A new lignan glycoside from the stems of Zanthoxylum armatum DC

Abstract A new lignan glycoside, (7S,8R)-guaiacylglycerol-ferulic acid ether-7-O-β-D-glucopyranoside (1), along with five known phenylpropanoids (2–6) and seven phenylpropanoid glycosides (7–13), were isolated from the stems of Zanthoxylum armatum DC. Their structures were elucidated by spectroscopic analysis. Compounds 2–8 and 11–13 were first isolated from Rutaceae and the others were isolated for the first time from Z. armatum.


Result and discussion
Compound 1 was obtained as colourless oil. Its molecular formula was determined as C 26 H 32 O 13 by HR-eSI-MS at m/z 575.1739 [M + Na] + , possessing 11° of unsaturation. The 1 H NMR spectrum of 1 (Table S1)  In the 13 C NMR spectrum, the presence of two C 6 -C 3 units arising from lignan and a glucopyranose was suggested. The proton and carbon signals were assigned with the 1 H-1 H COSY, HMBC and HMQC. The correlation site between the guaiacylglycerol and the ferulic acid moiety was established by a HMBC experiment ( Figure S1) in which the long-range correlation between H-8 (δ 3.86) and C-4′ (δ 147.5) was observed. Acid hydrolysis of 1 with 5% HCl afforded d-glucose, which compared with authentic samples. The stereochemistry of the anomeric carbon of glucose was determined as β according to the coupling constant of the anomeric proton and the chemical shift of C-1″ (102.3). The glycosidic site was unambiguously established by a HMBC experiment in which the longrange correlation between H-1″ (δ 4.61) and C-7 (δ 79.7) was observed. The small coupling constant (J 7,8 = 4.5 Hz) in the 1 H NMR spectrum indicated a erythro configuration between H-7 and H-8. The CD spectrum of 1 showed a negative Cotton effect at 238 nm, together with the clear NOeSY correlations between H-8/H-2 and H-8/H-6 ( Figure S1), indicated the 7S,8R-configuration (Matsuda & Kikuchi 1996;Hu et al. 2012). Finally, structure of 1 was defined as (7S,8R)-guaiacylglycerol-β-ferulic acid ether-7-O-β-d-glucopyranoside.
Twelve known compounds were identified as erythro-1-(4-hydroxyphenyl) glycerol (2) (Qiao et al. 2006) and isopsoralenoside (13) (Qiao et al. 2006). Their structures were established on the basis of spectral and chemical evidence, which were in good agreement with those reported in the literature. Among that, compounds 2-8 and 11-13 were first isolated from Rutaceae and others were isolated for the first time from Z. armatum.

Plant materials
The stems of Z. armatum DC. was collected from Nanning of Guangxi Province, China in September 2014, and identified by associate professor Ze-hao Huang, and a voucher specimen of the plant (#Z140934) was deposited in school of life science and engineering, lanzhou University of Technology, Gansu, China.

Conclusion
The Z. armatum (Rutaceae) is widely distributed in China, which has been used as Traditional Chinese Medicine. Chemical study on the stems of Z. armatum has resulted in the isolation of a new phenylpropanoid glycoside, (7S,8R)-guaiacylglycerol-β-ferulic acid ether-7-O-β-dglucopyranoside (1), along with 12 known compounds. Compounds 2-8 and 11-13 were first isolated from Rutaceae and others were isolated for the first time from Z. armatum.

Supplementary material
Supplementary material relating to this article is available online, alongside Tables S1 and Figures S1-S5.

Disclosure statement
No potential conflict of interest was reported by the authors.

Funding
This research was supported by the National Natural Science Foundation of China [grant number 81360476].