Production of bioactive compounds with bactericidal and antioxidant potential by endophytic fungus Alternaria alternata AE1 isolated from Azadirachta indica A. Juss.

Abstract

For combating multidrug-resistant microorganisms, exploration of natural compounds from plant endophytes increases the chance of finding novel compounds. An efficient bioactive metabolites producing endophytic fungal strain AE1 was isolated from leaves of Azadirachta indica A. Juss. The metabolites were found to be thermostable, non-proteinacious and produced prominent zones of inhibition against numbers of Gram positive and Gram negative bacteria. Based on 28S rDNA (D1/D2) sequence homology the isolate AE1 was identified as Alternaria alternata . Malt extract broth was found effective for the maximum production of bioactive metabolites by the isolate and was subjected for solvent extraction. The Ethyl acetate (EA) fraction of AE1 showed MIC values of 300–400 μg/ml against Gram positive and Gram negative bacteria tested. The cidal mode of action of EA fraction was detected by treating bacterial cultures at mid log phase. Scanning electron microscopic study supported morphological disintegration of bacterial cells. Release of nucleic acid, protein and potassium ions (K + ) also suggested lysis of bacterial cells or leakage of cell membrane upon treatment. In addition, reduction of the activity of EMP pathway, TCA cycle and gluconeogenic enzymes in all bacteria suggested the interference of antibacterial principles with central carbohydrate metabolic pathways. Thin layer chromatographic separation followed by GC-MS analysis of EA fraction suggested numbers of antimicrobial compound production by AE1. In addition, DPPH free radical as well as superoxide radical scavenging assay also suggested strong antioxidant potential of AE1 with an IC 50 value of 38.0±1.7 μg/ml and 11.38±1.2 μg/ml respectively. On the basis of above facts it can be concluded that the strain AE1 will be a good source of bioactive compounds having medicinal importance.

Muscodor sp. IBRL OS-94, A Promising Endophytic Fungus of Ocimum sanctum with Antimicrobial Activity

“…They also confirmed that the treated cells were lost their shape and integrity followed by the ultimate cell death. Besides, Chatterjee 58 reported some deformations and prominent degradation of cell wall structures were observed on Escherichia coli, and Salmonella Typhimurium exposed to the extract of Alternaria alternata AE1, a fungal endophyte from Azadirachta indica. They also observed end-to-end joining of bacterial cells upon treatment indicating an effect of antimicrobial agents on normal cell division function and presumed that the massive distortion of morphological structures of bacteria cells may be due to the mode of action of antimicrobial agents on the bacterial cell wall.…”

Bio-Guided Fractionation of Prenylated Benzaldehyde Derivatives as Potent Antimicrobial and Antibiofilm from Ammi majus L. Fruits-Associated Aspergillus amstelodami

“…However, endophytic fungi from genus Aspergillus have been stated as a source of bioactive secondary metabolites having diverse applications [36,37,38]. Bioactive metabolites derived from endophytic fungi revealed antimicrobial activity against a variety of organisms [13,14].…”

“…Moreover, endophytic fungi are not counted as saprophytes since they are related to living tissues and may participate in the wellbeing of the plant [10]. These fungi have been identified as useful sources of bioactive secondary metabolites and many of them have the ability to produce antimicrobial substances [11,12,13,14].…”

Harnessing the Phytotherapeutic Treasure Troves of the Ancient Medicinal Plant Azadirachta indica (Neem) and Associated Endophytic Microorganisms

“…which also possesses antipathogenic activities [368]. Recently, Chatterjee et al [369] identified the metabolites produced by Alternaria alternata isolated from A. indica showing inhibitory activities against Gram-negative and Gram-positive bacteria. The highly functionalized antibacterial naphthaquinone, javanicin (15), has been reported from an endophytic fungus Chloridium sp.…”