Euphraticanoids N–T: Aromadendrane-Type Diterpenes and Sesquiterpenes with Fungicidal Activities from Populus euphratica Resins
1
School of Pharmacy, Guangdong Pharmaceutical University, Guangzhou 510006, China
2
Guangdong Provincial Key Laboratory of Chinese Medicine Ingredients and Gut Microbiomics, Institute for Inheritance-Based Innovation of Chinese Medicine, School of Pharmacy, Shenzhen University, Shenzhen 518055, China
*
Author to whom correspondence should be addressed.
†
These authors contributed equally to this work.
Int. J. Mol. Sci. 2025, 26(5), 2187; https://doi.org/10.3390/ijms26052187
Submission received: 16 February 2025
/
Revised: 25 February 2025
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Accepted: 26 February 2025
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Published: 28 February 2025
(This article belongs to the Topic Research on Natural Bioactive Product-Based Pesticidal Agents—2nd Edition)
Abstract
Seven previously undescribed terpenoids, including five prenylaromadendrane-type diterpenes euphraticanoids N–R (1–5) and two aromadendrane-type sesquiterpenes, euphraticanoids S and T (6 and 7), were isolated from Populus euphratica resins. Their structures, including their absolute configurations, were elucidated by HRESIMS and spectroscopic analysis, ECD calculations, and crystallographic methods. In addition, an evaluation of the fungicidal activities of compound 1 was carried out, resulting in the discovery of 1 as a fungicidal candidate lead compound with an EC50 of 15.7 and 68.6 mg/L against Curvularia mebaldsii and Fusarium graminearum, respectively.
1. Introduction
All living creatures, including humans, animals, and plants, have developed diverse defense strategies though evolution for self-protection, as they face extreme stresses such as environmental stresses and social stresses. Among various defense mechanisms, exudate production plays an important role. For example, humans shed tears when they get hurt; the hagfish produces slime when it is provoked [1]; sperm whales create ambergris when they eat hard squid beak chitin, an irritant [2]; and Megaponera analisantis ants secrete saliva to treat infected wounds when nestmates are infected [3]. However, the phenomenon of resinous exudate production to defend against injury is more common in plants than humans and animals, such as agarwood from the resinous heartwood of Aquilaria tree [4]; red resin from the fruits of Daemonorops draco tree [5]; yellowish resins from Ferula sinkiangensis [6], and so on. We assumed that these plants’ resinous exudates are used to defend, and should have biological activities, which also suggested that these resins may be a potentially valuable reservoir in drug discovery. Therefore, our group has focused on plant resins in recent years. A recent comprehensive review by us summarized the chemistry and biological activity of recent substances, highlighting our contribution to this field [7]. The tears of Populus euphratica were collected for systematic research by us, accompanied by discovering a series of structurally intriguing and biologically significant compounds, including various terpenoids [8]. As a continuous study on this topic, five prenylaromadendrane-type diterpenes euphraticanoids N–R (1–5) and two aromadendrane-type sesquiterpenes euphraticanoids S and T (6 and 7) were identified (Figure 1). In addition, we evaluated the fungicidal activity of compounds 1–7. As a result, compound 1 was found to exhibit potent fungicidal activity against Curvularia mebaldsii and Fusarium graminearum. This finding provides hope for the discovery of fungicides derived from P. euphratica.
2. Results and Discussion
2.1. Compound Structure Elucidation
Euphraticanoid N (1) was obtained as yellowish crystals through crystallization of methanol, and its molecular formula C20H30O2 was supported by HRESIMS (m/z 303.2311 [M + H]+, calcd for C20H31O2, 303.2319), 13C NMR, and DEPT spectra. The 1H NMR spectrum (Table 1) showed signals for four methyl groups at δH 2.14 (3H, d, J = 0.8 Hz), 1.87 (3H, d, J = 0.8 Hz), 1.24 (3H, s), and 1.03 (3H, s), and three olefinic protons at δH 6.00 (1H, brs), 4.73 (1H, brs), and 4.69 (1H, brs), along with two characteristic protons at δH 0.60 (1H, t-like, J = 11.0 Hz) and 0.77 (1H, td, J = 11.0, 6.6 Hz). According to the 13C NMR and DEPT spectra (Table 2), there were twenty distinct carbon resonances, categorized into four methyl groups, six methylene groups, five methine groups, and five signals from nonprotonated carbons (one ketocarbonyl group at δC 201.0, two olefinic groups at δC 155.8 and 154.3, one oxygenated group at δC 79.8, and one sp3 quaternary carbon). The data mentioned above indicated that compound 1 is a prenylaromadendrane-type diterpene, and 1D NMR data analysis suggested that the signals of 1 were similar to those of 4β-hydroxy-15-(3-methyl-2-butenyl) aromadendr-Δ10(12)-en [9]. In the 13C NMR spectrum, a key difference was that the methylene singlet at δC 25.6 (C-16) was substituted by a ketone carbonyl signal at δC 201.0, along with a downfield shift in C-15 (δC 39.1→δC 56.6) and C-18 (δC 131.2→δC 155.8) carbon signals adjacent to C-16. Furthermore, the specific UV absorption wavelength (239 nm) combined with the molecular weight of 1 suggested that the methylene at C-16 was transformed into a ketone carbonyl, forming an α,β-unsaturated ketone carbonyl group with the double bond between C-17 and C-18. The conclusion also was further supported by the HMBC correlations (Figure 2) of H2-15/C-16 (δC 201.1), C-17 (δC 124.1), and H3-19/C-17, C-18 (δC 155.8). As a result, the planar structure of 1 was determined (Figure 1).
To establish the relative configuration of 1, a ROESY experiment was conducted. The ROESY correlations (Figure 3) between H-7/Ha-15, H-1 (weak), H-6/Ha-15, H-1, H3-11, and H3-14/H-5 implied that H-6, H-7, H-1, CH3-11, and H2-15 were on the same face and β-oriented, while CH3-14 and H-5 were α-oriented. The absolute configuration of compound 1 was identified through electronic circular dichroism (ECD) calculations at the B3LYP/6-311g(d,p) level. The data demonstrated that the ECD spectrum calculated for (1S,4R,5S,6S,7S,13R)-1 (Figure 4) were very similar to the experimental spectrum, confirming the absolute configuration of 1 as 1S,4R,5S,6S,7S,13R. Luckily, a suitable crystal of 1 was acquired, and X-ray diffraction analysis with CuKα radiation was performed (Figure 4), confirming the previous conclusion.
Euphraticanoid O (2) was isolated as a colorless gum, with a molecular formula of C21H34O2, determined from the HRESIMS ion peak at m/z 341.2452 [M + H]+ (calcd for C21H35O2, 341.2451). According to the 1H and 13C NMR data (Table 1 and Table 2), compound 2 resembled boscartol C [10], except for a methoxyl group resonating at δH/δC 3.19/50.5 (CH3-21) in pyridine-d5 instead of the hydroxy group. This was corroborated by the HMBC correlations (Figure 2) of H3-21/C-18 (δC 75.2), H3-18/C-17, C-18, and H3-19/C-17, C-18. Additionally, compound 2 shared the same relative configurations at the chiral centers in C-1, C-4, C-5, C-6, C-7, and C-13 as 1, based on similar findings in the 1D NMR (Table 1 and Table 2) and ROESY spectra (Figure 3). Moreover, the large coupling constant of H-17 (J = 15.7 Hz) indicated that the double bond between H-16 and H-17 is an E configuration. Finally, the absolute configuration of 2 as 1S,4R,5S,6S,7S,13R was validated through the comparison of the experimental and calculated ECD curves (Figure 4).
Euphraticanoid P (3) was identified with a molecular formula of C21H34O2, derived from the positive HRESIMS data. In the 1H and 13C NMR data (Table 1 and Table 2) for compound 3, there were strong resemblances to compound 1, with the exception of the missing ketone resonance at δC 201.0 (C-16). Instead, oxymethine signals were detected at δH/δC 4.14/75.7 (CH-16) in CDCl3 in the 1D NMR spectra of 3. Furthermore, more shielded resonances of protons for Ha-15 (δH 2.83→δH 1.52), Hb-15 (δH 1.95→δH 1.25), and H-17 (δH 6.00→δH 4.95), and carbons for C-15 (δC 56.6→δC 48.8) and C-18 (δC 155.8→δC 135.7) in CDCl3 were observed due to the conversion from a ketone carbonyl to an methoxyl group at C-16, as confirmed by the 1H-1H COSY correlations (Figure 2) of H2-15/H-16/H-17 and the HMBC correlations (Figure 2) of H3-21/C-16. Then, based on ROESY correlations and 1D NMR data similar to those of 1 and 2, the relative configuration of 1S*,4R*,5S*,6S*,7S*,13R* in 3 was identified. The relative configuration of C-16 was not assigned because the flexible side chain at C-16 poses a significant challenge. Ultimately, the absolute configuration of compound 3 was identified as 1S,4R,5S,6S,7S,13R by comparing the experimental CD curve with the calculated ECD curve (Figure 4).
Euphraticanoid Q (4) was isolated as a colorless gum and had the same molecular formula as 3, as determined by HRESIMS analysis. Detailed analysis of the 1D NMR spectra revealed that the 13C NMR data for 4 match those of 3. However, the 1H NMR data showed slight differences, such as (A) variations in the chemical shift, primarily at H-6 (δH 0.79→δC 0.94), Ha-15 (δH 2.02→δC 1.63), Hb-15 (δH 1.27→δC 1.57), and H-17 (δH 5.14→δC 5.20), and (B) changes in the splitting pattern of oxymethine proton at δH 4.21 from dt (J = 9.4, 6.6) to td (J = 8.4, 6.6 Hz), indicating that 4 was the C-16-epimer of 3. Furthermore, the conclusion was reinforced by identical ROESY correlations (Figure 3) involving H-6/H-1, Hb-15, H3-11, H-7/H-1 (weak), Hb-15, and H-5/Hb-8, H3-14, 4-OH, and the experimental ECD spectrum in 4 the same as 3.
Euphraticanoid R (5) was isolated as a colorless gum with a molecular formula of C20H32O2, as revealed by HRESIMS. The primary characteristics of the 1D NMR spectra (Table 2 and Table 3) for compound 5 was similar to those for compound 2, except that the hydroxy group signal at C-4 was absent and a hydroxymethyl group (δH 3.98, d, J = 10.4 Hz and 3.93, d, J = 10.4 Hz; δC 71.5) appeared at C-20 in the place of a methyl group. These modifications were verified by the change in splitting pattern of the methyl group at C-4 from s to d (J = 8.6 Hz) and the HMBC correlations (Figure 2) involving H3-11/C-3, C-4, C-5 and H2-20/C-17 (δC 138.7), C-18 (δC 73.6). The ROESY correlations of H-6/H-1, H3-11, H-1/H-7 (weak) and H-5/H-4, H3-14, Hb-8 were used to define its relative configuration as 1S*,4S*,5S*,6R*,7S*,13R*. In conclusion, the resemblance of the ECD curves of 5 to those of 1–4 (Figure 4) implied that the absolute configuration of 5 is 1S,4S,5S,6R,7S,13R.
Euphraticanoid S (6) was confirmed to be C16H24O3 using its HRESIMS and 13C NMR data. The 1D and 2D NMR data (Table 2 and Table 3) exhibited structural characteristics identical to those of spathulenol [9]. The primary distinction was the presence of an acetate moiety (δH/δC 2.68, 1.87/46.2; δC 176.6) at C-13, instead of a methyl group in 6, as indicated by the HMBC correlations (Figure 2) of H3-14/C-6, C-7, C-13, C-15, and H2-15/C-16 (δC 176.6). The ROESY correlations (Figure 3) involving H-6/H-1, Ha-15, H3-11, H-7/H-1 (weak), Ha-15, and H-5/H3-14 indicated that H-1, H-6, H-7, H3-11, and H2-15 were β-oriented, while H-5 and H3-14 were α-oriented. Finally, the absolute configuration of 6 was identified as 1S,4R,5S,6S,7S,13R by comparing the calculated ECD spectra with the experimental results (Figure 4).
Euphraticanoid T (7) was isolated as white solids, with a molecular formula of C15H22O3 determined through HRESIMS data. The signals in the 1H and 13C NMR spectra (Table 2 and Table 3) were almost identical to those of 6, except for the substitution of the acetate moiety at C-13 with a carboxyl group, confirmed by the HMBC correlations (Figure 2) of H-7/C-13, C-14, C-15 (δC 177.4), H-6/C-13, C-14, C-15, and H3-14/C-15. Moreover, the ROESY correlations (Figure 3) of H-1/H3-14, H-6, H-7 (weak), and H-5/H3-14 were used to determine the β-orientation of the carboxyl group. The absolute configuration was determined to be 1S,4R,5S,6S,7S,13R by comparing the calculated and experimental ECD spectra.
2.2. Biological Activity
The fungicidal activities of compounds against Fusarium graminearum, Curvularia mebaldsii, Curvularia lunata, Botrytis cinerea, Alternaria altanata, Sclerotinia sclerotiorum, and Rhizoctonia solani were evaluated, with the commercial fungicide hymexazol used as a positive control. For all compounds, preliminary screening was carried out at a concentration of 80 mg/L, and the results are shown in Table 4. It revealed that these compounds display board-spectrum fungicidal activities. In particular, compounds 1–5 show considerable fungicidal activities, which possess inhibitory rates (IRs) of over 50% towards most pathogenic fungi. Among them, compound 1 displays notable anti-C. mebaldsii with 80% IRs, whose activity far surpasses that of hymexazol. Given the sufficient quantity and attractive fungicidal activities against F. graminearum and C. mebaldsii of compounds 1 and 2 in preliminary screening, their maximal effect (EC50) values of 50% towards F. graminearum and C. mebaldsii were further measured (Figure 5 and Table 5). This demonstrated that compounds 1 and 2 possessed 15.7 and 42.1 mg/L EC50 values against C. mebaldsii, respectively, while the fungicidal levels were superior to that of hymexazol (84.8 mg/L). In addition, the EC50 values of compounds 1 (68.8 mg/L) and 2 (78.0 mg/L) against F. graminearum were close to that of hymexazol (66.3 mg/L). This finding suggested that compounds 1 and 2 could be potential alternative lead compounds for the design of fungicides.
3. Experimental Section
3.1. Fungal Material
The origin and verification of P. euphratica resins matched our previous study [6], and the voucher specimen (CHYX0573) was stored at Shenzhen University.
3.2. Extraction and Isolation
The dried resins (50.0 kg) were soaked in 95% ethanol (300 L × 3 × 24 h) to produce a crude extract, which was then mixed with water and separated using ethyl acetate. Subsequently, the EtOAc solution was concentrated under reduced pressure to produce a 12.0 kg EtOAc soluble extract. Subsequently, the extract underwent separation by multiple chromatography, obtaining compounds 1–7. For additional detailed isolation procedures, consult the Supplementary Information.
3.3. Crystal Structure of 1
The crystallographic information for euphraticanoid N (1) (deposition number CCDC 2422553) is available at the Cambridge Crystallographic Data Centre. You can access the data for free at www.ccdc.cam.ac.uk/data_request/cif (accessed on 15 February 2025), or by emailing data request@ccdc.cam.ac.uk, or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
3.4. ECD Calculations for Compounds 1–7
The main conformers of compounds 1–7 were optimized using Gaussian 09 at the B3LYP/6-311g(d,p) level. Then, we used the same method for the optimized conformers for the ECD calculations. Solvent effects were incorporated using the PCM model, with methanol serving as the solvent. The percentages of each conformation can be found in Table S3. The ECD spectra were ultimately derived from the Boltzmann-calculated contribution of each conformer.
3.5. Fungicidal Activity Assay
The fungicidal activity of compounds 1–7 was evaluated against the fungal strains using the method according to the literature [11,12,13,14]. Briefly, pathogen mycelial plugs (diameter 0.4 cm) were adhered to the center of potato dextrose agar (PDA) plates containing specific concentrations of the compounds (with equal volumes of DMSO as a control). The plates were cultivated at 26 °C for three days, and the colony diameter was measured in triplicate to assess the growth rate. The inhibition rates were identified using the formula I% = [(C − T)/(C − 0.4)] × 100%. Here, C means the diameter of fungal growth treated by DMSO; T means the diameter of fungal growth treated by the compounds; and I means the inhibition rate. An average was taken, and the standard deviation was measured.
4. Conclusions
To conclude, the current study led to the identification of five prenylaromadendrane-type diterpenes (1–5) and two aromadendrane-type sesquiterpenes (6 and 7) from P. euphratica resins. In addition, the fungicidal activities of compounds 1–7 were evaluated. The bioassay results revealed that compound 1 displays potent fungicidal activities against C. mebaldsii and F. graminearum with the EC50 values of 15.7 and 68.6 mg/L, respectively. According to our knowledge, this is one of few studies on fungicidal agents derived from P. euphratica, providing an innovative structural model for fungicide design.
Supplementary Materials
The following supporting information can be downloaded at https://www.mdpi.com/article/10.3390/ijms26052187/s1: NMR data for 1H and 13C in CDCl3 of 2–4, along with general procedures, detailed isolation procedures, characterization data, and NMR, HRESIMS, UV, and CD spectra for compounds 1–7, as well as X-ray crystallography data for compound 1. ECD calculations for compounds 1–7 can also be found here. Reference [15] are cited in the Supplementary Materials.
Author Contributions
Y.-X.C. was responsible for the conception and design of the experiments and the paper, while Q.J. and D.H. conducted the biological experiments. Y.-Y.L. executed the chemical experiments. D.H. reviewed and revised the paper. All authors have read and agreed to the published version of the manuscript.
Funding
This research received financial support from the Shenzhen Fundamental Research Program (JCYJ20200109114003921).
Institutional Review Board Statement
Not applicable.
Informed Consent Statement
Not applicable.
Data Availability Statement
All the data in this research are presented in manuscript and Supplementary Materials.
Conflicts of Interest
The authors declare no conflicts of interest.
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Figure 1.
The chemical structures of compounds 1–7.
Figure 2.
1H-1H COSY and key HMBC correlations of 1–7.
Figure 3.
Key ROESY correlations of 1–7.
Figure 4.
X-ray structures of 1. Comparison of B3LYP/6-311g(d,p) calculated ECD spectra together with the experimental spectra of 1–7 in MeOH. 1: ☌ = 0.3 eV; shift = 11 nm, scaling factor = 2.5; 2: ☌ = 0.29 eV, shift = 10 nm, scaling factor = 0.9; 3/4: ☌ = 0.29 eV; shift = 25 nm, scaling factor = 1.53; 5: ☌ = 0.29 eV, shift = 10 nm, scaling factor = 1.67; 6: ☌ = 0.35 eV, shift = 23 nm, scaling factor = 4.5; 7: ☌ = 0.27 eV, shift = 0 nm, scaling factor = 26.5.
Figure 4.
X-ray structures of 1. Comparison of B3LYP/6-311g(d,p) calculated ECD spectra together with the experimental spectra of 1–7 in MeOH. 1: ☌ = 0.3 eV; shift = 11 nm, scaling factor = 2.5; 2: ☌ = 0.29 eV, shift = 10 nm, scaling factor = 0.9; 3/4: ☌ = 0.29 eV; shift = 25 nm, scaling factor = 1.53; 5: ☌ = 0.29 eV, shift = 10 nm, scaling factor = 1.67; 6: ☌ = 0.35 eV, shift = 23 nm, scaling factor = 4.5; 7: ☌ = 0.27 eV, shift = 0 nm, scaling factor = 26.5.
Figure 5.
The fungicidal efficacy of compounds 1 and 2.
Table 1.
1H NMR (600 MHz) data for 1–4 (δ in ppm, J in Hz).
| No | 1 a | 2 b | 3 b | 4 b |
|---|---|---|---|---|
| 1 | 2.28, m | 2.27, overlap | 2.26, overlap | 2.26, overlap |
| 2 | Ha: 1.94, m | Ha: 2.27, overlap | Ha: 2.26, overlap | Ha: 2.26, overlap |
| Hb: 1.68, overlap | Hb: 1.68, m | Hb: 1.68, m | Hb: 1.67, overlap | |
| 3 | Ha: 1.84, m | Ha: 2.05, m | Ha: 2.04, m | Ha: 2.05, m |
| Hb: 1.68, overlap | Hb: 1.67, m | Hb: 1.67, m | Hb: 1.67, overlap | |
| 5 | 1.43, t (11.0) | 1.74, t (10.5) | 1.72, t (10.4) | 1.77, t (10.3) |
| 6 | 0.60, t-like (11.0) | 0.64, t-like (10.5) | 0.61, t (10.4) | 0.58, t (10.4) |
| 7 | 0.77, td (11.0, 6.6) | 0.77, td (10.5, 6.1) | 0.79, td (10.4, 6.4) | 0.94, td (10.4, 6.4) |
| 8 | Ha: 2.02, m | Ha: 1.97, m | Ha: 1.93, dt (13.0, 6.4) | Ha: 2.03, m |
| Hb: 0.99, m | Hb: 1.13, m | Hb: 1.08, q-like (13.0) | Hb: 1.15, q-like (12.8) | |
| 9 | Ha: 2.43, dd (13.0, 6.5) | Ha: 2.48, dd (13.2, 5.9) | Ha: 2.48, dd (13.0, 6.4) | Ha: 2.48, dd (12.8, 6.0) |
| Hb: 1.98, m | Hb: 2.14, t (13.2) | Hb: 2.12, t (13.0) | Hb: 2.13, t (12.8) | |
| 11 | 1.24, s | 1.54, s | 1.51, s | 1.54, s |
| 12 | Ha: 4.73, br s | Ha: 4.89, br s | Ha: 4.88, br s | Ha: 4.89, br s |
| Hb: 4.69, br s | Hb: 4.80, br s | Hb: 4.81, br s | Hb: 4.81, br s | |
| 14 | 1.03, s | 1.17, s | 1.21, s | 1.28, s |
| 15 | Ha: 2.83, d (17.9) | Ha: 2.06, m | Ha: 2.02, dd (13.7, 6.6) | Ha: 1.63, dd (14.3, 4.1) |
| Hb: 1.95, d (17.9) | Hb: 2.03, m | Hb: 1.27, dd (13.7, 6.6) | Hb: 1.57, dd (14.3, 8.4) | |
| 16 | 5.77, td (15.7, 7.1) | 4.21, dt (9.4, 6.6) | 4.23, td (8.4, 4.1) | |
| 17 | 6.00, br s | 5.66, d (15.7) | 5.14, d (9.4) | 5.20, br d (8.4) |
| 19 | 1.87, d (0.8) | 1.31, s | 1.75, s | 1.72, br s |
| 20 | 2.14, d (0.8) | 1.31, s | 1.70, s | 1.70, br s |
| 21 | 3.19, s | 3.27, s | 3.28, s | |
| 4-OH | 5.37, s | 5.15, s | 5.29, s |
a NMR spectra data were recorded in CDCl3. b NMR spectra data were recorded in pyridine-d5.
Table 2.
13C NMR (150 MHz) data for 1–7 (δ in ppm).
| No | 1 a | 2 b | 3 b | 4 b | 5 b | 6 a | 7 a |
|---|---|---|---|---|---|---|---|
| 1 | 49.0, CH | 54.3, CH | 53.4, CH | 54.0, CH | 54.0, CH | 49.1, CH | 52.2, CH |
| 2 | 24.2, CH2 | 27.6, CH2 | 27.2, CH2 | 27.5, CH2 | 29.8, CH2 | 24.3, CH2 | 26.8, CH2 |
| 3 | 39.5, CH2 | 43.0, CH2 | 42.5, CH2 | 42.9, CH2 | 35.6, CH2 | 39.5, CH2 | 41.2, CH2 |
| 4 | 79.8, C | 80.3, C | 80.2, C | 80.2, C | 36.2, CH | 80.5, C | 81.2, C |
| 5 | 53.5, CH | 54.3, CH | 54.3, CH | 54.3, CH | 44.1, CH | 53.3, CH | 52.9, CH |
| 6 | 24.7, CH | 29.9, CH | 29.9, CH | 30.0, CH | 28.3, CH | 24.9, CH | 32.4, CH |
| 7 | 26.5, CH | 26.8, CH | 27.3, CH | 27.8, CH | 26.6, CH | 26.9, CH | 31.2, CH |
| 8 | 25.1, CH2 | 25.5, CH2 | 25.6, CH2 | 25.5, CH2 | 25.4, CH2 | 25.2, CH2 | 24.6, CH2 |
| 9 | 39.1, CH2 | 39.6, CH2 | 39.7, CH2 | 39.7, CH2 | 39.6, CH2 | 38.9, CH2 | 38.4, CH2 |
| 10 | 154.3, C | 154.4, C | 154.7, C | 154.6, C | 154.7, C | 154.0, C | 152.3, C |
| 11 | 23.9, CH3 | 27.3, CH3 | 26.6, CH3 | 26.9, CH3 | 18.0, CH3 | 23.9, CH3 | 25.9, CH3 |
| 12 | 106.7, CH2 | 106.7, CH2 | 106.7, CH2 | 106.6, CH2 | 106.4, CH2 | 107.0, CH2 | 107.7, CH2 |
| 13 | 20.5, C | 24.9, C | 22.7, C | 23.2, C | 24.7, C | 21.0, C | 30.3, C |
| 14 | 14.5, CH3 | 14.6, CH3 | 14.9, CH3 | 15.3, CH3 | 14.0, CH3 | 14.3, CH3 | 23.5, CH3 |
| 15 | 56.6, CH2 | 46.4, CH2 | 49.6, CH2 | 49.8, CH2 | 46.3, CH2 | 46.2, CH2 | 177.4, C |
| 16 | 201.0, C | 128.6, CH | 76.6, CH | 76.9, CH | 126.7, CH | 176.6, C | |
| 17 | 124.1, CH | 137.8, CH | 127.9, CH | 128.2, CH | 138.7, CH | ||
| 18 | 155.8, C | 75.2, C | 135.3, C | 134.9, C | 73.6, C | ||
| 19 | 27.9, CH3 | 26.9, CH3 | 26.2, CH3 | 26.2, CH3 | 25.9, CH3 | ||
| 20 | 21.0, CH3 | 26.2, CH3 | 18.6, CH3 | 18.6, CH3 | 71.5, CH3 | ||
| 21 | 50.5, CH3 | 55.6, CH3 | 55.8, CH3 |
a NMR spectra data were recorded in CDCl3. b NMR spectra data were recorded in pyridine-d5.
Table 3.
1H NMR (600 MHz) data of 5–7 (δ in ppm, J in Hz).
| No | 5 b | 6 a | 7 a |
|---|---|---|---|
| 1 | 2.17, m | 2.30, m | 2.18, td (10.7, 6.6) |
| 2 | Ha: 1.66, m | Ha: 1.95, m | Ha: 1.92, m |
| Hb: 1.57, m | Hb: 1.67, m | Hb: 1.67, m | |
| 3 | Ha: 1.79, ddd (12.6, 6.4, 3.2) | Ha: 1.81, m | Ha: 1.86, m |
| Hb: 1.16, m | Hb: 1.68, m | Hb: 1.57, ddd (12.7, 10.4, 6.5) | |
| 4 | 2.03, m | ||
| 5 | 1.39, q (10.4) | 1.41, t (10.8), | 1.95, t (10.7) |
| 6 | 0.65, t (10.4) | 0.73, t (10.8) | 0.98, t-like (10.7) |
| 7 | 0.74, td (10.4, 6.6) | 0.88, td (10.8, 6.8) | 1.20, td (10.7, 6.1) |
| 8 | Ha: 1.90, dt (12.5, 6.1) | Ha: 2.05, dt (14.6, 6.8) | Ha: 2.03, m |
| Hb: 1.04, m | Hb: 0.98, m | Hb: 1.45, q-like (12.3) | |
| 9 | Ha: 2.42, dd (13.1, 6.1) | Ha: 2.43, dd (13.2, 6.8) | Ha: 2.44, dd (13.6, 6.4) |
| Hb: 2.05, m | Hb: 1.99, m | Hb: 2.01, m | |
| 11 | 1.01, d (8.6) | 1.29, s | 1.35, s |
| 12 | 4.76, s | Ha: 4.74, br s | Ha: 4.72, br s |
| Hb: 4.71, br s | Hb: 4.69, br s | ||
| 14 | 1.00, s | 1.08, s | 1.35, s |
| 15 | 2.06, m | Ha: 2.68, d (16.8) | |
| Hb: 1.87, d (16.8) | |||
| 16 | 6.18, dt (15.0, 7.1) | ||
| 17 | 6.03, d (15.0) | ||
| 19 | 1.67, (s) | ||
| 20 | 3.98, d (10.4) | ||
| 3.93, d (10.4) |
a NMR spectra data were recorded in CDCl3. b NMR spectra data were recorded in pyridine-d5.
Table 4.
Fungicidal activities of compounds 1–7 at 80 mg/L.
| Cpd. | FG * | CM | CL | BC | AA | SS | RS |
|---|---|---|---|---|---|---|---|
| 1 | 61.4 ± 4.3 | 80.0 ± 5.3 | 54.5 ± 0.0 | 36.2 ± 7.9 | 53.3 ± 2.9 | 61.4 ± 6.1 | 56.0 ± 9.2 |
| 2 | 55.7 ± 6.5 | 60.0 ± 2.7 | 51.5 ± 2.6 | 55.2 ± 6.0 | 53.3 ± 2.9 | 36.8 ± 13.9 | 52.0 ± 0.0 |
| 3 | 65.7 ± 0.0 | NT ** | 47.0 ± 2.6 | 56.9 ± 6.0 | 51.7 ± 2.9 | 66.7 ± 8.0 | 38.0 ± 3.5 |
| 4 | 58.6 ± 2.5 | NT | NT | 34.5 ± 7.9 | 51.7 ± 5.8 | 49.1 ± 13.2 | 40.0 ± 0.0 |
| 5 | 54.3 ± 6.5 | 72.3 ± 0.0 | NT | 56.9 ± 3.0 | 63.3 ± 2.9 | 40.4 ± 8.0 | 40.0 ± 6.0 |
| 6 | 37.1 ± 4.9 | NT | NT | 5.2 ± 3.0 | 13.3 ± 2.9 | 36.8 ± 0.0 | 20.0 ± 3.5 |
| 7 | NT | NT | NT | 34.5 ± 6.0 | NT | 33.3 ± 3.0 | NT |
| hymexazol | 61.4 ± 0.0 | 50.8 ± 2.7 | 83.3 ± 2.6 | 70.7 ± 3.0 | 66.7 ± 2.9 | 61.4 ± 3.0 | 62.0 ± 3.5 |
* FG: Fusarium graminearum; CM: Curvularia mebaldsii; CL: Curvularia lunata; BC: Botrytis cinerea; AA: Alternaria altanata; SS: Sclerotinia sclerotiorum; RS: Rhizoctonia solani. ** NT means no test.
Table 5.
The EC50 values of compounds 1 and 2.
| Compound | R2 | Regression Equation (y = ax + b) | EC50 (mg/L) | |
|---|---|---|---|---|
| C. mebaldsii | 1 | 0.943 | y = 1.171x + 3.601 | 15.7 |
| 2 | 0.950 | y = 0.712x + 3.844 | 42.1 | |
| hymexazol | 0.953 | y = 2.314x + 0.537 | 84.8 | |
| F. graminearum | 1 | 0.961 | y = 1.426x + 2.381 | 68.6 |
| 2 | 0.983 | y = 1.369x + 2.410 | 78.0 | |
| hymexazol | 0.961 | y = 1.561x + 2.157 | 66.3 |
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Jiang, Q.; Liu, Y.-Y.; Huang, D.; Cheng, Y.-X. Euphraticanoids N–T: Aromadendrane-Type Diterpenes and Sesquiterpenes with Fungicidal Activities from Populus euphratica Resins. Int. J. Mol. Sci. 2025, 26, 2187. https://doi.org/10.3390/ijms26052187
AMA Style
Jiang Q, Liu Y-Y, Huang D, Cheng Y-X. Euphraticanoids N–T: Aromadendrane-Type Diterpenes and Sesquiterpenes with Fungicidal Activities from Populus euphratica Resins. International Journal of Molecular Sciences. 2025; 26(5):2187. https://doi.org/10.3390/ijms26052187
Chicago/Turabian StyleJiang, Qinbin, Yun-Yun Liu, Danling Huang, and Yong-Xian Cheng. 2025. "Euphraticanoids N–T: Aromadendrane-Type Diterpenes and Sesquiterpenes with Fungicidal Activities from Populus euphratica Resins" International Journal of Molecular Sciences 26, no. 5: 2187. https://doi.org/10.3390/ijms26052187
APA StyleJiang, Q., Liu, Y.-Y., Huang, D., & Cheng, Y.-X. (2025). Euphraticanoids N–T: Aromadendrane-Type Diterpenes and Sesquiterpenes with Fungicidal Activities from Populus euphratica Resins. International Journal of Molecular Sciences, 26(5), 2187. https://doi.org/10.3390/ijms26052187
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