Elite Zingiber extracts as potential free radical scavengers and radioprotectors

Abstract

ABSTRACT Fresh rhizome extracts of four elite Zingiber species, viz., Zingiber kangleipakense, Zingiber montanum, Zingiber officinale, and Zingiber zerumbet, prepared in 60% aqueous ethanol/60% aqueous methanol solutions were used for assessing their comparative free radical scavenging and radioprotective properties. Various methods, such as ferric ion reducing power assay, DPPH ion scavenging assay, nitric oxide scavenging assay, metal chelating assay, thiyl/sulfur free radical reactivity assay, and hydroxyl ion scavenging assay, were employed for radical scavenging capabilities. Bio-active principles, such as total phenolic, flavonoid, and ascorbic acid contents, were also assessed. Z. officinale showed the highest TPC, TFC, and ascorbic acid content of 650 mg GAE/100 g, 889 mg QE/100 g, and 3.19 mg/100 g, respectively, as well as the greatest efficacy in ferric ion reducing and DPPH scavenging ability having lowest IC50 value of 0.22 mg/mL. Z. montanum showed the lowest IC50 value of 0.91 mg/mL in NO scavenging assay and also exhibited the highest curcumin protection in thiyl free radical scavenging assay. Z. kangleipakense showed the lowest IC50 value of 0.24 mg/mL and 0.25 mg/mL in metal ion chelating assay and hydroxyl radical assay, respectively. 60% aqueous ethanol extracts of Z. officinale and Z. kangleipakense were used for radioprotective assays both for in vitro and in vivo using plasmid pBR322 DNA and bone marrow cells of albino rats, respectively, based on their significant free radical scavenging properties. At the same concentration of 0.25 mg/mL, Z. officinale and Z. kangleipakense showed 71.50% and 56.54% protection, respectively, of DNA from exposure to 6 Gy gamma radiation. Also, Z. officinale and Z. kangleipakense exhibited 51.16% and 38.96% protection from radiation-induced chromosomal damages in rats, respectively, when exposed to 2 Gy. Reduction in the DNA open circular form as well as the chromosomal aberrations in treatments with plant extracts compared to the controls confirmed the radioprotective potentials of the extracts. The results showed that the extracts possessed potential antioxidant compounds having capacities to scavenge radiation-induced free radical species. The accessibility of the extracts in radiation countermeasures can provide immense nutraceutical potentials.