L-Indole-3-lactic acid

L-Indole-3-lactic acid is an L (-)-tryptophan metabolite found in strains of Bifidobacterium, Lactobacillus plantarum and Lactobacillus paraplantarum, and also an indole-based antioxidant. L-Indole-3-lactic acid is produced via the pathway that converts tryptophan into indole-3-pyruvic acid. L-Indole-3-lactic acid acts as a free radical scavenger to eliminate DPPH free radicals. L-Indole-3-lactic acid can be used in antioxidant and metabolism-related research ^{[1] [2]}.

In Vitro, L-Indole-3-lactic acid (0.05% L-tryptophan; 4 days) can be produced from L-tryptophan via 4-day incubation under anaerobic conditions using resting cells of 51 tested Bifidobacterium strains, with strain-dependent conversion rates^[1]. L-Indole-3-lactic acid is produced by B. breve B828 via the transformation of indole-3-pyruvic acid in both growing and resting cells, which validates the tryptophan metabolic cascade of tryptophan → indole-3-pyruvic acid → L-Indole-3-lactic acid^[1]. L-Indole-3-lactic acid (20 min) exhibits DPPH free radical scavenging activity, with an EC50 value of 13.4 mM^[2]. L-Indole-3-lactic acid is produced at relatively high levels by Lactobacillus plantarum strains, with Lactobacillus paraplantarum strains producing similar levels, while other lactic acid bacteria species only produce low levels of this substance^[2].

References:
[1]. Aragozzini F, et al. Indole-3-lactic acid as a tryptophan metabolite produced by Bifidobacterium spp. Appl Environ Microbiol. 1979 Sep;38(3):544-6.
[2]. Suzuki Y, et al. Identification of antioxidants produced by Lactobacillus plantarum. Bioscience, biotechnology, and biochemistry. 2013;77(6):1299-302.