Estimation of in vitro antioxidant and antimicrobial potential of French marigold (Tagetes patula L.) extracts

Abstract

Methanol and aqueous extracts of French marigold flowers and leaves, with previously determined chemical profiles, were subjected to in vitro antioxidant and antimicrobial assays. The methanol extract of flowers had the highest total phenolic content (TPC) according to the Folin–Ciocalteu method, and UHPLC–LTQ/orbitrap/MS analysis identified the flavonoid aglycones as the dominant class of phenolics in the extract. Likewise, the methanol extract of flowers showed the highest antioxidant activity measured by DPPH and ABTS assays. Generally, the higher TPC correlated with lower IC50 value and stronger antioxidant potential in all extracts. Microdilution test was used for determination of the minimum inhibitory (MIC) and minimum fungicidal (MFC) concentrations of French marigold extracts on following microfungi - Aspergillus versicolor, A. niger, Penicillium ochrochloron, P. verrucosum var. cyclopium and Alternaria alternata. The antimicrobial test revealed that P. ochrochloron was the most sensitive while A. niger was the most resistant microfungus to all analyzed extracts. Correspondingly, the methanol extract of flowers was shown to be the most potent one, regarding the antimicrobial activity. Additionally, antimicrobial potential of methanol extract of flowers was tested for in vivo potato tuber protection against A. alternata causing the early blight disease. Based on obtained antioxidant and antimicrobial potential, French marigold methanol extracts could provide an alternative strategy for the controlling expansion of potato pathogens.