Chen, M; Zhou, JR; Li, CY; Song, YY; Xie, LJ; Chen, S; Zeng, RS
Isolation, identification and bioactivity of allelochemicals of Streptomyces sp. strain 6803 | Allelochemicals; allelopathy; antimicrobial activity; flavonoids; identification; isolation; phenolics; phytotoxicity; Streptomyces sp. | Streptomyces spp produces numerous antibiotics to inhibit the growth of neighbouring microbial competitors, however, their potential allelopathic effects on plants is ignored. Streptomyces sp. strain 6803 was isolated from the rice soil, This strain showed allelopathic effects on both fungal pathogens and plants. Ten allelochemicals were isolated and purified from fermented broth of the strain through column chromatography. Their structure was identified on the basis on their IR, MS. H-1 and C-13 NMR. The identified Compounds are: 7,4'-dihydroxy- flavone (1), 5.7-dihydroxy -8-methoxyflavone (II), 5,7,4'-trihydroxyflavone (Apigenin, III), 5.7,4'-trihydroxy- isoflavone (Genistein, IV), diisobutyl phthalate (DiBP, V), dibutyl phthalate (DBP, VI), 4-hydroxy -benzoic acid (VII), salicylic acid (VIII), benzoic acid (IX), N-acetyl- tyramine (X). Bioassay showed that all isolated compounds had phytotoxicity. Among them the phenolic compounds (VII-IX) displayed higher phytotoxicity. Compound VIII inhibited the root growth of barnyardgrass (Echinochloa crusgalli) and rape (Brassica campestris L.) by 86.6 and 100%, respectively at 0.3 mM concentration. The flavones (I-IV) showed strong antimicrobial activity. The compounds II, III and IV at 0.3 mM inhibited the Fusarium graminearum in 25.0, 26.6 and 28.2 mm diameters, respectively. However, these flavones were less allelopathic to plants than phenolic compounds. Our results suggested that Streptomyces sp. strain 6803 uses flavone compounds for resistance to microbes and phenolic compounds for allelopathic effects on plants.