferation-inhibitory effectsof modified pectins on HT-29and Bcap-37were better than that of modified pectins on SMMC-7721.When cancer cells were treated at1mg/mL of pectin for24h, the anti-proliferation rate of pH-modifiedand heat-treated pectins to HT-29increased45.32%and61.03%and that to Bcap-37increased43.31%and42.54%, respectively, compared to that of unmodified pectin. The above data suggested thatproliferation of HT-29and Bcap-37could be inhibited effectively by modified sweet potato pectins.The effects of pH-modified and heat-treated pectins on adhension, migration and uPAconcentration of HT-29and Bcap-37were determined. The results showed that effects of anti-adhension, -migration and-uPA-activity of modified sweet potato pectins on two types of cancer cells increasedsignificantly comparing to unmodified pectin (P<0.05). When HT-29and Bcap-37cells were treated at1mg/ml of pH-modified pectin for24h, compared to the effect of natural pectin, the time for cells tocompletely detach decreased7.69%and21.95%, migration rate decreased48.36%and50.45%and theuPA concentrations of cells decreased1.65%and20.36%, respectively. When HT-29and Bcap-37cellswere treated at1mg/mL of heat-treated pectin for24h, compared to the effect of natural pectin, the timefor cells to completely detach decreased6.60%and20.73%, migration rate decreased33.31%and34.46%and the concentration of uPA of cells decreased18.76%and15.67%, respectively. |
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