Antifungal Activity of the Extract and the Active Substances of Endophytic Nigrospora sp. from the Traditional Chinese Medicinal Plant Stephania kwangsiensis

Abstract

To exploit a new source from medical plants for finding bioactive products, endophytic fungi DBR-5 identified as Nigrospora sp., was isolated from the root tubers of the traditional Chinese medicinal plant Stephania kwangsiensis Lo. The antifungal activities of the extract from its fermentation liquids were determined. The ethyl acetate extract of DBR-5 exhibited high and broad antifungal activities against plant pathogenic fungi, and showed high toxicity to Exserohilum turcicum, Bipolaris maydis, Ceratocystis paradoxa, Alternaria oleracea and Cochliobolus miyabeanus with EC 50 values respectively at 0.01 mg/mL, 0.02 mg/mL, 0.03 mg/mL, 0.03 mg/mL and 0.04 mg/mL. By a bioassay guided fractionation, three antifungal secondary metabolites were isolated from liquid culture of DBR-5, and identified as griseofulvin, deoxybostrycin and austrocortirubin on the basis of spectroscopic analysis. In vitro antifungal assay showed that griseofulvin displayed significant inhibition against the hypha growth of tested plant pathogenic fungi with EC 50 values ranging from 0.0013 mg/mL to 0.0202 mg/mL, and showed the highest toxicity to E. turcicum and C. paradoxa with EC 50 values both at 0.0013 mg/mL. Compared with the broad spectrum fungicide carbendazim, except that the toxicity of griseofulvin to Diaporthe citri and Pestalotiopsis theae was lower, the toxicity to the other eight pathogenic fungi was much higher. The inhibitory rates of griseofulvin against spore germination of A. olerace, C. paradoxa and P. theae were 100%, 100% and 94.39% respectively, at a concentration of 0.01 mg/mL. The other two compounds deoxybostrycin and austrocortirubin exhibited only weak antifungal activities. The results indicate the potential of Nigrospora sp. DBR-5 as a source of griseofulvin and also support that griseofulvin is a natural compound with high potential bioactivity against plant pathogenic fungi.

Suppression of Blast Disease in Rice Plants using Endophytic Fungus Nigrospora sp.

“…Sepengetahuan penulis, pemanfaatan cendawan endofit Nigrospora untuk mengendalikan penyakit blas pada tanaman padi belum pernah dilakukan di Indonesia. Pengujian cendawan ini secara in vitro dalam menekan perkembangan patogen dan tanaman yang berbeda pernah dilakukan di Portugal (Landum et al 2016) dan di China (Luo et al 2017;Lu et al 2022). Meskipun penelitian tentang manfaat Nigrospora sp.…”

Two Polyketides Produced by Endophytic Penicillium citrinum DBR-9 From Medicinal Plant Stephania kwangsiensis and Their Antifungal Activity Against Plant Pathogenic Fungi

“…The inhibition of samples on mycelial growth of plant pathogenic fungi was determined according to the previous report. 14 The required concentration of samples dissolved in acetone:water (1:1 by volume) was evenly mixed with molten potato dextrose agar (PDA) medium and poured into a Petri dish (sample solution:PDA medium = 1:9, v/v, mL). The control was added to the solvent of acetone:water (1:1 by volume) instead of samples solution.…”

“…The antifungal activities of these fractions were evaluated with a growth rate method. 14 The bioactive fractions F1 (1.8 g) were combined and separated further by silica gel column chromatography, and elution was performed with a linear gradient of petroleum ether/EtOAc (95:5→90:10→85 :15→80:20→75:25→70:30), and six subfractions (SF1.1-SF1.6) of 400 mL were collected. According to the determination of antifungal activities, SF1.1 (0.29 g) and SF1.2 (0.1 g) were the bioactive subfractions.…”

“…In previous studies, S. kwangsiensis was found to be a potential source of antimicrobial active endophytic fungi, and the extract of the endophytic fungus P. citrinum DBR-9 showed excellent antifungal activity. [13][14][15] Besides, the species of Penicillium had been reported to be an important source of polyketides. 2 In this paper, the purpose was to discover excellent biocontrol agents as alternatives to synthetic chemical fungicides for the control of plant pathogenic fungi in agriculture.…”

“…Carbendazim was used as the positive control, referred to the data in our previous study. 14 b “—” means that the IC 50 values are not calculated, because the antifungal activities of the compounds toward these pathogenic fungi were too low in preliminary experiment.…”