Radioprotective effect and antioxidant activities of Thai Gac fruit (Momordica cochinchinensis Spreng)

Abstract

Background: Radiation therapy or radiotherapy has been used to treat cancer which often causes significant adverse effects due to its cytotoxicity on both cancer and nearby intact cells. In addition, ionizing radiation generates free radicals which can damage cellular component leading to DNA damage and cell death. All cells and tissues have variable sensitivity and response to radiation injury. An antioxidant, a stable molecule, which can donate an electron to neutralize free radical. It delays or inhibits cellular damage mainly through its free radical scavenging property. Recently, there has been increasing interest in the prevention of disease mediated by free radicals. Gac fruit (Momordica cochinchinensis Spreng) is a major source of β-carotene and lycopene which can be found mainly in the red seed membrane. Both are well known antioxidant agents that can resist the negative effects of free radicals.

Objectives: The objective of this study was to determine the radioprotective effect, total phenolic content and antioxidant properties from various parts of Thai Gac fruit extracts.

Materials and methods: Each part of Thai Gac fruit including peel, pulp, aril, and seed were separately extracted using different solvents, 95% ethanol and ethyl acetate, for extraction. The total phenolic content and antioxidant activities were examined using DPPH radical scavenging assay and lipid peroxidation inhibition assay. Radioprotective effect of the extracts was evaluated by Dicentric Chromosome (DC) assay on TK6 lymphoblast cells after gamma irradiation.

Results: The ethanolic extraction of peel (EtP) showed the highest total phenolic content (140.43±0.63 mg GAE/gm), along with significant antioxidant activity which the values of SC50 were 3.72±0.12 mg/ml and 2.57±0.36 mg/ml for DPPH scavenging and lipid peroxidation inhibition, respectively. However, EtP and the ethyl acetate extract of pulp (EACN) exhibited higher LC50 values when compared to LC50 values of L-ascorbic acid (SC50=0.25±0.04 mg/ml) and α-tocopherol (LC50=0.85±0.14 mg/ml) as standard reagents. Cytotoxicity of Thai Gac fruit was studied on TK6 cells which revealed non-toxic at the concentrations up to 100 μg/ml and 25 μg/ml for EtP and EACN, respectively. Moreover, the DC assay showed that EtP exhibited radioprotective effect in a dose-dependent manner while EACN could reduce radiation-induced chromosomal abnormalities in TK6 lymphoblast cells.

Conclusion: The ethanolic extract of peel (EtP) exhibited the highest level of antioxidant activities and radioprotective effect when compared to those of other solvent extractions, suggesting it might be used as a potential natural radioprotective agent. It was found that EtP could reduce the damage caused by radiation. Our findings suggested that the peel of Thai Gac fruit extracted by 95% ethanol exhibited a potent antioxidant activity and radioprotective effects in cell line.