A New Dihydrocoumarin from Ficus sycomorus
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A NEW DIHYDROCOUMARIN FROM Ficus sycomorus
Samia M. El-Sayyad,1 Makboul A. Makboul,1 Rofida Wahman,1,2 and Salwa F. Farag1,3*
A phytochemical study of the fruits and leaves of Ficus sycomorus L. led to the isolation of a new dihydrocoumarin, 4-carboxylic-4-hydroxy-3,4-dihydrocoumarin (1), together with ten known compounds. Moreover, the different extracts of F. sycomorus were screened for cytotoxic activity using the brine shrimp lethality bioassay. The results revealed that all extracts were virtually nontoxic on the shrimps and showed LC50 values greater than 100 μg/mL. Keywords: Ficus sycomorus, dihydrocoumarin, isoquercitrin, cinaroside, brine shrimp lethality bioassay. Ficus sycomorus L. is an evergreen spreading tree and grows in Egypt. The comparatively large fruit is edible and called gimmeiz [1, 2]. Our previous biological study of the different extracts of F. sycomorus L. showed significant hepatoprotective and hypotensive activities [3, 4]. Each of the ethanolic extract of F. sycomorus L. fruits and leaves was partitioned separately with n-hexane, CHCl3, EtOAc, and n-BuOH, successively. By several chromatographic techniques a new compound, 4-carboxylic-4-hydroxy-3,4dihydrocoumarin (1), together with ten known compounds, was isolated. They were identified as ethyl-β-D-glucopyranoside (2) [5], ethyl-α-D-arabinofuranoside (3) [6, 7], vanillic acid (4) [8], quercetin-3-O-glucoside (isoquercitrin) (5), luteolin-7-Oglucoside (cinaroside) (6) [9–12], campesterol-3-O-glucoside (7) [13], and psoralen (8) [14, 15] by comparing their spectroscopic data with those described in the literature. In addition, β-amyrin (9), β-sitosterol (10), and β-sitosterol-3-O-glucoside (11) were identified by comparison with authentic samples (mp and co-TLC). The UV (MeOH) absorption spectrum of compound 1 showed maxima at 208 and 253 and a shoulder at 285 nm, suggesting a dihydrocoumarin skeleton [16]. Its IR spectrum showed absorption bands at 1715 cm –1 due to a saturated δ -lactone, a strong broad absorption band at 3417 cm–1 due to OH and carboxylic OH groups, 1587 (CH2) and 1024 (COC) [17]. The 1H NMR spectrum revealed two signals at δ 1.97 and 2.33 (each 1H d, J = 15.0 Hz) assigned to C-3 pyran. Also, a pattern of 1,2-disubstituted benzene signals appeared at δ 6.76 (1H, d, J = 7.7 Hz), 6.89 (1H, br.t, J = 7.4 Hz), 7.14 (1H, td, J = 7.7, 0.8 Hz), and 7.33 (1H, d, J = 7.4 Hz) [18]. The 13C NMR and DEPT spectra exhibited signals closely correlated with those expected for the 3,4-dihydrocoumarin skeleton at δ 42.2 (t), 73.8 (s), 109.3 (d), 121.3 (d), 123.9 (d), 128.3 (d), 134.1 (s), 141.1 (s), and 174.2 (s) [19] in addition to one carbonyl carbon of the carboxylic group at δ 178.8 (s). The disubstitution at C-4 was indicated by the appearance of the quaternary carbon at 73.8 (s). The structure was confirmed by 1H–1 H COSY, HSQC, and HMBC experiments. The EI-MS spectrum did not show the molecular ion peak but it showed a peak at m/z 149 [M – (CH2 + CO + OH)]+ from the retro-Diels-Alder reaction characteristic for 4-substituted 3
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