Abstract
A Streptomyces isolate having antifungal activity against Pyricularia oryzae, the causal agent of rice blast disease, was isolated from soil collected in rice fields of Tanjung Karang Selangor, peninsula Malaysia.The aim of the study was to determine the antifungal activity of Streptomyces sp. isolate UPMRS4 extracts against P. oryzae and to identify bioactive antifungal compounds produced by UPMRS4. Various solvents were used for extraction of antifungal compounds and well diffusion method was used to determine the antifungal activity of the extracts. The ethyl acetate extract demonstrated the highest activity against mycelial growth of P. oryzae, with an effective inhibitory concentration (EIC) of 1.562 μg/ml significantly higher compared to that of chloroform, diethyl ether, methanol, acetone, ethanol and water. Based on GC-MS and LC-MS/MSanalyses,compounds with antifungal activity were detected such as (Pyrrolo[1,2-a] pyrazine-1,4-dione, hexahydro-3-(2-methylpropyl); Pyrrolo[1,2-a] pyrazine-1,4-dione, hexahydro-3-(phenylmethyl); ergotamine; amicomacin; fungichromin; rapamycin and N-Acetyl-D, L-phenylalanine. These compounds had good general antifungal activity and might have potential future agricultural applications.
Highlights
Rice (Oryza sativa L.) is among the most important crops all over the world and it is consumed as a staple as well as primary source of energy and protein
Metabolites can be extracted using different solvents and elucidation of the active metabolites and their structures can be performed by various methods such as gas chromatography-mass spectrometry (GC-MS), liquid chromatography-mass spectrometry (LC-MS) and nuclear magnetic resonance (NMR) [6]
Sabaratnam and Traquair [16] have indicated that Streptomyces sp. isolate Di-944 shows the same effectiveness as the fungicide, oxine benzoate, when it is used as drenching to control Rhizoctonia damping-off of tomato
Summary
Rice (Oryza sativa L.) is among the most important crops all over the world and it is consumed as a staple as well as primary source of energy and protein. Microorganisms including actinomycetes are responsible for the production of approximately 23,000 bioactive secondary metabolites that in turn produce more than 10,000 of these compounds, making up 45% of all bioactive microbial metabolites that have been identified. The efficiency of separation and identification of compounds from complex biological mixtures is very high for GC-MS [9]. This method is mainly utilized for producing fingerprints of volatile compounds which make the process of analysis repetitive [10] [11]. LC-MS is another method through which liquid chromatography is used together with mass spectrometry [9] It can identify and analyze a large number of compounds, present in small quantities whose molecular mass varies from 10 to 300,000 with different chemical properties
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