Effect of UV-C irradiation on the antioxidant activities of shoot cultures of Moringa oleifeira Lam. was investigated. Total phenolic and flavonoid contents and the antioxidant bioactive components were determined. The shoots of M. oleifeira were cultured for 6 weeks on Murashige and Skoog (MS) mediums containing 0.5 mg/L 6- benzyladenine (BA) for multiple shoot formation. Multiple shoots were treated with UV-C irradiation for 0 min (for the control group) 5, 10 and 15 min (for the experimental groups). After 4 weeks of culture, the shoots were extracted with methanol and analyzed for antioxidant activities using 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging, 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) scavenging and ferric reducing power (FRP) assay and the total phenolic and flavonoid contents were determined. Quantitative analysis of active compounds was accomplished by high performance liquid chromatography (HPLC). The results indicate that the shoots treated with UV-C irradiation for 10 min exhibited the highest antioxidant activities at IC50 of 31.43 mg/mL using DPPH scavenging assay, 58.98 mg TEAC/100 g fresh weight (FW) using ABTS scavenging assay and 33.78 mM FeSO4 /100 g FW using FRP assay. The total phenolic and flavonoid contents were 112.56 mg GAE/ 100 g FW and 65.31 mg QE/100 g FW, respectively. Crypto-chlorogenic acid, isoquercetin and astragalin were the highest antioxidant bioactive components with values of 30.10, 61.21 and 12.67 ng/mL, respectively. UV-C irradiation can stimulate the antioxidant capacities of M. oleifera shoot cultures. Our study will provide useful knowledge and can be utilized for improving the quality of M. oleifera raw materials in herbal supplementary food and medical uses.
Key words: Moringa oleifeira Lam., antioxidant activities, UV-C irradition, plant tissue culture.
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