**3.5 Antioxidant activity test of** *L. plantarum* **exopolysaccharide with FRAP (ferric reducing antioxidant power) and ABTS (2,2′-azinobis (3-ethylbenzatiazoline)-6-sulfonate) methods**

The results of the exopolysaccharide antioxidant activity test using the FRAP method showed that exopolysaccharides were potential to be antioxidants based on their ability to reduce colorless Fe3+ TPTZ (2,4,6-tripyridyl-s-triazine) to blue Fe2+, so that the antioxidant power of a compound was analogous to reducing ability of the compound. Fe3+ TPTZ compounds represented oxidizing compounds that might be present in the body and could damage body cells, while samples contained antioxidants which could then reduce Fe3+ TPTZ compounds to Fe2+ TPTZ so that Fe3+ TPTZ compounds would not carry out reactions that damage body cells. The more the concentration of Fe3+ TPTZ reduced by the sample to Fe2+ TPTZ, the higher the antioxidant activity of the sample.

The reducing activity of the EPS samples was determined according to the method described by Benzie and Strain [54]. Calibration using FeSO4 which expressed as mg Fe(II) per gram extract (**Figure 5a**). The antioxidant activity test using the ABTS method using vitamin E as a comparison (**Figure 5b**), showed an IC50 of 8.3090 (μg/ ml). The value of antioxidant test results from EPS *L. plantarum* using the FRAP and ABTS methods are listed in **Table 5**.

The results of the antioxidant activity test of EPS *L. plantarum* treatment with a concentration of Se2+ 175 mmol showed the highest FRAP value, namely 0.289 ± 0.018 mg FeSO4/mg; and the best antiradical ABTS activity, namely IC50 61,882 mg/ml. Meanwhile, Zn2+ 15 mmol treatment showed the highest FRAP value, namely 0.479 ± 0.035 mg FeSO4/mg; and the best antiradical ABTS activity, namely IC50 55,535 mg/ml. The results showed that EPS *L. plantarum* had very strong antioxidant potential. The principle of the ABTS method was that EPS antiradical compounds would ward off free radicals marked by the loss of blue color (decolorization) in the ABTS reagent. It was indicated by a decrease in the absorbance value of the measured sample absorption. The advantages of ABTS compared to other methods were that the test was simple and easy to repeat; and the most important thing was that it was flexible and could be used to measure the activity of both hydrophilic and lipophilic antiradicals [55].

#### **Figure 5.**

*(a) Standard curve of FeSO4.7H2O and (b) relationship of vitamin E concentration (ppm) to % inhibition.*

### **4. Conclusions**

The production of EPS derived from the group of lactic acid bacteria including *L. plantarum* was in great demand because it was safe for consumption. The effect of EPS to improve food texture was a strategy to reduce the use of additives. The potential of EPS to be applied in the pharmaceutical field opened up opportunities for researchers to increase EPS production through modification of the fermentation medium by adding coconut water, Na-Acetate and minerals (Se2+ and Zn2+). The increase in EPS production by *L. plantarum* occurred due to the addition of natrium acetate concentration of up to 1%. Natrium acetate concentration of 0.75% gave significantly different EPS results to the control. EPS production by *L. plantarum* was optimum at 100 mmol of Se2+ concentration and 12.5 mmol of Zn2+ concentration, based on the highest ratio of glucose: protein.

The effect of Se and Zn concentrations on the antioxidant activity of EPS using the FRAP and ABTS methods shows that the higher the concentration of these trace elements, the higher the antioxidant activity.

The addition would affect the increase in enzyme activity for the synthesis of EPS. The antioxidant activity test of the *L. plantarum* EPS compound showed a very strong category.

### **Acknowledgements**

The authors are grateful to Dr. Arif Nurkanto, Head of Laboratory in Research Center for Biosystematics and Evolution, National Research and Innovation Agency (BRIN), for their valuable support to complete this study. We express our gratitude to Apt. Lisana Sidqi Aliya, S. Farm., M. Biomed., and Apt. Dr. Herdini, Lecturer at Fac. of Pharmacy-ISTN, Jakarta for suggestions during the research.

### **Conflict of interest**

The authors declare that there are no competing interests.

*Effect of Sodium Acetate and Trace Element (Se2+, Zn2+) on Exopolysaccharide Production… DOI: http://dx.doi.org/10.5772/intechopen.104547*
