Effect of Gamma Irradiation on Some Pharmacological Properties and Microbial Activities of Melinjo (Gnetum gnemon Linn.) Seeds

Background: Ionizing radiation, such as gamma irradiation, serves as a useful approach to inhibit spore germination and to control pathogens in postharvest seeds. Recently, its application on phytochemical sources and its influence on antioxidant activity of various phytochemical compounds has become an interesting topic to be explored. Objective: The objectives of this study were to determine the effect of gamma irradiation as sterilization method on the resveratrol content and its antioxidant, HMG-CoA reductase inhibitory and dipeptidyl peptidase-4 (DPP-4) inhibitory activities of Melinjo (Gnetum gnemon) seeds. Methods: In this research, melinjo seeds were irradiated by 0.0; 2.5; 5.0; 7.5; and 10.0 kGy with gamma irradiation and then extracted with ethanol. The extracts were tested for resveratrol content with HPLC, antioxidant activities by DPPH assay, HMG-CoA inhibitory activity using HMG-CoA reductase assay kit and DPP-4 inhibitory activity using DPP-4 Inhibitor Screening Assay Kit. Gamma irradiation has effect on resveratrol content, antioxidant activity, HMG-CoA reductase inhibition and DPP-4 inhibitory activity. Results: From the research, the highest value of resveratrol content is 0.18±0.004 mg/g seeds powder found in 5.0 kGy gamma irradiation treatment with IC50 94.64±0.236 μg/mL, while the highest HMG-CoA reductase inhibition is shown in 2.5 kGy irradiation dose. Melinjo seeds irradiated by 2.5 kGy gamma irradiation also shown a significant increase of DPP-4 inhibition activity. Conclusion: This study suggests that 2.5-5 kGy radiation is the effective gamma irradiation dose to improve the quality of melinjo seeds.