Antioxidant Activity Enhancement Effect of Silver-Ionized Water: Silver Cation Prepared by Electrolysis

Abstract

In the present study, tap water, alkaline electrolyzed water (AlEW) and tourmaline water (TMW) were used as the electrolytes to generated the silver-ionized water (SIW), AlEW-SIW and TMW-SIW, respectively. The antioxidant properties of the samples containing ascorbic acid (AsA) were investigated by WST-kit method. The results showed that the SOD activity of AsA (2 mmol/L) dissolved in SIW (66.0%) was enhanced by about 8% compared to that of the tap water (57.9%). The SOD activity of the AlEW-SIW solution (77.3%), which was higher than that of the SIW solution, and lower than that of the AlEW solution (83.6%). The SOD activity of the TMW-SIW solution (83.0%) was similar to that of the TMW solution (82.5%). Furthermore, to classify the sample solutions, discriminant analyses were performed based on near infrared (NIR) spectral data, which was consistent with the results of the WST-kit method. The SOD activity of the AlEW-SIW and TMW-SIW solutions decreased slowly with storage time, and their SOD activities were higher than that of AlEW, TMW and the tap water solutions at storage time of 14 days. In summary, AlEW-SIW and TMW-SIW showed similar antioxidant activity enhancement as AlEW and TMW, and they also maintained the stability of the antioxidant activity of AsA during storage.

Keywords: alkaline electrolyzed water; antioxidant activity; near infrared (NIR) spectroscopy; silver-ionized water; tourmaline water.

Figure 1

SOD activity of SIW solution with different concentrations. SIW-x mA, the electrolytic current of x mA for silver-ionized water (x = 2, 4, 6, 8). All sample solutions in this study contained 2 mmol/L AsA. Different letters indicate significant difference (p < 0.05). Each value is expressed as the mean value ± standard deviation of three replicates.

Figure 2

SOD activity of SIW compound solution; (a), The 200 ppb SIW compounded with different volume fraction of 8A-AlEW; (b), The 200 ppb SIW compounded in a 1:1 ratio with AlEW generated at different electrolytic currents; (c), The 200 ppb SIW compounded in a 1:1 ratio with TMW generated at different tourmaline stone treatment temperature. TW, tap water; Ag+6 A/T25, silver-ionized water is compounded with AlEW generated at an electrolytic current of 6 A or TMW generated at a tourmaline stone treatment temperature of 25 °C. Different letters indicate a significant difference (p < 0.05). Each value is expressed as the mean value ± standard deviation of three replicates. All sample solutions in this study contained 2 mmol/L AsA.

Figure 2

SOD activity of SIW compound solution; (a), The 200 ppb SIW compounded with different volume fraction of 8A-AlEW; (b), The 200 ppb SIW compounded in a 1:1 ratio with AlEW generated at different electrolytic currents; (c), The 200 ppb SIW compounded in a 1:1 ratio with TMW generated at different tourmaline stone treatment temperature. TW, tap water; Ag+6 A/T25, silver-ionized water is compounded with AlEW generated at an electrolytic current of 6 A or TMW generated at a tourmaline stone treatment temperature of 25 °C. Different letters indicate a significant difference (p < 0.05). Each value is expressed as the mean value ± standard deviation of three replicates. All sample solutions in this study contained 2 mmol/L AsA.

Figure 3

SOD activity of AlEW-SIW (a) and TMW-SIW (b) solutions. AlEW-SIW and TMW-SIW represent the silver-ionized water produced by using AlEW generated at an electrolytic current of 8 A or TMW generated at a tourmaline stone treatment temperature of 75 °C as the electrolyte, respectively. AlEW/TMW-SIW-x mA means the electrolytic current of x mA for silver-ionized water (x = 2, 4, 6, 8). NaCl solution and tap water were used as controls. Different letters indicate a significant difference (p < 0.05). Each value is expressed as the mean value ± standard deviation of three replicates. All sample solutions in this study contained 2 mmol/L AsA.

Figure 3

SOD activity of AlEW-SIW (a) and TMW-SIW (b) solutions. AlEW-SIW and TMW-SIW represent the silver-ionized water produced by using AlEW generated at an electrolytic current of 8 A or TMW generated at a tourmaline stone treatment temperature of 75 °C as the electrolyte, respectively. AlEW/TMW-SIW-x mA means the electrolytic current of x mA for silver-ionized water (x = 2, 4, 6, 8). NaCl solution and tap water were used as controls. Different letters indicate a significant difference (p < 0.05). Each value is expressed as the mean value ± standard deviation of three replicates. All sample solutions in this study contained 2 mmol/L AsA.

Figure 4

The effect of storage time on the antioxidant activity of each sample solution. AlEW, alkaline electrolyzed water; TMW, tourmaline water; AlEW/TMW-SIW-4mA, silver-ionized water produced by using AlEW or TMW as electrolyte at 4 mA; Tap water was used as control. Each value is expressed as the mean value ± standard deviation of three replicates. All sample solutions in this study contained 2 mmol/L AsA.

Figure 5

The NIR spectra of 5 types of sample solutions at 0 h–14 days. (a), original spectra; (b), second derivative spectra used for discriminant analysis. Different color lines indicate each NIR spectra of different sample solutions.

Figure 6

Score plots of discriminant analysis. (a,b), discriminant score plots for the five sample solutions at 0 h and 14 d of storage, respectively. (c–e), discriminant score plots for tap water, TMW-SIE and AlEW-SIW solutions during storage (0 h–14 d), respectively. AlEW, alkaline electrolyzed water; TMW, tourmaline water; AlEW/TMW-SIW-4mA, silver-ionized water produced by using AlEW or TMW as electrolyte at 4 mA. All sample solutions in this study contained 2 mmol/L AsA.

Figure 6

Score plots of discriminant analysis. (a,b), discriminant score plots for the five sample solutions at 0 h and 14 d of storage, respectively. (c–e), discriminant score plots for tap water, TMW-SIE and AlEW-SIW solutions during storage (0 h–14 d), respectively. AlEW, alkaline electrolyzed water; TMW, tourmaline water; AlEW/TMW-SIW-4mA, silver-ionized water produced by using AlEW or TMW as electrolyte at 4 mA. All sample solutions in this study contained 2 mmol/L AsA.

Figure 6

Score plots of discriminant analysis. (a,b), discriminant score plots for the five sample solutions at 0 h and 14 d of storage, respectively. (c–e), discriminant score plots for tap water, TMW-SIE and AlEW-SIW solutions during storage (0 h–14 d), respectively. AlEW, alkaline electrolyzed water; TMW, tourmaline water; AlEW/TMW-SIW-4mA, silver-ionized water produced by using AlEW or TMW as electrolyte at 4 mA. All sample solutions in this study contained 2 mmol/L AsA.