| Objectives Salt-tolerance endophytic fungi were isolated and purified from Glycyrrhizauralensis Fisch and the fermentation products containing licorice flavonoids were screened.Anti-oxidation effects were studied to screen the active fungi strains and analysis was carriedout on the secondary metabolic products of active strains. Finally, inducing regulation of plantgrowth regulator methyl jasmonate on the accumulation of Licochalcone A in fermentationbroth of fungus named10-2-G-4were investigated to lay the foundation for alternativeresources of G. uralensis.Methods Using tissue isolation method, endophytic fungi were isolated in the traditionalPDA medium and salt PDA medium under the temperature28℃and3to7days. Qualitativeanalysis of fermentation products were carried out by TLC, HPLC-UV and HPLC-FLDmethod to search for possible fungi which produce licorice flavonoids. By using DPPHradical experiment, anti-oxidation effect was investigated. HPLC-FLD method was used todetermine the licochalcone A in fermentation broth of10-2-G-4strain and the inducingregulation of methyl jasmonate under different concentrations of20,40,60,80,100μmol/Land different supplemented time of0,3,7days.Results Totally108strains of endophytic fungi, including normal group of25strains,83strains of salt tolerant group have been isolated; among them,24strains were obtained from3%group with the ratio of22.2%in the total fungi,16strains from5%group with the ratio of14.8%,20strains from8%group with the ratio of18.5%, and23strains from10%groupswith the ratio of21.3%. TLC method was applied to screen31strains possibly containingflavonoids. Among them,4strains were from3%group with the ratio of12.9%,2strainsfrom5%group with the ratio of6.5%,10strains from8%group with the ratio of32.3%, and 15strains from10%group with the ratio of48.4%.DPPH antioxidant experiment showed that the ethyl acetate layer of the fungi strains named3-6-G-3,8-2-G-3,8-4-Y-3,10-2-G-4,10-5-Y-3,10-6-J-2,3-5-Y-1,8-4-G-1,8-4-J-4,8-5-G-3,10-2-G-2,10-2-G-3, and10-5-J-1have significant anti-oxidation effect. The hypha layer ofthe fungi strains named10-2-G-3,5-5-J-4, and10-4-Y-3and n-butanol layer of fungus named8-2-G-4also have the anti-oxidation activity equal to total licorice flavonoids. The resultsshowed that more active strains were obtained under the8%, and10%salt concentrations.7strains named3-5-Y-1,8-4-G-1,8-4-Y-3,8-4-J-4,8-5-Y-2,10-2-G-3and10-6-J-2werefound to possibly produce liquiritin with3strains named3-6-G-3,8-5-G-4, and8-5-Y-2producing isoliquiritin,3strains named10-4-Y-1,10-5-J-1,10-4-Y-3producing glycyrrhizin,3strains named10-2-G-4,10-6-J-1,10-6-J-2producing licochalcone A and1strain named8-2-G-3producing echinatin.Licochalcone A was detected in the ethyl acetate and hypha layers of10-2-G-4after adding100μmol/L of methyl jasmonate at the third or seventh day of fermentation. The peak areawas the highest when adding the regulator at the third day of fermentation.Conclusions No significance was found among different salt concentrations on the quantityof isolated fungi. The activity of ethyl acetate layer was higher than hypha and n-butyl alcohol.The quantities of the fungi and active fungi were highest under8%and10%saltconcentration. It showed that the salt concentration has significant influence on thebiosynthesis of secondary metabolites and activity; therefore, more active strains wereobtained under the salt-culture condition. The plant growth regulator methyl jasmonate has acertain induction on the biosynthesis of licochalcone A. |
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