Optimization of Pectin Extraction from Orange Peels and Its Anti-proliferative Potential on HEp2 Cancer Cells

Worldwide, orange is one of the most widely used products in the food industry. Waste recycling of these industries could be a good source as raw material for pectin extraction. The latter has largely demonstrated its potential use in various fields, in particular pharmaceuticals. Its bioactive capacity encourages the development of various transformation processes to increase the bioavailability of pectic oligosaccharides and increase their effectiveness. In the present study, we were particularly interested in the valorization of an agricultural by-product commonly available in Algeria, orange peels, to extract pectin and study its anti-proliferative effect on cancerous cells. The extraction procedure of pectin using different protocols and several modifying parameters was investigated. Pectin was extracted by acid hydrolysis from the orange peels after removal of essential oil by hydrodistillation. Protocols for modifying pectin (chemical by pH and physical by gamma irradiation) were developed. Physicochemical characterization of different forms of pectin was carried out by determining esterification degree by Fourier transform infrared spectrometry (FTIR) and solubility of pectin in water. The anti-proliferative effect of pectin on laryngeal cancer cells (HEp2) was demonstrated in vitro by cytotoxicity test of sulforhodamine B (SRB). Induced cell death was observed by fluorescence microscopy after staining cells with Acridine Orange (AO). The obtained results show that the highest pro-apoptotic activity on HEp2 cells was observed after a 72 h contact time of orange modified and irradiated pectin. The mortality rate of cancerous cells reached 95% with an IC50 of 3.18 mg/ml compared to healthy cells which have shown a lower mortality rate.