Hydroxycinnamic acid amide profile of Solanum schimperianum Hochst by UPLC-HRMS

⿢A new hydroxycinnamic acid amide (HCAA) ⿿ Nε-feruloyl lysine was isolated from root extract of Solanum schimperianum..⿢16 known HCAAs were tentatively identified by Orbitrap LC-HR-MS/MS.⿢The antioxidant potential (DPPH, ABTS and FRAP) of Nε-feruloyl lysine was greater than that of the root extract.⿢Nε-feruloyl lysine exhibited good (MIC/MBC = 349 μM) activity, against Staphylococcus aureus 3359 and ATCC 6538 P strains.

A newly discovered Nε-feruloyl lysine (1) together with 16 known hydroxycinnamic acid amides (HCAAs) were identified in the roots of Sudanese plant Solanum schimperianum Hochst (syn. Solanum carense Dunal, Solanaceae). The structure of 1 was established on the basis of 1D (1H, 13C NMR) and 2D (1H-1H COSY, 1H-13C HSQC) NMR analysis, together with UV⿿vis, HR-ESI⿿MS and ESI⿿MS2 fragmentation analyses. HCAAs were analyzed using liquid chromatography coupled to an Orbitrap mass spectrometer (ThermoScientific) using parallel-reaction monitoring (PRM) mode. For the first time, eight HCAAs including agmatine and cadaverine amides, as well as Nε-feruloyl lysine and sinapoyl putrescine, were reported in genus Solanum.Nε-feruloyl lysine and the hydromethanolic extract of S. schimperianum roots were evaluated for their antioxidant activity using free radical DPPH and ABTS scavenging, and ferric reducing power (FRAP) methods. The antimicrobial activity was estimated on a panel of pathogenic bacteria and fungi by the broth microdilution method (BMD). Nε-feruloyl lysine demonstrated stronger DPPH (IC50 85.83 μg/ml), ABTS (IC50 255.54 μg/ml) and FRAP (0.44 ± 0.02 mM TE/mg dw) activity compared to the root extract. Nε-feruloyl lysine exhibited significantly higher antimicrobial activity against both Staphylococcus aureus strains NBIMCC 3359 (MIC/MBC 112.5 μg/ml) and penicillin resistant ATCC 6538P (MIC 112.5 μg/ml) than the total S. schimperianum extract (MIC 1.25 and 2.5 mg/ml, respectively). The extract showed antimicrobial activity towards Streptococcus pyogenes, Listeria monocytogenes and Candida albicans (MIC 1.25 mg/ml). Nε-feruloyl lysine had function for the observed protection against oxidative stress and antimicrobial activity.

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