ABSTRACT
Some studies focused on metabolic relationships between plants and their endophytic bacterial associates, and more research is required to generate critical evidence for these relationships. In the current interest, we tried to confirm the relationship between the traditional medicinal plant, Calotropis procera (Aiton) W.T. Aiton, and its associated endophytes, Bacillus siamensis and Bacillus amyloliquefaciens, as the first matching study regarding the production of bioactive secondary metabolites from the plant vis-a-vis its bacterial endophytes.Secondary metabolites of both the plant and its endophytic bacteria were extracted using different solvents, e.g., water, methanol, and ethyl acetate. All extracts exhibited high quantities of phenolics, flavonoids, tannins, and saponins. In addition, they showed significant antioxidant capacity which was found to be positively correlated with total phenolic contents. The highest total antioxidant capacity (99.28 ± 0.0 mg AA equivalent/g extract) was measured for the aqueous extract of B. siamensis.Antibacterial activity of the different extracts was evaluated against certain pathogenic bacteria, i.e., Escherichia coli, Klebsiella pneumoniae, Streptococcus agalactiae, Salmonella typhi, Serratia marcescens, and Staphylococcus aureus. It was strikingly found that the broadest antibacterial spectrum was revealed by extracts of both C. procera and its endophytic B. siamensis. Interestingly, antibacterial activity was significantly correlated to phenolic and flavonoid contents.
Subject(s)
Bacillus amyloliquefaciens/chemistry , Bacillus/chemistry , Calotropis/chemistry , Calotropis/microbiology , Plants, Medicinal/chemistry , Plants, Medicinal/microbiology , Anti-Bacterial Agents/chemistry , Anti-Bacterial Agents/pharmacology , Antioxidants/analysis , Bacillus/physiology , Bacillus amyloliquefaciens/physiology , Bacteria/drug effects , Endophytes/chemistry , Endophytes/physiology , Flavonoids/analysis , Microbial Sensitivity Tests , Phenols/analysis , Plant Extracts/chemistry , Staphylococcus aureus , Tannins/analysisABSTRACT
In the present study the production of α-glycosidase inhibitors was used as a strategy to screen endophytic fungi with insecticidal and antifungal potential. Endophytic fungi were isolated from Calotropis gigantea L. (Gentianales: Apocynaceae) and evaluated for their α-glycosidase inhibitory activity. Maximum inhibitory activity was observed in an isolate AKL-3, identified to be Alternaria destruens E.G.Simmons on the basis of morphological and molecular analysis. Production of inhibitory metabolites was carried out on malt extract and partially purified using column chromatography. Insecticidal potential was examined on Spodoptera litura Fab. (Lepidoptera: Noctudiae). Partially purified α-glycosidase inhibitors induced high mortality, delayed the development period as well as affected the adult emergence and induced adult deformities. Nutritional analysis revealed the toxic and antifeedant effect of AKL-3 inhibitors on various food utilization parameters of S. litura. They also inhibited the in vivo digestive enzymes activity in S. litura. Partially purified α-glycosidase inhibitors were also studied for their antifungal potential. Inhibitors demonstrated antifungal activity against the tested phytopathogens inducing severe morphological changes in mycelium and spores. This is the first report on production of α-glycosidase inhibitors from A. destruens with insecticidal and antifungal activity. The study also highlights the importance of endophytes in providing protection against insect pests and pathogens to the host.
Subject(s)
Alternaria/metabolism , Calotropis/parasitology , Endophytes/metabolism , Glycoside Hydrolase Inhibitors/pharmacology , Plant Diseases/prevention & control , Spodoptera/drug effects , Animals , Antifungal Agents/isolation & purification , Antifungal Agents/metabolism , Antifungal Agents/pharmacology , Calotropis/microbiology , Glycoside Hydrolase Inhibitors/isolation & purification , Glycoside Hydrolase Inhibitors/metabolism , Insecticides/isolation & purification , Insecticides/metabolism , Insecticides/pharmacology , Larva/drug effects , Larva/growth & development , Plant Diseases/microbiology , Plant Diseases/parasitology , Spodoptera/growth & developmentABSTRACT
Endophytes, a potential source of bioactive secondary metabolites, were isolated from the widely used medicinal plant Calotropis procera Ait. Approximately 675 segments from 15 Calotropis procera plants and 15 latex samples were assessed for the presence of endophytic fungi. Finally, eight fungal species were isolated and identified based on their macro- and micro-morphology. The endophytic fungal filtrates were screened for their antimicrobial activity against 11 important pathogenic micro-organisms. The filtrates of nanoparticles were from three of the eight isolated endophytic fungi, namely, Penicillium chrysogenum, Aspergillus fumigatus and Aspergillus flavus, and were highly effective against the tested bacteria, while the remaining endophytic fungal filtrates displayed low activity.
