Phenylpropanoids from Sparganium stoloniferum and their antiplatelet aggregation activities

Abstract Four new ferulic acid sucrose esters, β-D-(1-O-acetyl-6-O-trans-feruloyl)fructofuranosyl-a-D-2',6'-O-diacetylglucopyranoside (1), β-D-(1-O-acetyl-6-O-trans-feruloyl)fructofuranosyl-a-D-2',4'-O-diacetylglucopyranoside (2), β-D-(6-O-trans-feruloyl)fructofuranosyl-a-D-2',4',6'-O-triacetylglucopyranoside (3), β-D-(1-O-acetyl-6-O-trans-feruloyl)fructofuranosyl-a-D-4',6'-O-diacetylglucopyranoside (4), together with four known phenylpropanoids (5–8) were isolated from the rhizome of Sparganium stoloniferum (Graebn.) Buch.-Ham. ex Juz. Their structures were elucidated by chemical evidence and spectral analysis. Compounds 1–8 exhibited obvious inhibitory effects on ADP-induced platelet aggregation.


Introduction
The rhizome of Sparganium stoloniferum (Graebn.) Buch.-Ham. ex Juz., named "Sanleng", is applied to cure the syndrome of blood stasis in traditional Chinese medicine. Previous chemical investigations on this species have resulted in the isolation of phenylpropanoids [1][2][3][4], alkaloids [5], isocoumarins [6], cyclic dipeptides [7] and stilbenoid derivatives [6].  .0 (C-9 00 ) and d C 81.1 (C-5) indicated that the trans-feruloyl group was linked to C-6 of sucrose moiety. Furthermore, 1 H and 13 C NMR spectra also revealed the presence of three acetyl  ) with d C 173.1 indicated that three acetyl substituents were located at C-1 of the glucosyl moiety and C-2 0 , C-6 0 of the fructosyl moiety respectively. Thus, the structure of compound 1 was established as

Results and discussion
Compounds 2, 3, and 4 have the same molecular formula C 28 H 36 O 17 to compound 1 according to their HRESIMS ([M þ Na] þ ion peaks at m/z 667.1838, 667.1833, and 667.1850 for 2, 3, and 4, respectively). The 1 H-NMR and 13 C-NMR spectra of compounds 2, 3, and 4 showed highly similarity to those of compound 1, except for the positions of three acetyl substituents. This evidence suggested that compounds 2, 3, Compounds 5-8 were obtained as colorless amorphous solids and identified by comparison of their spectral and physical data with those described in the literature [8][9][10].
Compounds 1-8 were subjected to antiplatelet aggregation test, using rat PRP induced by ADP. The results are presented in Table 1. At a concentration of 0.5 mg/ ml, all compounds showed obvious inhibitory effects on platelet aggregation induced by ADP and compound 3 showed the most potent activity with inhibitory rate of 38.7%. It is reported that ethyl ferulate has stronger antiplatelet aggregation effect than ferulic acid [11]. This experiment indicated that methyl ester, glyceride, sucrose ester of ferulic acid, p-coumaric acid, and its glyceride all have antiplatelet aggregation effect. The glycerol ester and sucrose ester derivatives of ferulic acid have stronger activity than methyl ester derivatives.

General experimental procedures
Optical rotations were measured on a JASCO model 1020 polarimeter (Horiba, Tokyo, Japan

Plant materials
The rhizomes of Sparganium stoloniferum were purchased from Chinese Materia Medica Market in the Zhangshu city of Jiangxi Province, China and was identified by Professor Ke-Zhong Deng (Jiangxi University of Traditional Chinese Medicine, China). A voucher specimen (No. 160613) of the plant has been deposited in our school.

Alkaline hydrolysis of 1 to 4
Each sucrose ester sample (4 mg) was dissolved in 1% NaOH/MeOH (4 ml) separately, and the solution was stirred at room temperature for 5 h. The reaction mixture was neutralized with 1 N HCl and then extracted with CHCl 3 . The aqueous layer was applied to silica gel CC, eluting with

Antiplatelet aggregation activities
The inhibitor (2.0 mg) was dissolved in 1 ml of 10%DMSO to form a solution at the concentration of 2 mg/ml, which was diluted further to afford solutions at the concentration of 0.5 mg/ml and 0.1 mg/ml. Antiplatelet aggregation assays were based on a method reported by H. Yang et al [12]. Aspirin (0.5 mg/ml; 0.1 mg/ml) was used as positive control. Inhibitory rate of platelet aggregation ¼ (Maximum aggregation rate of blank solution -Maximum aggregation rate of sample solution)/Maximum aggregation rate of blank solution Â 100%.

Disclosure statement
No potential conflict of interest was reported by the author(s).

Funding
This work was financially supported by the National Natural Science Foundation of China under [Grant number 81860699].