Abstract:
Phenazine-1-carboxylic acid (PCA), isolated from
Pseudomonas, is a very important fungicidal agent. PCA and its derivatives revealed good biological activities in the field of medicine and agrichemicals. In this paper, two series of PCA derivatives containing 1,3,4-thiadiazole and 1,3,4-oxadiazole were designed and synthesized to explore novel fungicidal candidates. Their
in vitro and
in vivo fungicidal activities were evaluated. The title compounds
I 8 (X=S, R=2-OCH
3) and
I 22 (X=O, R=2-OCH
3) had EC
50 vaues of 33.25 μg/mL and 46.52 μg/mL against
Fusarium graminearum, respectively, which were about 3-4 times better than of PCA (EC
50 = 128.54 μg/mL).
In vivo results showed that compounds
I 8 and
I 22 gave better bioactivity (inhibitory rates of 58.69% and 55.37% at 500 μg/mL, respectively) against
F. graminearum than that of PCA (25.14%). Preliminary structure-activity relationship study found that the introduction of electron-donating groups were favored to improving the activity of the derivatives, and the substitution at
ortho-position of benzene ring would be favored to fungicidal activity. The substitution position of the same substituent on the benzene ring was in the order of
o >
p >
m according to the bioactivity.These results can be used to guide the further structural modification of these compounds for novel fungicidal agent.