Antimicrobial activity and antioxidant capacity of fermented indigo leaves

Abstract

Naturally fermented indigo leaf extract was able to inhibit the growth of Aeromonas hydrophila with a MIC value of 781.25 µg/ml. Indigo leaf extract fermented with the bacterium isolate 7, indigo leaf extract fermented with the bacterium isolate 9 and naturally fermented indigo leaf extract can inhibit the growth of Streptococcus agalactiae with MIC values of 6,250, 1,562.5 and 3,125 µg/ ml and can also inhibit the growth of Bacillus cereus with MIC values of 1,562.5, 1,562.5 and 781.25 µg/ml, respectively. Candida albicans was inhibited by indigo leaf extract fermented with the bacterium isolate 7 and indigo leaf extract fermented with the bacterium isolate 7 with MIC values of 6,250 and 390.63 µg/ml, respectively. The inhibitory zone of B. cereus with naturally fermented indigo leaf extract at concentrations of 15, 30, 60 and 120 mg / ml was 17.3, 17.6, 18.0 and 19.1 mm whereas fermented indigo leaf extract with the bacterium isolate 9 at the same concentrations with B. cereus inhibitory zone of 16.2, 18.4, 19.3 and 22.2 mm. The inhibitory zone of A. hydrophila with naturally fermented indigo leaf extract at the 30, 60, 120 mg / ml was 8.2, 9.6 and 14.2 mm whereas indigo leaf extract fermented with the bacterium isolate 9 at the same concentrations was 9.1, 13.3 and 17.8 mm. The antioxidant properties using ABTS assay of naturally fermented indigo leaf extract was 92.83 ± 0.04 µg TE / g, and indigo leaf extract fermented with the bacterium isolate 9 was 91.58 ± 0.04 µg. TE / g. FTIR Spectra of crude extract of naturally fermented indigo leaves and indigo leaves fermented with the bacteria isolate 9 possess 4 peaks, including 33331.78, 2122.47, 1838.47 and 663.48 cm^-1 and 3332.81, 2128.80, 1636.35 and 664.11 cm^-1, respectively.