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Isolation and characterization of structurally novel antimutagenic flavonoids from spinach (Spinacia oleracea)
R Edenharder1, G Keller, K L Platt
1Department of Hygiene and Environmental Medicine, University of Mainz, Obere Zahlbacher Strasse 67, D-55131 Mainz, Germany. edenhard@uni-mainz.de
Abstract:
Thirteen compounds, isolated from spinach (Spinacia oleracea), acted as antimutagens against the dietary carcinogen 2-amino-3-methylimidazo[4,5-f]quinoline in Salmonella typhimurium TA 98. The antimutagens were purified by preparative and micropreparative HPLC from a methanol/water (70:30, v/v) extract of dry spinach (commercial product) after removal of lipophilic compounds such as chlorophylls and carotenoids by solid-phase extraction (SPE). Pure active compounds were identified by instrumental analysis including FT-IR, (1)H and (13)C NMR, UV-vis spectroscopy, and mass spectrometry. All of these compounds were flavonoids and related compounds that could be attributed to five groups: (A, methylenedioxyflavonol glucuronides) 5,3'-dihydroxy-4'-methoxy-6,7-methylenedioxyflavonol 3-O-beta-glucuronide (compound 1), 5,2',3'-trihydroxy-4'-methoxy-6,7-methylenedioxyflavonol 3-O-beta-glucuronide (compound 2), 5-hydroxy-3',4'-dimethoxy-6,7-methylenedioxyflavonol 3-O-beta-glucuronide (compound 3); (B, flavonol glucuronides) 5,6,3'-trihydroxy-7,4'-dimethoxyflavonol 3-O-beta-glucuronide (compound 4), 5,6-dihydroxy-7,3',4'-trimethoxyflavonol 3-O-beta-glucuronide (compound 5); (C, flavonol disaccharides) 5,6,4'-trihydroxy-7,3'-dimethoxyflavonol 3-O-disaccharide (compound 6), 5,6,3',4'-tetrahydroxy-7-methoxyflavonol 3-O-disaccharide (compounds 7 and 8); (D, flavanones) 5,8,4'-trihydroxyflavanone (compound 9), 7,8,4'-trihydroxyflavanone (compound 10); (E, flavonoid-related compounds) compounds 11, 12, and 13 with incompletely elucidated structures. The yield of compound 1 was 0.3%, related to dry weight, whereas the yields of compounds 2-13 ranged between 0.017 and 0.069%. IC(50) values (antimutagenic potencies) of the flavonol glucuronides ranged between 24.2 and 58.2 microM, whereas the flavonol disaccharides (compounds 7 and 8), the flavanones (compounds 9 and 10), and the flavonoid-related glycosidic compounds 11-13 were only weakly active. The aglycons of compounds 7 and 8, however, were potent antimutagens (IC(50) = 10.4 and 13.0 microM, respectively).
Insights
Spinach compounds, primarily flavonoids, show antimutagenic activity against a dietary carcinogen. Certain flavonol glucuronides and aglycones exhibit significant potency, highlighting spinach as a source of natural antimutagens.
Area of Science:
- Phytochemistry
- Natural Products Chemistry
- Food Science
Background:
- Dietary carcinogens pose health risks.
- Spinach (Spinacia oleracea) is a common vegetable with potential health benefits.
- Identifying natural antimutagens is crucial for cancer prevention strategies.
Purpose of the Study:
- To isolate and identify antimutagenic compounds from spinach.
- To evaluate the antimutagenic activity of these compounds against 2-amino-3-methylimidazo[4,5-f]quinoline.
- To characterize the chemical structures of the active spinach constituents.
Main Methods:
- Extraction of dry spinach using methanol/water.
- Solid-phase extraction (SPE) to remove lipophilic compounds.
- Preparative and micropreparative High-Performance Liquid Chromatography (HPLC) for purification.
- Instrumental analysis including FT-IR, NMR, UV-vis, and mass spectrometry for structural elucidation.
Main Results:
- Thirteen compounds with antimutagenic activity were isolated from spinach.
- These compounds were identified as flavonoids and related substances, categorized into five groups.
- Flavonol glucuronides (compounds 4-5) showed moderate activity (IC50: 24.2–58.2 μM).
- Aglycones of compounds 7 and 8 exhibited potent antimutagenic activity (IC50: 10.4–13.0 μM).
Conclusions:
- Spinach contains multiple flavonoid compounds with significant antimutagenic properties.
- Specific flavonol glucuronides and their corresponding aglycones are key contributors to spinach's antimutagenic effects.
- These findings support the role of spinach consumption in mitigating risks associated with dietary carcinogens.