Flavonoid Glucuronides and a Chromone from the Aquatic Macrophyte Stratiotes aloides

The first phytochemical analysis of the aquatic macrophyte Stratiotes aloides afforded two new flavonoid glucuronides, luteolin 7-O-β-d-glucopyranosiduronic acid-(1→2)-β-d-glucopyranoside (1) and chrysoeriol 7-O-β-d-glucopyranosiduronic acid-(1→2)-β-d-glucopyranoside (2), as well as the new 2-(2-hydroxypentyl)-5-carboxy-7-methoxychromone (5) and chrysoeriol 7-O-β-(6-O-malonyl)glucopyranoside (3), which has been assigned via NMR data for the first time. Additionally, free amino acids such as tryptophan, arginine, leucine, isoleucine, phenylalanine, and tyrosine along with choline, cis-aconitic acid, the phenolic glycoside α-arbutine, the chlorophyll derivative phaeophorbide a, and the flavonoid glycoside luteolin 7-O-β-(6-O-malonyl)glucopyranoside (4) were isolated. Despite the low quantities obtained in some cases (between 50−300 μg), the structures of all compounds were unambiguously elucidated by extensive NMR and MS experiments. With a delay of 2 days compound 1 (10 and 50 μM test concentration) strongly inhibited the growth of human SH-SY5Y neuroblastoma cells in a dose-dependent manner, whereas only a moderate growth inhibition of human Patu 8902 carcinoma cells could be observed. Compounds 1 and 2 showed no activities against the bacteria Escherichia coli BW25113, Pseudomonas pudida KT2440, and Enterobacter cloacae subsp. dissolvens.