Herbicidal Characteristics and Structural Identification of the Potential Active Compounds from Streptomyces sp. KRA17-580

Abstract

Weeds are notorious plant species exhibiting a harmful impact on crops. Biological weed control is an efficient and environmentally friendly technique, usually constitutes naturally derived compounds, including bioherbicidal metabolites produced by Streptomyces sp. The isolation and structural identification of phytotoxic compounds from Streptomyces have recently been proposed as an effective way to the discovery of novel bioherbicides. In the screening of bioherbicidal agents, isolated Streptomyces strain KRA17-580 demonstrated significant phytotoxic activity against Digitaria ciliaris. Phylogenetic analysis of the 16S rRNA sequence indicated that isolated KRA17-580 is similar to Streptomyces olivochromogenes. The bacterial culture conditions were optimized for temperature, agitation, and initial pH. Streptomyces strain KRA17-580 showed intense phytotoxic activity and high cell mass at an initial pH of 5.5–7.0, more than 150 rpm, and 25–30 °C. The herbicidal compounds isolated from the culture filtrate of strain KRA17-580 were purified by solvent partition, C18, Sephadex LH20 column chromatography, and high-performance liquid chromatography. By 1D-NMR, 2D-NMR, and electrospray ionization mass spectrometry analysis, the 580-H1 and 580-H2 compounds were identified as a cinnoline-4-carboxamide (M W, 173.0490; C9H7N3O2) and cinnoline-4-carboxylic acid (M W, 174.0503; C9H6N2O2), respectively. Only these two herbicidal compounds showed strong phytotoxic activity against D. ciliaris in foliar applications. However, compound 580-H2 was more phytotoxic than 580-H1 and the toxicity was dose-dependent. The herbicidal metabolite KRA17-580 produced by Streptomyces sp. is a new bioherbicidal candidate that may provide a new lead molecule for more efficient phytotoxic compounds.

Recently Discovered Secondary Metabolites from Streptomyces Species

“…In total, eleven polyaromatic compounds were isolated from six Streptomyces species in 2020. Through herbicidal bioassay screenings, Kim et al identified strong activity associated with Streptomyces strain KRA17-580 against the weed Digitaria ciliaris [29]. Two compounds were spectroscopically characterised, a cinnoline-4-carboxamide, 580-H1 (38), and a cinnoline-4-carboxylic acid, 580-H2 (39, Figure 13).…”

“…Two compounds were spectroscopically characterised, a cinnoline-4-carboxamide, 580-H1 ( 38), and a cinnoline-4-carboxylic acid, 580-H2 (39, Figure 13). In further phytotoxicity bioassays, the carboxamide proved to be less potent than the carboxylic acid, and electrolyte leakage assays were used to verify that the observed herbicidal activity was caused by destruction of the cell membrane [29]. 39), (2S,2′′S)-6-lavandulyl-7,4′-dimethoxy-5,2′-dihydroxylflavanone ( 40), (2S,2′′S)-6-lavandulyl-5,7,2′,4′-tetrahydroxylflavanone (41), and (2′′S)-5′-lavandulyl-2′-methoxy-2,4,4′,6′-tetrahydroxylchalcone (42) [29,30].…”

“…In further phytotoxicity bioassays, the carboxamide proved to be less potent than the carboxylic acid, and electrolyte leakage assays were used to verify that the observed herbicidal activity was caused by destruction of the cell membrane [29]. 39), (2S,2′′S)-6-lavandulyl-7,4′-dimethoxy-5,2′-dihydroxylflavanone ( 40), (2S,2′′S)-6-lavandulyl-5,7,2′,4′-tetrahydroxylflavanone (41), and (2′′S)-5′-lavandulyl-2′-methoxy-2,4,4′,6′-tetrahydroxylchalcone (42) [29,30].…”

“…Figure13. The structure of 580-H1(38), 580-H2(39), (2S,2′′S)-6-lavandulyl-7,4′-dimethoxy-5,2′-dihydroxylflavanone(40), (2S,2′′S)-6-lavandulyl-5,7,2′,4′-tetrahydroxylflavanone(41), and (2′′S)-5′-lavandulyl-2′-methoxy-2,4,4′,6′-tetrahydroxylchalcone(42) [29,30].Flavonoids possess a generic structure in which two aromatic rings (A and B) are connected by a heterocyclic pyran. Investigations into bacterial endophytes of the sea sponge Halichondria panicea led to the discovery of Streptomyces sp.…”

Phytotoxic Azaphilones From the Mangrove-Derived Fungus Penicillium sclerotiorum HY5

“…It is estimated that the production loss caused by weeds is approximately 34% of the crop yield worldwide (Harding and Raizada, 2015 ; Shi et al, 2020 ). In the present situation, control weeds in farmland on a global scale are mainly dependent on chemical treatments (Travaini et al, 2016 ; Vurro et al, 2018 ); however, there are many long-term problems with the intensive application of agrochemical herbicides, such as environmental pollution, pesticide residue accumulation, and the emergence of weed resistance, which increase the difficulty of weeds control management (Kim et al, 2020 ; Shi et al, 2020 ). With the continuous discoveries of a great number of biocontrol microbial resources, exploration of microbes with excellent biological activity from extreme conditions such as marine-derived microorganisms, in recent years, have attracted much attention of scientists (Shen et al, 2020 ).…”