Evaluation of chemical composition, secondary metabolites (phenol, flavonoid), antioxidant effect and biological activities of Golden rain leaves

This study evaluates the antioxidant and antimicrobial activities of methanolic extract of Goldenrain leaves on various plant pathogens that commonly cause irreparable damages to agricultural crops.Also, total phenolic and flavonoid content was determined. Antimicrobial activity was tested against 14microorganisms, including three gram-positive (Bacillus subtilis, Staphylococcus aureus andRathayibacter toxicus), five gram-negative (Escherichia coli, Pseudomonas aeruginosa, Pseudomonassyringae subsp. syringae, Pseudomonas viridiflava and Xanthomonas campestris pv. campestris) bacteriaand six (Pyricularia grisea, Fsarium oxysporum, Sclerotinia sclerotiorum, Botrytis cinerea, Rhizoctoniasolani and Alternaria alternata) fungi, using disk diffusion method and the Minimum InhibitoryConcentration (MIC) technique. The Golden rain leaves were also subjected to screening for possibleantioxidant activity by using catalase, peroxidase, superoxide dismutase and 2, 2-diphenyl-1-picrylhydrazyl(DPPH) assay. The methanolic extract showed significant activity against S. aureus (MIC = 25 μg/mL),and P. oryzae (MIC = 12.5 μg/mL). In addition, the free radical scavenging capacity of the extract wasdetermined with an IC50 value of 113.17 μg/mL. Furthermore, structure of the compounds was determinedby means of Liquid chromatography with UV and MS detection (LC/UV/ESI-MS). Using this method ofanalysis, we detected up to three saponin and acyclic sesquiterpene oligoglycoside. The plant producesthese compounds as a complex mixture of naturally non-regiosselective acetylated glycosides. Our resultssuggest that this plant may be a potential source of biocide, for economical and environmentally friendlydisease control strategies. It may also be a good candidate for further biological and pharmacologicalinvestigations.

Keywords:

Antimicrobial activity , Antioxidant activity , Koelreuteria paniculata Laxm , Phytochemicals , Plant pathogens