Inhibition of Liver Cancer HepG2 Cell Proliferation by Enzymatically Prepared Low-molecular Citrus Pectin

Abstract

Background: Low-molecular citrus pectin (LCP) is a pectin polysaccharide with low molecular weight, low degree of crux, and no branching. It is obtained by degrading natural citrus pectin (CP) through physical, chemical and enzymatic methods. LCP has received considerable attention in recent years due to its potential applications in the medical and biological fields. Methods: In our previous study, LCP was prepared from CP by using recombinant Bacillus subtilis pectate lyase B. Monosaccharide comparative analysis revealed that the galacturonic acid content of LCP was higher than that of CP. The cell viability effect of LCP was elucidated by using HepG2 cells and the Cell Counting Kit-8 (CCK-8) assay. Terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) staining, Annexin V-FITC/PI staining, and flow cytometer propidium iodide staining were performed to detect the effects of LCP on apoptosis and cell cycle arrest in HepG2 cells. Mitochondrial membrane potential (MMP) was observed through 5,5′,6,6′-tetrachloro-1,1′,3,3′-tetraethyl-imidacarbocyanine assay. Results & discussion: The Mw of the prepared LCP was 7.6 kDa, which was significantly lower than that of CP (140 kDa). Cell viability decreased with the increase in the concentration of LCP. The half-inhibitory concentration of 1.46 ± 0.02 mg/mL was determined. Treatment with 1.6 mg/mL LCP induced the apoptosis of HepG2 cells with the inhibition rate of 83.10% ± 4.72%, and the cell cycle was arrested in the S phase. Furthermore, the MMP of HepG2 cells decreased with the increase in LCP concentration. Conclusion: The enzymatically prepared LCP could inhibit the proliferation of HepG2 cells. This study provided a partial experimental basis and reference for LCP to become a potential functional food for anti-liver cancer.