POMEGRANATE PEELS: A NEW SOURCE OF NUTRACEUTICALS AND BIOLOGICAL ACTIVITIES

Punica granatum L. (Punicaceae), commonly known as pomegranate, is a deciduous shrub cultivated throughout around the world and in particular in the Mediterranean area. It is consumed as a fresh fruit or processed into juice, where the rind or peel and seeds of the fruits are discarded causing the waste of the large raw materials. [1] Recently, there is an increasing interest to the pomegranate agri-wastes. Due to the high antioxidant ingredients of pomegranate peels, they are accepted as potential additives to cosmetic and food products. [2] In this communication, we report the study on Punica granatum cv. “Akko” peels to verify the possible use of these wastes as an economic value-added ingredient in formulations of nutraceutical/functional products aimed to prevent several types of diseases, especially cancer. For this reason, the aim of this study was dual. First, the isolation of β-glucans and second, the evaluation of antitumor and in vitro ROS scavenging activity of both methanol and acetone extracts from pomegranate peels. β-glucans were isolated from pomegranate peels for the first time. The extraction procedure involved: (a) alkaline treatment of flour (b) isoelectric precipitation of protein residue (c) and alcohol precipitation of β-glucans. The β-glucan content was 24 mg per gram of dry sample. The effects of peel methanol and acetone extracts on tumour cells viability were evaluated using different human cancer cell lines, namely: estrogen receptor positive (ER+) MCF-7 and triple negative (ER-, PR- and HER-2/Neu not amplified) MDA-MB-231 breast cancer cells, the human colorectal RKO cancer cells, the human uterine cervix epithelium Hela (ER-) and endometrial Ishikawa (ER+) cancer cells. Different concentrations of the extracts were used to expose cancer cells continuously for 72 hours and, at the end, cell viability was measured using the MTT assay. An impressive antitumor activity of methanol fraction was detected against HeLa and MCF-7 cells, with IC50 values of 4.45±0.3 and 5.63±0.4 μg/mL, respectively. A lesser, but still good, activity was recorded for Ishikawa cells (IC50 equal to 10.6±1.0 μg/mL). The peel acetone extract possessed, as well, a significant antitumor activity, but from two to eight time minor than the methanol fraction with respect to the same cell used in these assays. The results showed that the extracts diminish cancer cell proliferation by triggering the intrinsic (or mitochondrial) apoptotic pathway, without cytotoxic effects on the proliferation of non-tumoral human breast MCF-10a and murine 3T3-L1 fibroblasts. Moreover, their outstanding antioxidant properties have been proved by protection assays conducted on 3T3-L1 murine fibroblasts. The results indicated that pre-treatment with peel methanolic and acetone extracts was able to protect 3T3-L1 murine fibroblasts from the oxidative stress induced by menadione treatment. In conclusion, outcomes promote the use of pomegranate wastes as functional food or nutraceuticals for daily use, with a double value on both human health and environmental impact. [1] Ferrueloa, A.; Romerob, I.; Cabrerab, P.M.; Aranceb, I.; Andr e'sb, G.; Angulob, J.C. Actas Urol. Esp. 2014, 38 (6), 397˗ 404. [2] Akhtar, S.; Ismail, T.; Fraternale, D.; & Sestili, P. Food Chemistry 2015, 174, 417˗ 425.