Phenazine-1-carboxylic acid mediated anti-oomycete activity of the endophytic Alcaligenes sp. EIL-2 against Phytophthora meadii.

The oomycete pathogen, Phytophthora meadii, causes various diseases in Hevea brasiliensis at different stages of its life cycle. The study reports the structural characterization of the active principle from the culture filtrate of Alcaligenes sp. EIL-2 (GenBank ID: HQ641257) offering antagonistic activity against P. meadii. Gas Chromatography Mass Spectroscopy (GC-MS) analysis showed the similarity of the compound with phenazine derivatives. The specific representations of FT-IR spectrum such as 3200 cm(-1) (OH stretching, NH stretching and presence of aromatic ring), 1737 cm(-1) (carboxylic acid), 2200-2400 cm(-1) (conjugated dienes) and 1467 cm(-1), and 1422 cm(-1) (CN bonds) were an indicative of phenazine-1-carboxylic acid (PCA). The structure of the compound was further confirmed by (1)H NMR/(13)C NMR spectroscopy, DEPT experiments, and two-dimensional NMR spectral studies, including (1)H-(1)H COSY and (1)H-(13)C HSQC as PCA with the molecular formula of C₁₃H₈N₂O₂. P. meadii was sensitive to purified PCA extract from the endophyte and a concentration of 5 μg/ml completely inhibited the mycelia growth. PCA also showed zoosporicidal activity against P. meadii zoospores. This is the first study of this kind where PCA from an endophyte of H. brasiliensis is being confirmed to carry antagonistic activity against P. meadii.
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