3-Hydroxyanthranilic acid (3-HAA) is an intermediate in the metabolism of the amino acid tryptophan. 3-HAA is an aminobenzoic acid generated by substitution of benzoic acid at C-2 with an amine group and at C-3 by a hydroxy group. 3-Hydroxyanthranilic acid is a new antioxidant isolated from methanol extract of tempeh [1].

Tryptophan metabolism by the kynurenine pathway (KP) plays an important role in the pathogenesis of inflammatory, infectious, and degenerative diseases [2]. 3-HAA effectively suppressed glial cytokine and chemokine expression and reduced cytokine-induced neuronal death [2]. In astrocytes, 3-HAA induced the expression of hemeoxygenase-1 (HO-1), an antioxidant enzyme with anti-inflammatory and cytoprotective properties. In cultured adult human astrocytes, 3-HAA induced HO-1 expression, which has also been observed after injection to mouse brains [2]. 3-HAA acted as a co-antioxidant for α-tocopherol, inhibiting human low density lipoprotein and plasma lipid peroxidation [3]. 3-HAA inhibited nitric oxide (NO) synthase in macrophages and stimulated TGF-β production, suppressing pro-inflammatory activity of Th1 cells [1].

References:
[1] Stone T W, Stoy N, Darlington L G.  An expanding range of targets for kynurenine metabolites of tryptophan[J]. Trends in pharmacological sciences, 2013, 34(2): 136-143.
[2] Krause D, Suh H S, Tarassishin L, et al.  The tryptophan metabolite 3-hydroxyanthranilic acid plays anti-inflammatory and neuroprotective roles during inflammation: role of hemeoxygenase-1[J]. The American journal of pathology, 2011, 179(3): 1360-1372.
[3] Thomas, S. R.,Wittig, P.K. and Stocker, R. 3-Hydroxyanthranilic acid is an efficient, cell-derived co-antioxidant for α-tocopherol, inhibiting human low density lipoprotein and plasma lipid peroxidation. The Journal of Biological Chemisty 271, 2714-32721 (1996).