Enhanced production of phytotoxic polyketides isolated from Curvularia lunata by applying chemical stresses

Abstract

The secondary metabolites produced by the microorganisms have great importance in developing different medications, pesticides, and plant growth regulators. Curvularia lunata (Wakker) Boedijn, a plant pathogenic fungus, causes the leaf blight disease in Sweet basil (Ocimum basilicum L.). In the present study we have isolated and identified the fungal secondary metabolites from C. lunata and evaluated the effect of chemical stresses (NaCl, CaCl2, glycyrrhetinic acid, and NaOH) metabolites production. The influence of chemical stresses increases the production of isolated secondary metabolites. Additionally, we also check the time-dependent production of identified metabolites. The three secondary metabolites, radicinin (1), radicinol (2) and 3-epiradicinol (radicinol diastereomer) (3) were isolated from the ethyl acetate extract of C. lunata and the NMR and HR-ESI-MS spectral analysis confirmed their structure. The influence of chemical stresses increases the production of all three metabolites up to 10–30 times compared to control in all the chemical stresses except NaOH. The time-course study (12 days) showed that in the first three days, radicinin is produced. Later on, the concentration of radicinin is decreased, and the concentration of another two metabolites was increased. This is the novel finding as not reported earlier. The present study establishes a plausible biosynthetic pathway to prepare isolated fungal metabolites inside the fungal cells. The results might help the industrial production of these three polyketides (radicinin, radicinol and 3-epiradicinol) isolated from C. lunata.