Chemical Constituents of Suaeda salsa and their Cytotoxic Activity

Suaeda salsa (L.) Pall. (Chenopodiaceae) is represented by 20 species in China [1]. It also one of the most important halophyte and has important economic value because its seeds contain approximately 40% oil, rich in unsaturated fatty acids, which can be easily converted to chemical compounds for industrial and pharmaceutical use [2]. It has been used as a nutrient vegetable by local residents and received growing attention due to its pharmaceutical importance in recent years [3]. Studies on modern pharmacology show that it has been used to treat hyperglycemia, hypertension, cardiovascular diseases, and so on. However, no phytochemical investigations have been reported on this plant. This paper describes the isolation and structural elucidation of ten known metabolites, three lignans: (–)-syringaresinol (1), (–)-syringaresinol-4-O-D-glucopyranoside (2), and syringin (3); two phenolic acids: syringic acid (4), and syringic acid-D-glucopyranosyl ester (5); and others: adenosine (6), adenine (7), -daucosterol (8), uracil (9), and -sitosterol (10). The structures of compounds were established based on chemical and spectral methods. All compounds were isolated from this plant for the first time. Compounds 1–3 were evaluated for their in vitro cytotoxicity determined by the MTT colorimetric method. Compound 2 showed moderate activity against four cell lines, HL-60 (promyelocytic leukemia), MCF-7 (breast carcinoma), HepG2 (liver carcinoma), and A549 (lung carcinoma), with IC50 values of 36.18, 51.87, ~100, and > 100 M, respectively. General Comments. Melting points were measured using a XT-4 Boetius micro melting point apparatus and were uncorrected. IR spectra were detected on a Nexus 870 FT-IR spectrometer. HR-ESI-MS spectra were measured on an Agilent 6520 UPLC/Q-TOF/MS spectrometer. NMR data were acquired on a Bruker DRX500 or 300 NMR spectrometer with 1H and 13C NMR observed at 500 or 300 and 125 or 75 MHz, and all chemical shifts ( ) are given in ppm with reference to the solvent. Silica gel (200–300 mesh) for column chromatography was obtained from Qingdao Marine Chemical Factory, Qingdao, China. Sephadex LH-20 was purchased from Pharmacia Biotech, Sweden. HPLC analyses were performed with a column of Allsphere ODS-2.5 m (250 4.6 mm), Agilent pump 1100, and ELSD detector Alltech 500. All other chemicals used in this study were of analytical grade. TLC analyses were carried out on silica gel 60 F254 (Merck) plates. The compounds were monitored by spraying 1% vanillin-H2SO4 reagent, followed by heating at 105 C for 1–2 min. The spectral data of the purified compounds are reported below.