New Phenanthrene Derivatives and a Flavonoid Glycoside Dihexanoate From Malpighia glabra

Five previously undescribed compounds, including four rare phenanthrene derivatives, designated as malglabins A-D (1-4), and an unusual flavonoid glycoside dihexanoate, named kaempferol 3-O-(3'',4''-di-O-caproyl)-α-L-rhamnopyranoside (5), along with 12 known compounds, were isolated from the leaves and twigs of Malpighia glabra. Their structures (Figure 1) were elucidated through comprehensive spectroscopic analysis (high-resolution electrospray ionization mass spectrometry and one-/two-dimensional nuclear magnetic resonance) complemented by chemical derivatization study and electronic circular dichroism calculations. In biological evaluations, compounds 3 and 4 exhibited weak cytotoxicity against A549 human lung adenocarcinoma cells (IC₅₀ = 34.71 ± 0.48 and 30.66 ± 0.67 µM, respectively), while none of the tested compounds demonstrated anti-inflammatory activity in lipopolysaccharide-stimulated RAW264.7 macrophages at concentrations up to 50 µM.