Chemical Constituents of the Root of Jasminum giraldii

abstract: Two new compounds, ethylconiferin (1) and (−)-lariciresinol 4-(6'''-O-cinnamyl-β-D-glucopyranoside) (2), along with the three known compounds (+)-pinoresinol (3), (+)-cycloolivil (4), nobiletin (5), were isolated from the root of Jasminum girialdii. All these compounds were isolated for the first time from this source. Their structures were elucidated on the basis of extensive spectroscopic analysis and chemical methods. In addition, the in vitro cytotoxic activity of these compounds was evaluated. The results showed that none of the compounds had any significant inhibitory activities on the proliferation of HCT-116 and SW-620 cells.


Introduction
Jasminum giraldii Diels (Oleaceae), is an endemic plant which is found distributed at an altitude of 300-1,500 m, in valleys and shrubbery of the Qinba Mountains in China's Shaanxi Province [1], Its dried roots, named as "quan pi" in Chinese, are used as a traditional local herb for the treatment of various diseases, such as fractures, traumatic injury and blood stasis, while some other species of this genus are employed to treat dysmenorrhea, metritis, leucorrhoea, galactophoritis, puerperal infection, irregular menstruation, hyperthermia, arthralgia, pain due to ischemia, dermatitis [2], fever, rheumatic pain [3], dysenteric diarrhea, trachelopanus, eczema [4], giddiness, edema [5] in Traditional Chinese Medicine.
The chemistry and pharmacology of the ethanol extracts of the roots of J. giraldii have never been systematically investigated. As part of a program to acquire and assess potent chemicals in several traditional Chinese medicines for the preservation and treatment of colorectal cancer [6][7][8][9], an ethanolic extract of the root of J. giraldii has been investigated. We describe herein the isolation and structural elucidation of two new compounds 1,2 ( Figure 1) along with three known compounds 3-5 [10][11][12]. Furthermore, the cytotoxic activity of these compounds against HCT-116 and SW-620 cells is reported for the first time.

General
UV spectra were taken with a HALO DB-20R UV-VIS spectrophotometer. Optical rotations were recorded on a PerkinElmer Model 343 polarimeter. The IR spectra were recorded on a Shimadzu FTIR-8400S instrument. ESI-MS was performed on s Waters Quattro Premier instrument. The HR-ESIMS spectra was taken on an Agilent Technologies 6550 Q-TOF. 1D and 2D NMR spectra were recorded on a Bruker-AVANCE500 instrument with TMS as an internal standard. The analytical HPLC was performed on a Waters 2695 Separations Module coupled with a 2996 Photodiode Array Detector and a ODS-3 column (4.6 × 250 mm, 5 ìm particles, Inertsill, Tokyo, Japan). Semipreparative HPLC was performed on a system comprising a Shimadzu LC-6AD pump equipped with a SPD-20A UV detector and a Ultimate XB-C18 (10 × 250 mm, 5 μm particles) or Allsphere ODS-2 (10 × 250 mm, 5 μm particles). Sephadex LH-20 was purchased from GE Healthcare Bio-Sciences AB (Uppsala, Sweden). MCI GEL was from Mitsubishi Chemical Corporation (Tokyo, Japan). C-18 (40-75 μm) silicagel was purchased from SiliCycle Corporation (Quebec, Canada). D101 was from Sunresin New Materials Co. Ltd. (Xi'an, China). Silica gel was purchased from Qingdao Haiyang Chemical Group Corporation (Qingdao, China).

Plant Materials
The root of Jasminum giraldii Diels. was collected on October in 2009 in Shanxi, China, and authenticated by Prof. Yaowu Guo. A voucher specimen has been deposited in the Department of Collaborative Innovation Center for Chinese Medicine in Qingba Mountains, School of Pharmacy the Fourth Military Medical University.

Acid Hydrolysis of 2
A solution of compound 2 in 0.5 M H 2 SO 4 (2.0 mL) was heated under reflux for 3 h. After cooling, the reaction mixture was diluted with H 2 O, neutralized with BaCO 3 , then filtered. The solution was extracted with EtOAc for three times (3 × 3 mL) to obtained the EtOAc extract and H 2 O layer after removing the solvents. The aqueous layer of the hydrolysate of compound 2 was evaporated and to yield glucose with positive optical rotations, and the value of [α] 20 D : was +42.5 (c 0.11, H 2 O). The solvent system MeCN/H 2 O (6:1) was used for the TLC analysis of glucose and authentic sugar samples.

Bioassay for Cytotoxic Activity
The human colon cell line HCT-116 and SW620 was obtained from the Shanghai Institute of Cell Biology. The cells were maintained in DMEM medium supplemented with 10% FBS, penicillin (100 U/mL) and streptomycin (100 mg/mL) at 37 °C in a humidified atmosphere with 5% CO 2 . Cell proliferation of HCT-116 cells was assessed by conducting colorimetric MTT cell proliferation assay. Briefly, a limited number of growing cells were seeded into 96-well cell culture plate and were maintained for 24 h so that they became attached to the bottom of the well. The medium was aspirated and new medium (200 µL) including three groups of concentrations (10 −4 , 10 −5 , 10 −6 M) of compounds were added to parallel wells. The cells were incubated at 37 °C in a humidified atmosphere for 24 h. Twenty µL of MTT solution was added and the incubation continued for 4 h. The pure formazan product was then solubilized by 150 µL DMSO. The plates were read at 570 nm using a microtiter plate reader.

Conclusions
Compounds 1, 2 were new glycosides and together with compounds 3-5 were isolated from the Jasminum genus for the first time. Compounds 1-5 were assayed for their cytotoxic activity, and the data proved that none of the compounds had any significant inhibitory activities on proliferation of HCT-116 cells and SW-620 cells at the concentrations of 1-10 M.