Next Article in Journal
Baseline Serum Biomarkers Predict Response to a Weight Loss Intervention in Older Adults with Obesity: A Pilot Study
Next Article in Special Issue
Non-Targeted Metabolomic Analysis of Arabidopsis thaliana (L.) Heynh: Metabolic Adaptive Responses to Stress Caused by N Starvation
Previous Article in Journal
Metabolomics and Self-Reported Depression, Anxiety, and Phobic Symptoms in the VA Normative Aging Study
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Metabolites
Volume 13
Issue 7
10.3390/metabo13070852
metabolites-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles thumb_up
...
Endorse textsms
...
Comment
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Chemical Constituents of Euphorbia stracheyi Boiss (Euphorbiaceae)

by
Hui Zhu
1,2,†,
Xiangxiang Ren
1,2,†,
Yanbo Huang
2,
Tao Su
1 and
Lei Yang
2,*
1
Co-Innovation Center for Sustainable Forestry in Southern China, College of Biology and the Enviroment, Nanjing Forestry University, Nanjing 210037, China
2
Shanghai Key Laboratory of Plant Functional Genomics and Resources, Shanghai Chenshan Botanical Garden, Shanghai 201602, China
*
Author to whom correspondence should be addressed.
†
These authors contributed equally to this work.
Metabolites 2023, 13(7), 852; https://doi.org/10.3390/metabo13070852
Submission received: 19 May 2023 / Revised: 13 July 2023 / Accepted: 14 July 2023 / Published: 15 July 2023
(This article belongs to the Special Issue Identification of Secondary Metabolites by Multi-Omics Methods)
Browse Figures
Versions Notes

Abstract

:
Euphorbia stracheyi Boiss was used for hemostasis, analgesia, and muscular regeneration in traditional Chinese medicine. To study the chemical constituents of E. stracheyi, the ethyl acetate part of the methanol extract of the whole plant was separated by silica gel, sephadex LH-20 column chromatography, and semi-preparative HPLC. The isolation led to the characterization of a new lathyrane type diterpenoid, euphostrachenol A (1), as well as eleven known compounds (2–11), including a lathyrane, three ingenane-type and two abietane-type diterpenoids, two ionones, and two flavonoids. The structures of these compounds were established using 1D- and 2D-NMR experiments, mass spectrometry, and X-ray crystallographic experiments. The MTT method was used to determine the cytotoxic activity of five cancer cell lines (Leukemia HL-60, lung cancer A-549, liver cancer SMMC-7721, breast cancer MCF-7, and colon cancer SW480) on the isolated compounds. However, only compound 4 showed moderate cytotoxicity against these cell lines, with IC50 values ranging from 10.28 to 29.70 μM, while the others were inactive. Our chemical investigation also confirmed the absence of jatrophane-type diterpenoids in the species, which may be related to its special habitat.

1. Introduction

With nearly 2000 species, the genus Euphorbia (Euphorbiaceae) is the third largest genus in flowering plants, second only to Astragalus (Fabaceae) and Psychotria (Rubiaceae) [1]. Plants of Euphorbia are a rich source of structurally diverse macrocyclic and polycyclic diterpenoids, with more than twenty skeleton types, including casbane, jatrophane, daphnane, tigliane, lathyrane, myrsinane, premyrsinane, cyclomyrsinane, paraliane, pepluane, and ingenane [2,3]. The frameworks of these diterpenoids are further modified by different functional group substitutions at different positions and numbers, such as hydroxyl, epoxy, ether, acyl, polyester, and carbonyl groups, which makes the structure of these compounds even more complex and diversified. So far, more than 700 diterpenoids have been isolated from the genus Euphorbia, showing anti-tumor, multi-drug-resistance-reversing, anti-inflammatory, antibacterial, and pesticidal activities [2,3]. In 2012, the approval of ingenol 3-angelate (ingenol mebutate) by the U.S. Food and Drug Administration and European Medicines Agency for the treatment of actinic keratosis, a precancerous skin condition, attracted more interest in these types of diterpenoids [4].
Plant secondary metabolites are often lineage-specific, and the occurrence and content of secondary metabolites in a certain plant species could be determined by genetic and environmental factors. Thus, phylogenetically related plants in different habitats may harbor distinctive secondary metabolite profiles. For example, Salvia officianlis L. and S. miltiorrhiza are native to the Mediterranean and East Asia, respectively. While the former mainly contains tricyclic diterpenoids, the latter accumulates nor-diterpene quinones named tanshinones [5]. These differences could influence their pharmacological performances, since both species are medicinally highly valuable. Furthermore, the availability of closely related species with different secondary metabolite constituents allows us to elucidate the biosynthetic pathway of these natural products through a comparative genomics analysis [6]. Clearly, this phenomenon is important and should be given much attention in phytochemical research.
Euphorbia stracheyi Boiss is a perennial noxious weed mainly distributed in the western region of China, including Qinghai, Tibet, Sichuan, and Yunnan province [7]. While the near-cosmopolitan nature of Euphorbia is well acknowledged, E. stracheyi is one of the few plants that can grow in high-altitude alpine meadow regions (from 1000 to 4900 ASL). E. stracheyi roots were used as traditional medicine for hemostasis, analgesia, and muscular regeneration [6]. As such, extensive phytochemical investigations have been performed on this plant, which involved the isolation of flavonoids, coumarins, phenylpropanoids, ionones, steroids, triterpenoids, and its main components, diterpenoids [8,9,10,11,12,13,14]. The cytotoxic activity of the isolated compounds has been evaluated [10,11,13]. The structures of some common compounds are shown in Figure 1. Interestingly, although jatrophane-type diterpenoids are widely occurring in plants of Euphorbia, to date there are no compounds of this type isolated from the species. In order to further study the chemical composition of the species, the methanol extract of the whole plant of E. stracheyi was investigated in the present study, which led to the isolation and characterization of a new lathyrane diterpenoid, which was designated euphostrachenol A (1), together with eleven known compounds, including a lathyrane (2), three ingenane (3–5) and two abietane diterpenoids (6, 7), two ionones (8, 9), and two flavonoids (10, 11). The structures of the isolated compounds were determined through extensive spectroscopic analysis and X-ray crystallographic experiments. In the present study, we report the isolation, structure elucidation, and in vitro cytotoxic activity of these compounds.

2. Materials and Methods

2.1. Instruments and Materials

X-ray crystallographic analyses was performed on a Bruker APEX DUO X-ray single crystal diffractometer (Bruker, Rheinstetten, Germany). Optical rotations were recorded on a Jasco P1020 spectropolarimeter. IR spectra were measured on a NICOLET iS107 FTIR spectrometer (Thermo Fisher, Massachusetts, USA). NMR spectra were obtained on Bruker AVANCE III 500 MHz and AV 600 MHz superconducting NMR spectrometers (Bruker, Rheinstetten, Germany) with TMS as the internal standard. High-resolution MS data were obtained on an Agilent 1290 UPLC/6540 Q-TOF mass spectrometer in positive mode. UV spectroscopic data were recorded on a Shimadzu-210A double-beam spectrophotometer. Agilent 1290 UPLC/6540 Q-TOF (Agilent, Santa Clara, USA) was used to undertaken liquid chromatography/quadrupole time-of-flight mass spectrometry data.
Semi-preparations were performed on a high-performance liquid chromatograph (HPLC, Agilent 1260 series) using a SunFire-C18 column (5 μm, 10 mm × 250 mm) and an X Select HSS T3 (5 μm, 10 mm × 150 mm) column. Silica gel (100–200, 200–300, and 300–400) (Qingdao Ocean Chemical Co., Ltd., Qingdao, China), Lichroprep RP-18 (40–63 μm, Fuji, Tokyo, Japan), MCI gel CHP-20P (75–150 mm, Mitsubishi Chemical Corp., Tokyo, Japan), and Sephadex LH-20 (20–150 μm, Pharmacia, Shanghai, China) were used for column chromatography. The chromogenic agent was 8% ethanol sulfate, sprayed and heated appropriately for color development.
The whole plants of E. stracheyi (flowering) were collected in August 2020 from Gongshan County, Nujiang Prefecture, Yunnan Province. The plant sample was identified by Mr. Yan-Bo Huang of Shanghai Chenshan Botanical Garden. The age of the selected plants was two years, and the material was dried and extracted with methanol.
The sources of the strains used in this study were as follows: Leukemia HL-60, purchased from ATCC (item number: CCL-240, Tissue: Peripheral blood); Lung cancer cells A549, purchased from ATCC (Item number: CRM-CCL-185, Tissue: Lung); Breast cancer MDA-MB-231, purchased from ATCC (item number: CRM-HTB-26, Tissue: Breast); Intestinal cancer cell SW480, purchased from ATCC (item number: CCL-228, Tissue: Colon); Hepatocellular carcinoma cells SMMC-7721, purchased from BNCC, (item number: BNCC338089, Tissue: Liver). ATCC is an American-type culture collection.

2.2. Extraction and Separation

The crude extract was obtained by extracting the ion from powdered and air-dried whole plants of E. stracheyi (7.0 kg) with methanol three times at room temperature and then combining to concentrate in vacuo. The extract was suspended in water and further extracted sequentially with petroleum ether and ethyl acetate to afford the 700 g ethyl acetate fraction by evaporation. The obtained ethyl acetate extract was then chromatographed on a silica gel column and eluted successively with a gradient of petroleum ether/ethyl acetate (100:0 to 0:100, v/v) to provide 8 fractions, F1−F8, in which F4, F5, and F6 were further separated due to the richness of compounds in our analysis. Fraction F4 (43 g) was chromatographed on an MCI gel column and eluted with MeOH/H2O (40:60 to 100:0, v/v) to afford fractions F4.1–F4.7. The resulting fraction F4.5 (6.3 g) was chromatographed on a Sephadex LH-20 column (MeOH/MeCl3, 1:1, v/v) to yield three fractions, F4.5.1–F4.5.3. Silica gel column chromatography was used to separate the F4.5.3 fraction (3.6 g) by eluting with a gradient of ether/ethyl acetate (20:1 to 1:1, v/v) to give 12 subfractions. Subfraction F4.5.3.3 (96.3 mg) was subjected to preparative HPLC separation (CH3CN/H2O, 70:30, v/v 3 mL/min) to yield compound 2 (tR = 23.6 min, 4.1 mg). Fraction F4.5.3.10 (605 mg) was purified by preparative HPLC separation (CH3CN/H2O, 70:30, v/v 3 mL/min) to yield compound 4 (tR = 26.7 min, 8.8 mg). An MCI gel column was used with a gradient of MeOH/H2O (40:60–100:0, v/v) to separate fraction F5 (53 g), which led to 12 fractions. F5.8 (6.5 g) was further purified by silica gel column chromatography and eluted with an ether/ethyl acetate gradient of (20:1–1:1, v/v) to afford 6 fractions, F5.8.1–F5.8.6. The obtained fraction F5.8.2 (1.5 g) was separated by a Sephadex LH-20 column (MeOH/MeCl3 1:1, v/v) to afford 4 fractions. Fraction F5.5.2.4 (29.3 mg) was subjected to preparative HPLC separation with gradients of 82:18 (CH3CN/H2O, v/v 3 mL/min) to yield compound 3 (tR = 26.7 min, 5.7 mg). Fraction F6 (61 g) was loaded onto an MCI gel column with a MeOH/H2O gradient of (40:60–100:0, v/v), resulting in 10 fractions, in which fraction F4.7 was found to be pure compound 1 (17.8 mg). Fraction F6.6 (10 g) was subjected to the silica gel column with an ether/ethyl acetate gradient of (20:1–1:1, v/v) to yield 6 fractions, in which fraction F6.5 (1.1 g) was subjected to a Sephadex LH-20 column (MeOH/MeCl3 1:1, v/v) to give 9 fractions F6.5.1–F6.6.9. Then, fraction F6.5.2 (163.0 mg) was separated by silica gel column chromatography with an ether/ethyl acetate gradient of (10:1–2:1) to yield compounds 8 (9.9 mg) and 9 (1.9 mg). The fraction F6.5.4 (0.482 g) was chromatographed on a silica gel column with an ether/ethyl acetate gradient of (20:1–1:1, v/v) to afford compounds 10 (8.5 mg) and 11 (13 mg). The fraction F6.8 (7.3 g) was separated with a Sephadex LH-20 column (MeOH/MeCl3 1:1, v/v) to give six fractions, in which fraction F6.8.3 (695 mg) was further separated by silica gel column chromatography with a ether/ethyl acetate gradient of (10:1–5:1, v/v) to afford 8 fractions. The resulting fraction F6.8.3.6 (51.1 mg) was purified by preparative HPLC (CH3CN/H2O, 60:40, v/v 3 mL/min) to give compounds 6 (tR = 14.4 min, 11.9 mg) and 7 (tR = 15.3 min, 6.9 mg). The fraction F6.8.3.7 (12.3 mg) was then purified by preparative HPLC (CH3CN/H2O, 77:23, v/v 3 mL/min) to give compound 5 (tR = 14.8 min, 11.2 mg).

2.3. X-ray Crystallographic Analyses

A light, colorless crystal of 1 was used for the X-ray crystallographic analysis on a Bruker APEX DUO diffractometer equipped with Cu Kα radiation (λ = 1.54178 Å). To solve and determine the structures and absolute configurations of 1, the ShelXT 28 program with Intrinsic Phasing was used [15].
The crystallographic data of Compound 1 is listed as follows: M = 318.44, approximate dimensions 0.800 × 0.160 × 0.110 mm3, calculated density 1.189 Mg/m3, a = 10.0464(12) Å, b = 9.5021(11) Å, c = 10.0557(12) Å, α = 90°, β = 112.043(4)°, γ = 90°, V = 889.77(18) Å3, T = 100.(2) K, space group P1211, Z = 2, 17,575 reflections measured, 3416 independent reflections (Rint = 0.0553). The final R1 values were 0.0341 (I > 2σ(I)). The final wR(F2) values were 0.0848 (I > 2σ(I)). The final R1 values were 0.0359 (all data). The final wR(F2) values were 0.0866 (all data). The goodness of fit on F2 was 1.048. Flack parameter = 0.03(9).
Crystallographic data for the structure of compound 1 have been deposited at the Cambridge Crystallographic Data Center (https://ccdc.cam.ac.uk, accessed on 9 May 2023) with the deposition number of 2258198. Copies of the above data can be obtained free of charge on application at this address: www.ccd.cam.ac.uk.

2.4. In Vitro Cytotoxic Activity Screening of Cells with HL-60, A-549, SMMC-7721, MCF-7, SW-480

Compound 1 was screened for in vitro cytotoxic activity in human promyelocytic leukemia cells (HL-60), human lung cancer cells (A-549), human liver cancer cells (SMMC-7721), human breast cancer cells (MCF-7), and human colon cancer cells (SW-480) using the MTT assay by following the below method with cisplatin (DDP) and paclitaxel (Taxol) as positive controls.
  • Cell inoculation: A single cell suspension was obtained from a culture medium (DMEM or RMPI1640) containing 10% fetal bovine serum, and 3000–15,000 cells per well were inoculated onto a 96-well flat-bottomed microtiter plate at a volume of 100 μL per well. The cells were inoculated 12–24 h in advance for culture.
  • Addition of compounds to be tested: Dimethyl sulfoxide (DMSO) solutions containing different concentrations of the tested compound (diluted from 40 μM) were added to a final volume of 200 μL per well, and three replicates were set for each group of treatments.
  • Color development: After incubation at 37 °C for 48 h, the culture solution was discarded for adherent cells, and 20 μL of MTS solution and 100 μL of culture solution were added to each well, respectively; 100 μL of culture supernatant was discarded for suspended cells and 20 μL of MTS solution was added to each well. Incubation was continued for 2~4 h. Then, to measure the light absorption values, 3 blank controls (120 μL of the mixture of MTS solution and culture solution) were set.
  • Colorimetric: A wavelength of 492 nm was selected, and the light absorption value of each well was read by MULTISKAN FC. The results were recorded, and the data were processed and plotted against the compound number as the horizontal coordinate and the cell inhibition rate as the vertical coordinate.
  • Positive control compounds: Two positive compounds, DDP and Taxol, were used in each experiment, and the cell growth curves were plotted with the concentration as the horizontal coordinate and the cell survival rate as the vertical coordinate.
Metabolites 13 00852 g001 550
Figure 1. Structures of isolated compounds from E. stracheyi.
Figure 1. Structures of isolated compounds from E. stracheyi.
Metabolites 13 00852 g001

3. Results

3.1. Structure Identification

Compound 1 was isolated as colorless massive crystals (methanol). Its molecular formula was defined as C20H30O3 by its positive HRESIMS spectrum, which showed a sodium adduct ion peak at m/z 341.2083 [M + Na]+, giving the molecular formula C20H30O3Na calculated as 341.2093, and six degrees of unsaturation. The IR spectrum showed absorption bands at 3434, 1682, and 1631 cm−1, which indicate the presence of hydroxyl and carbonyl functionalities. The 1H NMR spectrum of compound 1 showed two double-peaked methyl signals at δH 0.99 (3H, d, J = 7.0 Hz) and 1.23 (3H, d, J = 7.0 Hz), a broad double-peaked methyl signal at δH 1.53 (3H, br d), two single-peaked methyl signals at δH 0.81 (3H, s) and 1.08 (3H, s), two oxymethine protons at δH 4.40 (1H, d, J = 5.5 Hz) and 4.94 (1H, t, J = 5.0 Hz), an exchangeable proton at δH 1.61 (1H, d, J = 5.0 Hz), and a tridisubstituted double bond at δH 6.05 (1H, s). The 13C NMR data (Table 1) showed 20 carbons, including five methyls [δC 14.9, 15.7, 16.4, 17.8, and 29.1], three methylenes [δC 26.4, 29.0 and 35.5], seven methines (including one sp2 hybrid methine at δC 114.6, two oxygen-linked methines at δC 70.9 and 73.1, and four others at δC 20.0, 22.6, 37.1, and 39.9), and five quaternary carbons (including three sp2 hybrid quaternary carbons at δC 136.7, 145.3, and 177.4, one carbonyl group at δC 210.1, and one sp3 hybrid quaternary carbon at δC 16.2), which suggests a typical lathyrane-type diterpene with a 5/11/3-membered ring system [16].
The planar structure of compound 1 was determined through careful analysis of its 2D NMR data. The HMBC spectrum of 1 showed correlations of H-1 (δH 2.44, 2.91) to C-2 (δC 39.9), C-3 (δC 210.1), C-4 (δC 136.7), C-15 (δC 177.4), and C-16 (δC 16.4); and H-2 (δH 2.46) to C-1 (δC 35.5) and C-3. These data, together with the 1H-1H COSY cross-peak correlations of H2-1/H-2 and H-2/H3-16 (δH 1.23), indicated the existence of a five-membered ring A consisting of C-1, C-2, C-3, C-4, and C-15. The downfield-shifted carbon signals of the α, β-unsaturated ketone (δC 210.1, 177.4, 136.7) further confirmed the presence of this five-membered ring involving C-3, C-4, and C-15. Furthermore, the 1H-1H COSY spectrum of 1 gave successive H-7 (δH 4.40)/H-8 (δH 2.12, 1.01)/H-9 (δH 0.93)/H-11 (δH 0.49)/H-12 (δH 1.37, 1.02)/H-13 (δH 1.98)/H3-20 (δH 0.99) correlations. The HMBC cross-peaks of H-5 (δH 6.05) to C-6 (δC 145.3), C-7 (δC 73.1), C-15, and C-17 (δC 17.8), as well as H-14 (δH 4.94) to C-15, linked the above structure fragment to C-5, C-6, and C-15 to afford ring B. The presence of the C ring was determined by correlation of two methine methyls, H3-18 (δH 1.08) and H3-19 (δH 0.81), with two methines, C-9 (δC 20.0) and C-11 (δC 22.6), and one quaternary carbon, C-10 (δC 16.2), respectively, in the HMBC spectrum. The 1H-1H COSY correlation of OH-14 (δH 1.61) with C-14 (δC 70.9) determined the location of this hydroxyl group, while another hydroxyl group was assigned at C-7 (δC 73.1) by its chemical shift of δC 73.1, albeit in the absence of resonances for the hydroxyl group.
The relative conformation of compound 1 was determined by the ROESY experiments, which showed the following correlation signals (Figure 2): H-14 (δH 4.94)/H-11 (δH 0.49), H-11/H-9 (δH 0.93), H-11/H3-20 (δH 0.99), H-14/H-5 (δH 6.05), H-11/H3-18 (δH 1.08), and H-9 (δH 0.93)/H3-18. These data suggested that H-14, H3-20, H-9, H-11, and H3-18 are cofacial and assigned as α-oriented and determined the β-configurations of H-13 and OH-14 simultaneously. The ROESY cross-peaks of H-13 (δH 1.98)/H-1β (δH 2.91) and H-1β/H-2 (δH 2.46) determined H-2 as a β-configuration and H3-16 as an α-configuration. However, the H-7 (δH 4.40)/H3-17 (δH 1.53) cross-peaks were insufficient to determine their conformations. Fortunately, the crystals of compound 1 were obtained, which confirmed the correctness of the relative conformation determined by the ROESY spectrum described above and assigned H-7 as a β-configuration and OH-7 as an α-configuration. Interestingly, although the planar structures of compound 1, kansuingols A and B, are quite similar, there are many differences in their relative conformations, that is, methyl-16, methyl-20, and hydroxyl-7 of compound 1 are α-oriented, while the corresponding groups of kansuingols A and B are β-oriented [17]. Finally, the Flack parameter value of the crystal structure of compound 1 was 0.03(9), which led to the determination of its absolute configuration, as shown in Figure 3.
Furthermore, based on the comparison of the NMR data with those reported in the literature, the known compounds euphopepluanones D (2) [18], 5-O-benzoyl-20-deoxymgenol (3) [19], 3-O-benzoyl-20-deoxymgenol (4) [19], ingenol-20-angelate (5) [20], helioscopinolide A (6) [21], 7α-hydroxy-8α,14-dihydro jolkinolide E (7) [22], 5,6-epoxy-3-hydroxy-7-megastigmen-9-one (8) [23], PBI 344 (9) [24], kaempferol (10) [25], and naringenin (11) [26] were identified.

3.2. Cytotoxicity

The isolated compounds were screened and evaluated for their cytotoxicities against five human cancer cell lines (namely, human promyelocytic Leukemia cells HL-60, human lung cancer cells A-549, human liver cancer cells SMMC-7721, human breast cancer cells MCF-7, and human colon cancer cells SW480), with DDP and Taxol as two positive controls. Only compound 4 showed moderated cytotoxic activity against HL-60, A-549, SMMC-7721, MCF-7, and SW480 cell lines, with IC50 values of 10.5 ± 0.18, 21.47 ± 0.17, 18.36 ± 1.17, 18.82 ± 0.84, and 16.25 ± 0.71 μM, respectively; while DDP has IC50 values of 10.28 ± 0.21, 29.70 ± 0.72, 13.66 ± 0.76, 27.28 ± 1.23, and 24.13 ± 1.09; Taxol has IC50 values of <0.008, 0.127 ± 0.007, <0.008, <0.008, and <0.008, respectively. The other compounds were inactive at a concentration of 40 μM.

4. Discussion

Euphorbia plants are known for their irritant milky latex [27] and characteristic and chemically diverse diterpenoids. Among the macrocyclic and polycyclic diterpenoids from Euphorbia, jatrophane types are the most common [28,29,30,31]. To date, the diterpenoids reported from E. stracheyi have included ent-kaurane, ent-abietane, ent-atisane, ent-isopimarane, labdane, tigliane, lathyrane, and ingenane-type diterpenoids [10,11,12,13,14], but no jatrophanes were isolated from the species. In the present study, besides the new compound euphostrachenol A, one lathyrane-type, three ingenane-type, and two abietane-type diterpenoids were isolated from E. stracheyi, all of which are known compounds and were discovered from other species of Euphorbia, suggesting a similar diterpenoid profile of these species. Importantly, our phytochemical investigation of E. stracheyi reported here also yielded no jatrophane-type diterpenoids, in accordance with the previous results. This type of diterpenoid is found exclusively in the Euphorbiaceae family, and it has a 5/12 bicyclic pentadecane skeleton, in which the absence of a cyclopropane ring is the most obvious structural feature that differentiates it from other macrocyclic and polycyclic diterpenoids from Euphorbia, such as tigliane, lathyrane, and ingenane types. The absence of jatrophanes in the species may be related to the special environment in which E. stracheyi lives, namely, the high-altitude region, which is often associated with high loads of UV radiation and low temperatures. Jatrophane-type diterpenoids exhibit many different activities, including antitumor, antiviral, antifungal, and anti-inflammatory effects [2,3]. Many of them showed promising P-glycoprotein, a membrane protein that pumps anticancer drugs out of cells, exhibits inhibitor activity, and could be developed as a new drug to reverse multidrug resistance [2,3]. Thus, the pharmacological value of E. stracheyi may be influenced. Furthermore, the lack of jatrophanes implied that its biosynthetic pathway may be lost in the plant of E. stracheyi. Currently, jatrophanes were suggested to be derived from lathyrane-type diterpenoids by combined transcriptomic, genomic, and metabolomic investigation of E. peplus, a species harboring many jatrophane-type diterpenoids [32]. Thus, comparative genomic and transcriptomic analysis between these two species could provide useful clues for uncovering the biosynthesis of jatrophane-type diterpenoids.
Notably, ionones are rarely isolated from the species of Euphorbia [2]; however, they were reported constituents of E. stracheyi [8,12]. We also reported two ionones from E. stracheyi, in agreement with previous studies. Ionones are degraded from carotenoids that play an important role in helping plants adapt to high UV light and low temperatures. During photosynthesis, carotenoids are known to protect chlorophylls and bacteriochlorophylls from sensitizing deleterious photodestructive reactions [33]. The detection of ionones in E. stracheyi in the present and previous studies strongly suggested that this type of secondary metabolite should be the result of high-altitude adaptation of the species. Further work should be undertaken to reveal whether other Euphorbia plants adapted to the harsh environments of Tibetan peaches also harbor ionones.
Notably, the planar structure of compound 1 shows high similarity to those of kansuingols A and B, except for a β–D-glucose group and a hydroxyl group present at C-15 and C-19 of kansuingol A, as well as a β–D-glucose group at C-19 of kansuingol B, respectively [17]. Notably, the relative conformations of these three compounds are also different for methyl-16, methyl-20, and hydroxyl-7. While the relative conformations of compound 1 were supported by X-ray diffraction analysis, those of kansuingols A and B were not. After checking the key ROESY correlations that determined the relative conformation assignment of methyl-16, methyl-20, and hydroxyl-7 in kansuingols A and B, we found that there are no ROESY correlations to support the claimed β-orientation of methyl-16 in both compounds. Therefore, the structures of kansuingols A and B remain to be determined.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/metabo13070852/s1, Figures S1–S31: Spectrums of compounds 1–11; Table S1: Crystal data and structure refinement for compound 1. Table S2: Cytotoxicity data of compounds 1–11 at the concentration of 40 μM.

Author Contributions

Conceptualization, L.Y.; methodology, H.Z., X.R. and Y.H.; software, H.Z. and X.R.; formal analysis, L.Y., H.Z. and X.R.; data curation, H.Z. and X.R.; writing—original draft preparation, H.Z. and X.R.; writing—review and editing, L.Y. and T.S.; All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the Yunnan Revitalization Talent Support Program “Top Team” Project (number 202305AT350001), the Open Fund of Shanghai Key Laboratory of Plant Functional Genomics and Resources under Grant (number PFGR202201), the National Natural Science Foundation of China (Grant No. 32070338), the Special Fund for Shanghai Landscaping Administration Bureau Program (Grant No. 222414), and the Ministry of Science and Technology of the People’s Republic of China (Grant No. YDZX20223100001003).

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Informed consent was obtained from all subjects involved in the study.

Data Availability Statement

The data presented in this study are available in the main article and the Supplementary Materials.

Acknowledgments

We thank Yu Kong and Jing-Jing Xu for their generous help with this work.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Ernst, M.; Grace, O.M.; Saslis-Lagoudakis, C.H.; Nilsson, N.; Simonsen, H.T.; Rønsted, N. Global medicinal uses of Euphorbia L. (Euphorbiaceae). J. Ethnopharmacol. 2015, 176, 90–101. [Google Scholar] [CrossRef] [PubMed]
  2. Shi, Q.W.; Su, X.H.; Kiyota, H. Chemical and pharmacological research of the plants in genus Euphorbia. Chem. Rev. 2008, 108, 4295–4327. [Google Scholar] [CrossRef] [PubMed]
  3. Vasas, A.; Hohmann, J. Euphorbia diterpenes: Isolation, structure, biological activity, and synthesis (2008–2012). Chem. Rev. 2014, 114, 8579–8612. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  4. Vasas, A.; Rédei, D.; Csupor, D.; Molnár, J.; Hohmann, J. Diterpenes from European Euphorbia species serving as prototypes for natural-product-based drug discovery. Eur. J. Org. Chem. 2012, 2012, 5115–5130. [Google Scholar] [CrossRef]
  5. Li, C.Y.; Yang, L.; Liu, Y.; Xu, Z.G.; Gao, J.; Huang, Y.B.; Xu, J.J.; Fan, H.; Kong, Y.; Wei, Y.K.; et al. The sage genome provides insight into the evolutionary dynamics of diterpene biosynthesis gene cluster in plants. Cell Rep. 2022, 40, 111236. [Google Scholar] [CrossRef]
  6. Song, J.J.; Fang, X.; Li, C.Y.; Jiang, Y.; Li, J.X.; Wu, S.; Guo, J.; Liu, Y.; Fan, H.; Huang, Y.B.; et al. A 2-oxoglutarate-dependent dioxygenase converts dihydrofuran to furan in Salvia diterpenoids. Plant Physiol. 2022, 188, 1496–1506. [Google Scholar] [CrossRef]
  7. Editorial Committee of the Flora of China, Chinese Academy of Sciences. Flora of China; Science Press: Beijing, China, 1997. [Google Scholar]
  8. Zhang, B.Y.; Wang, H.; Luo, X.D.; Du, Z.Z.; Shen, J.W.; Zeng, L.F.; Zhang, X.F. Chemical constituents from Euphorbia stracheyi. Chin. Tradit. Herb. Drugs 2012, 43, 1496–1498. [Google Scholar]
  9. Ma, Z.k.; Dai, Y.; Zhang, B.B.; Liao, Z.X. Study on chemical constituents of Euphorbia stracheyi Boiss. Northwest Pharm. J. 2012, 27, 1–4. [Google Scholar]
  10. Yang, D.S.; Peng, W.B.; Li, Z.L.; Wang, X.; Wei, J.G.; He, Q.X.; Yang, Y.P.; Liu, K.C.; Li, X.L. Chemical constituents from Euphorbia stracheyi and their biological activities. Fitoterapia 2014, 97, 211–218. [Google Scholar] [CrossRef]
  11. Liu, T.; Liang, Q.; Xiong, N.N.; Dai, L.F.; Wang, J.M.; Ji, X.H.; Xu, W.H. A new ent-kaurane diterpene from Euphorbia sttacheyi Boiss. Nat. Prod. Res. 2017, 31, 233–238. [Google Scholar] [CrossRef]
  12. Liu, T.; Liang, Q.; Zhang, X.M.; Su, X.M.; Qin, J.C.; Li, G.Q.; Xu, W.H. Chemical constituents from Euphorbia stracheyi Boiss. Biochem. Syst. Ecol. 2019, 84, 52–54. [Google Scholar] [CrossRef]
  13. Ye, Y.; Liu, G.H.; Dawa, D.; Ding, L.S.; Cao, Z.X.; Zhou, Y. Cytotoxic diterpenoids from the roots of Euphorbia stracheyi. Phytochem. Lett. 2020, 36, 183–187. [Google Scholar] [CrossRef]
  14. Yuan, F.Y.; Pan, Y.H.; Yin, A.P.; Li, W.; Huang, D.; Yan, X.L.; Wu, S.Q.; Tang, G.H.; Pu, R.; Yin, S. Euphorstranoids A and B, two highly rearranged ingenane diterpenoids from Euphorbia stracheyi: Structural elucidation, chemical transformation, and lipid-lowering activity. Org. Chem. Front. 2022, 9, 775–780. [Google Scholar] [CrossRef]
  15. Su, J.C.; Cheng, W.; Song, J.G.; Zong, Y.L.; Huang, X.J.; Jiang, R.W.; Li, Y.L.; Li, M.M.; Ye, W.C.; Wang, Y. Macrocyclic diterpenoids form Euphorbia helioscopia and their potential anti-inflammatory activity. J. Nat. Prod. 2019, 82, 2818–2827. [Google Scholar] [CrossRef]
  16. Adolf, W.; KÖhler, I.; Hecker, E. Lathyrane type diterpene esters from Euphorbia lathyris. Phytochemistry 1984, 23, 1461–1463. [Google Scholar] [CrossRef]
  17. Kim, Y.M.; Ahn, J.; Chae, H.S.; Choi, Y.H.; Kim, J.; Chin, Y.-W. Two new lathyrane-type diterpenoid glycosides with IL-6 production inhibitory activity from the roots of Euphorbia kansui. Bioorg. Med. Chem. Lett. 2018, 28, 1207–1210. [Google Scholar] [CrossRef] [PubMed]
  18. Chen, Y.N.; Ding, X.; Lu, Q.Y.; Li, D.M.; Li, B.T.; Liu, S.; Yang, L.; Zhang, Y.; Di, Y.T.; Fang, X.; et al. Macrocyclic diterpenoids from the seeds of Euphorbia peplus with potential activity in inducing lysosomal biogenesis. Bioorg. Chem. 2020, 105, 104464. [Google Scholar] [CrossRef]
  19. Zhang, L.; Gao, L.; Li, Z.J.; Yan, X.J.; Yang, Y.J.; Tang, Y.P.; Cao, Y.D.; Ding, A.W. Bio-Guided isolation of the cytotoxic terpenoids from the roots of Euphorbia kansui against human normal cell lines L-O2 and GES-1. Int. J. Mol. Sci. 2012, 13, 11247–11259. [Google Scholar] [CrossRef] [Green Version]
  20. Teng, R.-W.; McManus, D.; Aylward, J.; Ogbouren, S.; Armstrong, D.; Mau, S.-L.; Johns, J.; Bacic, A. Biotransformation of ingenol-3-angelate in four plant cell suspension cultures. Biocatal. Biotransform. 2009, 27, 186–194. [Google Scholar] [CrossRef]
  21. Borghi, D.; Baumer, L.; Ballabio, M.; Arlandini, E.; Perellino, N.C.; Minghetti, A.; Vincieri, F.F. Structure elucidation of Helioscopinolide-D and Helioscopinolide-E from Euphorbia calyptrata cell cultures. J. Nat. Prod. 1991, 54, 1503–1508. [Google Scholar] [CrossRef]
  22. Chen, Y.N.; Lu, Q.Y.; Li, D.M.; Li, Y.Y.; Pu, X.X.; Li, B.T.; Tang, X.H.; Tang, H.Y.; Liu, S.; Yang, L.; et al. Three new diterpenoids from Euphorbia peplus. Nat. Prod. Res. 2021, 35, 3901–3907. [Google Scholar] [CrossRef] [PubMed]
  23. Kim, K.H.; Lee, K.H.; Choi, S.U.; Kim, Y.H.; Lee, K.R. Terpene and phenolic constituents of Lactuca indica L. Arch. Pharmacal Res. 2008, 31, 983–988. [Google Scholar] [CrossRef] [PubMed]
  24. Fuchs, E.E.; Livingston, N.J.; Abrams, S.R.; Rose, P.A. Structure-activity relationships of ABA analogs based on their effects on the gas exchange of clonal white spruce (Picea glauca) emblings. Physiol. Plant. 1999, 105, 246–256. [Google Scholar] [CrossRef]
  25. Itoh, T.; Ninomiya, M.; Yasuda, M.; Koshikawa, K.; Deyashiki, Y.; Nozawa, Y.; Akao, Y.; Koketsu, M. Inhibitory effects of flavonoids isolated from Fragaria ananassa Duch on IgE-mediated degranulation in rat basophilic leukemia RBL-2H3. Bioorg. Med. Chem. 2009, 17, 5374–5379. [Google Scholar] [CrossRef] [PubMed]
  26. Jeon, S.H.; Chun, W.; Choi, Y.J.; Kwon, Y.S. Cytotoxic constituents from the bark of Salix hulteni. Arch. Pharmacal Res. 2008, 31, 978–982. [Google Scholar] [CrossRef]
  27. Horn, J.W.; van Ee, B.W.; Morawetz, J.J.; Riina, R.; Steinmann, V.W.; Berry, P.E.; Wurdack, K.J. Phylogenetics and the evolution of major structural characters in the giant genus Euphorbia L. (Euphorbiaceae). Mol. Phylogenet. Evol. 2012, 63, 305–326. [Google Scholar] [CrossRef]
  28. Appendino, G.; Jakupovic, S.; Tron, G.C.; Jakupovic, J.; Milon, V.; Ballero, M. Macrocyclic diterpenoids from Euporbia semiperfoliata. J. Nat. Prod. 1998, 61, 749–756. [Google Scholar] [CrossRef]
  29. Fattahian, M.; Ghanadian, M.; Ali, Z.; Khan, I.A. Jatrophane and rearranged jatrophane-type diterpenes: Biogenesis, structure, isolation, biological activity and SARs (1984–2019). Phytochem. Rev. 2020, 19, 265–336. [Google Scholar] [CrossRef]
  30. Yang, Y.; Zhou, M.; Wang, D.; Liu, X.; Ye, X.; Wang, G.; Lin, T.; Sun, C.; Ding, R.; Tian, W.; et al. Jatrophane Diterpenoids from Euphorbia peplus as Multidrug Resistance Modulators with Inhibitory Effects on the ATR-Chk-1 Pathway. J. Nat. Prod. 2021, 84, 339–351. [Google Scholar] [CrossRef]
  31. Chen, Y.N.; Ding, X.; Li, D.M.; Lu, Q.Y.; Liu, S.; Li, Y.Y.; Di, Y.T.; Fang, X.; Hao, X.J. Jatrophane diterpenoids from the seeds of Euphorbia peplus with potential bioactivities in lysosomal-autophagy pathway. Nat. Prod. Bioprospect. 2021, 11, 357–364. [Google Scholar] [CrossRef]
  32. Czechowski, T.; Forestier, E.; Swamidatta, S.H.; Gilday, A.D.; Cording, A.; Larson, T.R.; Harvey, D.; Li, Y.; He, Z.; King, A.J.; et al. Gene discovery and virus-induced gene silencing reveal branched pathways to major classes of bioactive diterpenoids in Euphorbia peplus. Proc. Natl. Acad. Sci. USA 2022, 119, e2203890119. [Google Scholar] [CrossRef] [PubMed]
  33. Avalos, J.; Carmen, L.M. Biological roles of fungal carotenoids. Curr. Genet. 2015, 61, 309–324. [Google Scholar] [CrossRef] [PubMed]
Metabolites 13 00852 g002 550
Figure 2. 1H-1H COSY (—), key HMBC (⟶), and ROESY (⟷) correlations of compound 1.
Figure 2. 1H-1H COSY (—), key HMBC (⟶), and ROESY (⟷) correlations of compound 1.
Metabolites 13 00852 g002
Metabolites 13 00852 g003 550
Figure 3. ORTEP drawing of compound 1.
Figure 3. ORTEP drawing of compound 1.
Metabolites 13 00852 g003
Table
Table 1. NMR data of compound 1 (500 MHz for 1H/and 125 MHz for 13C, CDCl3).
Table 1. NMR data of compound 1 (500 MHz for 1H/and 125 MHz for 13C, CDCl3).
Carbon PositionδHδCCarbon PositionδHδC
1α2.44 (1H, m)35.5110.49 (1H, ddd, J = 12.5, 7.5, 5.0 Hz)22.6
1β2.91 (1H, m) 12α1.37 (1H, ddd, J = 12.5, 7.5, 5.0 Hz)26.4
22.46 (1H, m)39.912β1.02 (1H, m)
3 210.1131.98 (1H, m)37.1
4 136.7144.94 (1H, t, J = 5.0 Hz)70.9
56.05 (1H, s)114.615 177.4
6 145.3161.23 (3H, d, J = 7.0 Hz)16.4
74.40 (1H, d, J = 5.5 Hz)73.1171.53 (3H, br d)17.8
8α2.12 (1H, ddd, J = 14.5, 5.5, 1.0 Hz)29.0181.08 (3H, s)29.1
8β1.01 (1H, m) 190.81 (3H, s)15.7
90.93 (1H, m)20.0200.99 (3H, d, J = 7.0 Hz)14.9
10 16.214-OH1.61 (1H, d, J = 5.0 Hz)
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Zhu, H.; Ren, X.; Huang, Y.; Su, T.; Yang, L. Chemical Constituents of Euphorbia stracheyi Boiss (Euphorbiaceae). Metabolites 2023, 13, 852. https://doi.org/10.3390/metabo13070852

AMA Style

Zhu H, Ren X, Huang Y, Su T, Yang L. Chemical Constituents of Euphorbia stracheyi Boiss (Euphorbiaceae). Metabolites. 2023; 13(7):852. https://doi.org/10.3390/metabo13070852

Chicago/Turabian Style

Zhu, Hui, Xiangxiang Ren, Yanbo Huang, Tao Su, and Lei Yang. 2023. "Chemical Constituents of Euphorbia stracheyi Boiss (Euphorbiaceae)" Metabolites 13, no. 7: 852. https://doi.org/10.3390/metabo13070852

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop