Five acetophenones bearing spiroketal-hexofuranoside rings, one di-C-glycosidic acetophenone and two benzopyrans, along with 16 known compounds were isolated from the leaves of Melicope pteleifolia. Structures of all the isolates were elucidated using extensive spectroscopic methods, including 1D, 2D-NMR and HRESIMS. All the isolates were also evaluated for their neuraminidase inhibitory activities against H1N1, H9N2, wild-type H1N1 and oseltamivir-resistant H1N1 (H274Y mutation) virus strains. Of the isolates, tamarixetin 3-robinobioside was found to exhibit the strongest enzymatic inhibition (IC50 24.93 ± 3.46, 23.19 ± 5.41, 26.67 ± 5.16 and 40.16 ± 4.50 μM, respectively). Selected candidates, kaempferol 3-robinobioside, kaempferol 3-O-β-d-glucopyranosyl (1 → 2)-α-d-xylopyranoside and tamarixetin 3-robinobioside, also showed moderate reductions in H1N1-induced cytopathic effects on MDCK cells.
Keywords: H1N1; Melicope pteleifolia; Neuraminidase; Rutaceae; Spiroketal.
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