Chemical and Pharmaceutical Bulletin
Online ISSN : 1347-5223
Print ISSN : 0009-2363
ISSN-L : 0009-2363
Notes
Tetracyclic Triterpenoids, Steroids and Lignanes from the Aerial Parts of Oxypetalum caeruleum
Tsutomu WarashinaOsamu Shirota
Author information
JOURNALS FREE ACCESS FULL-TEXT HTML
Supplementary material

2021 Volume 69 Issue 2 Pages 226-231

Details
Abstract

The MeOH extract from dried aerial parts of Oxypetalum caeruleum (Apocynaceae) plants yielded seventeen compounds, including four new tetracyclic triterpenoids, one pregnane glycoside, two lignane glycosides, and ten known compounds. The structures of the new compounds were established using NMR, MS spectroscopic analysis and chemical evidence.

Introduction

The genus Oxypetalum was classified to the Asclepiadaceaus family, and this family was recently included in Apocynaceae. O. caeruleum (Apocynaceae) is indigenous to South America and is distributed as a garden plant in Japan, but the composition of this plant has not yet been investigated in detail. The presence of cardenolides and/or steroidal glycosides was revealed in the previous studies on phytochemicals in Apocynaceaus (Asclepiadaceaus) plants.17) Since these compounds are characteristic of the Apocynaceaus (including Asclepiadaceaus) and Scrophoulariaceaus families, we investigated the constituents of this plant.

Results and Discussion

A MeOH extract from the dried aerial parts of O. caeruleum plants was suspended in 90% MeOH in water. The solution was extracted with n-hexane and partitioned into a n-hexane-soluble fraction and a 90% MeOH in water-soluble fraction. The 90% MeOH in water-soluble fraction was dried in vacuo, and the residue was suspended in water. The suspension was extracted with diethylether and partitioned into an ether-soluble fraction and a water-soluble fraction. The residues of the ether-soluble fraction and the water-soluble fraction were subjected to silica gel column chromatography and semi-preparative HPLC to give nine tetracyclic triterpenoids, two pregnanes, one pregnane glycoside, three lignanes and two lignane glycosides. Compounds 3S,24S,25-trihydroxy-tirucall-7-ene (6),8,9) (3β,24S)-euph-7,25-diene-3,24-diol (7),10) (3β,24R)-euph-7,25-diene-3,24-diol (8),10) 3β-hydroxy-cycloart-23-ene-25-methylester (9),11,12) cortexone (10),13) 6,7-didehydrocortexone (11),14) (+)-pinoresinol (13),15,16) (+)-medioresinol (14),16) and (−)-syringaresinol (15)16,17) were identified as shown in Chart 1 based on the 1H- and 13C-NMR spectroscopic data. This paper described the structural elucidation of new compounds from this plant.

Chart 1. Structures of Compounds 1–17

The molecular formula of compound 1, C30H50O2, was established based on high resolution (HR)-electrospray ionization (ESI)-MS molecular ion at 465.3713 ([M + Na]+). The molecular formula indicated the presence of six units of unsaturation. The 1H-NMR spectrum of 1 displayed signals for seven tertiary methyl groups [δH 1.31 (6H, s), 0.98 (3H, s), 0.97 (3H, s), 0.86 (3H, s), 0.83 (3H, s), 0.75 (3H, s)], one secondary methyl group [δH 0.82 (3H, d, J = 6.0 Hz)], three olefinic protons [δH 5.58 (2H, overlapping), 5.24 (1H, dd, J = 6.5, 3.5 Hz)], and one oxygenated methine proton [δH 3.24 (1H, dd, J = 11.5, 4.0 Hz)]. The 13C-NMR spectrum of 1 showed thirty carbon signals, which were classified by the distorsionless enhancement by polarization transfer (DEPT) experiment as eight sp3 methyls, eight sp3 methylenes, five sp3 methines (one oxygenated at δC 79.2), five sp3 quartenary carbons (one oxygenated at δC 70.7), and four olefinic carbons [δC 145.7 (C), 139.1 (CH), 126.1 (CH), 117.9 (CH)]. Compound 1 must have a tetracyclic system since there are two olefinic groups in its structure. Based on the 1JC–H correlations in a 1H-detected heteronuclear single-quantum correlation spectroscopy (HSQC) measurement, the carbon and proton signals were assigned as in Table 1 and the experimental section. These data were in good agreement with those of (23E)-3β-acetoxyeuph-7,23-dien-25-ol18,19) except for the signal around the C-3 position. In the NMR spectroscopic data of 1, the acetyl group signals disappeared, and the carbinol proton and carbon signals at δH 3.24 and δC 79.2 were assigned at the H-3 and C-3 positions, respectively. Moreover, the large coupling constant (J = 11.5 Hz) suggested that this hydroxy group retained β-orientation. The results of the 1H–1H shift correlation spectroscopy (COSY), 1H-detected heteronuclear multiple-bond connectivity (HMBC), and rotating frame nuclear Overhauser effect correlation spectroscopy (ROESY) experiments showed in Chart 2. Based on the above evidence, compound 1 was determined to be (23E)-3β,25-dihydroxyeuph-7,23-diene.

Table 1. 13C-NMR Spectroscopic Data of Compounds 15
Carbon No.12345
137.237.237.237.037.0
227.7a)27.7a)27.7a)26.626.6
379.279.279.379.179.1
439.039.039.038.038.0
550.650.650.665.265.2
624.024.023.9200.0199.9
7117.9117.9117.9125.0125.0
8145.7145.7145.8170.5170.4
948.948.948.950.450.3
1034.934.934.943.843.8
1118.118.118.117.517.6
1233.8b)33.833.732.732.8
1343.643.643.543.043.1
1451.351.351.152.352.4a)
1533.9b)33.934.033.032.8
1628.328.328.127.627.7
1753.153.152.652.152.5a)
1822.222.222.021.922.1
1913.113.113.114.314.3
2036.236.236.436.235.9
2118.818.918.518.418.7
2238.038.339.138.738.0
23126.1129.3128.7125.1125.6
24139.1136.3136.6139.7139.4
2570.774.974.970.770.7
2629.925.8b)25.8b)29.9a)29.9b)
2729.926.1b)26.2b)30.0a)30.0b)
2827.6a)27.6a)27.6a)28.328.3
2914.714.714.714.814.8
3027.327.327.224.924.9
–OMe50.350.3

Measured in CDCl3. a, b) Interchangeable in each column.

Chart 2. Observed Key 1H–1H COSY, HMBC and ROE Correlations for Compound 1

The molecular formulae of compounds 2 and 3 were proposed to be C31H52O2, one CH2 mass unit larger than 1, based on HR-ESI-MS. The NMR spectra of the tetracyclic systems in 2 and 3 closely resembled those of 1, and one methoxy proton and one carbon signal were observed at δH 3.15 (3H, s) and δC 50.3, respectively. Because this methoxy proton signal showed long-range correlation to C-25 (δC 74.9) in the HMBC experiment, both compounds had a methoxy group at the C-25 position. In a comparison of the 13C-NMR spectroscopic data of 2 with those of 3, slight differences were seen in the signals of C-17, C-20, C-21, and C-22. In the ROESY experiments for 2 and 3, the ROE correlations of each tetracyclic system were consistent with those of 1. Thus, either 2 or 3 was the euphane-type triterpenoid, and the other was the tirucallane-type triterpenoid. In the side chain of 2, ROEs were observed between H-18 (δH 0.84) and H-20 (δH 1.49)/H-22 (δH 2.38); H-12 (δH 1.82) and H-22 (δH 2.38); and H-21 (δH 0.83) and H-16 (δH 1.94, 1.30).10,20,21) Since these ROE correlations were observed in 1, 2 was considered to be the euphane-type triterpenoid. In the side chain of 3, ROEs were observed between H-18 (δH 0.82) and H-20 (δH 1.47); H-16 (δH 1.96) and H-22 (δH 2.20); and H-21 (δH 0.87) and H-12 (δH 1.76, 1.61).2023)As the 13C-NMR spectroscopic data of the side chain in 3 were consistent with those of (−)-leucophyllone,24) 3 was considered to be the tirucallane-type triterpenoid. On the basis of the above evidence, 2 and 3 were identified as (23E)-3β-hydroxy-25-methoxyeuph-7,23-diene and (23E)-3β-hydroxy-25-methoxytirucall-7,23-diene. Compound 2 was previously reported to be a tirucallane-type triterpenoid,25) but the results of the ROESY experiment in 2 and inconsistency of the 13C-NMR spectroscopic data of the side chain in 2 with those of (−)-leucophyllone supported compound 2 being the euphane-type triterpenoid.

The molecular formulae of compounds 4 and 5 were established to be C30H48O3, based on HR-ESI-MS. The 13C-NMR spectroscopic data of 4 and 5 resembled those of 2 and 3, but instead of the one sp3 methylene carbon signal, carbonyl carbon signals were observed at δC 200.0 in 4 and at δC 199.9 in 5. The chemical shifts of these carbonyl signals suggested the presence of α,β-unsaturated carbonyl groups. In the HMBC experiments for 4 and 5, long-range correlations were observed between the carbonyl signals to H-5 (δH 2.12 in 4, δH 2.13 in 5) and H-7 (δH 5.70 in 4, δH 5.70 in 5). Thus, the carbonyl signal was assigned at the C-6 position. In the ROESY experiments for 4 and 5, important ROE correlations were observed between H-3 and H-5/H-28; H-5 and H-9/H-28; H-9 and H-18; H-19 and H-29/H-30; and H-30 and H-17. Thus, either 4 or 5 was also the euphane-type triterpenoid, and the other was the tirucallane-type triterpenoid. Additionally, in 4, ROEs were revealed between H-18 (δH 0.84) and H-20 (δH 1.47); H-21 (δH 0.88) and H-12 (δH 1.85, 1.73); and H-22 (δH 2.18) and H-16 (δH 2.02, 1.36), as was the case for 3. In contrast, in 5, ROEs were revealed between H-18 (δH 0.85) and H-20 (δH 1.48); H-21 (δH 0.84) and H-16 (δH 1.99, 1.35); and H-22 (δH 2.33) and H-12 (δH 1.89), as was the case for 2. Thus, compounds 4 and 5 were determined to be (23E)-3β,25-dihydroxytirucall-7,23-dien-6-one and (23E)-3β,25-dihydroxyeuph-7,23-dien-6-one, respectively. Consistency of the 1H- and 13C-NMR spectroscopic data of the side chain in 4 with those of (23E)-25-hydroxytirucall-7,23-diene-3,6-dione (aphanamgrandin K)26) supported this structure.

The molecular formula of 12 was identified as C44H58O17 by HR-ESI-MS. Alkaline hydrolysis of 12 afforded (trans)-sinapinic acid, and subsequent enzymatic and acid hydrolysis gave 6,7-didehydrocortexone (11) and D-glucose. Thus, 12 was considered to be 6,7-didehydrocortexone glycoside, which consisted of D-glucose and (trans)-sinapinic acid. The 1H- and 13C-NMR spectroscopic data of 12 showed two sets of anomeric proton and carbon signals at δH 4.38 (2H, d, J = 8.0 Hz) and δC 104.8, 103.5. In addition, six aromatic carbons (δC 149.6 × 2, 140.0, 126.4, 107.0 × 2), two olefinic carbons (δC 147.4, 115.7), one carboxylic carbon (δC 168.7), two aromatic methoxy carbon signals (δC 56.9 × 2) and AA′-type aromatic protons [δH 6.93 (2H, s)], two olefinic protons [δH 7.63 (1H, d, J = 16.0 Hz), 6.46 (1H, d, J = 16.0 Hz)] and two aromatic methoxy proton signals [δH 3.86 (6H, s)], were seen, derived from the (trans)-sinapinoyl group. On the basis of the two-dimensional (2D)-NMR (HSQC, HMBC and 1H–1H COSY) experiments, the signal assignments of sugar and ester moieties were carried out as described in Experimental. The remaining twenty-one carbon signals were assigned to the aglycone moiety by comparison with those of 6,7-didehydrocortexone, and confirmed by 2D-NMR (HSQC, HMBC, 1H–1H COSY and ROESY) experiments (Chart 3). The sugar and ester linkages were determined by the HMBC and/or ROESY experiments. Long-range correlations were observed between H-1′ of β-D-glucopyranose (δH 4.38) and C-21 (δC 75.1); H-21 (δH 4.32, 4.20) and C-1′ of β-D-glucopyranose (δC 103.5); H-4′ of β-D-glucopyranose (δH 3.63) and C-1″ of β-D-glucopyranose (δC 104.8); H-1″of β-D-glucopyranose (δH 4.38) and C-4′ of β-D-glucopyranose (δC 81.0); and H-6′ of β-D-glucopyranose (δH 4.64, 4.49) and C-α (δC 168.7). The ROE correlations between H-1′ of β-D-glucopyranose (δH 4.38) and H-21 (δH 4.32, 4.20); and H-1″ of β-D-glucopyranose (δH 4.38) and H-4′ of β-D-glucopyranose (δH 3.63) supported this sugar linkage. Hence, the structure of 12 was identified as 6,7-didehydrocortexone 21-O-β-D-glucopyranosyl-(1→4)-β-D-[6-O-4-hydroxy-3,5-dimethoxy-(E)-cinnamoyl]-glucopyranoside, and was named oxypetalumoside I.

Chart 3. Observed Key 1H–1H COSY, HMBC and ROE Correlations for Compound 12

The molecular formulae of compounds 16 and 17 were determined to be C45H56O22 and C44H54O21, respectively, on the basis of HR-ESI-MS spectra. The NMR spectroscopic data of 16 showed two anomeric proton and carbon signals [δH 4.85 (overlapping), 4.37 (1H, J = 8.0 Hz) and δC 104.6, 104.9] and signals derived from the (trans)-sinapinoyl group [δH 7.52 (1H, J = 16.0 Hz), 6.90 (2H, s), 6.31 (1H, J = 16.0 Hz), 3.88 (6H, s) and δC 168.6, 149.6 × 2, 147.0, 139.7, 126.6, 115.8, 106.9 × 2, 56.8 × 2]. Since these signals were almost consistent with those of 12, 16 also possessed the β-D-glucopyranosyl-(1→4)-β-D-[6-O-4-hydroxy-3,5-dimethoxy-(E)-cinnamoyl]-glucopyranosyl unit in its structure. In regard to the NMR spectroscopic data of the aglycone moiety in 16, the signals [δH 6.58 (2H, s), δC 154.7 × 2. 139.7, 134.8, 104.2 × 2 and δH 6.64 (2H, s), δC 149.3 × 2, 136.2, 133.0, 104.6 × 2] suggested the presence of two 1,3,4,5-tetrasubstituted aromatic rings. In the 13C-NMR spectroscopic data, the characteristic signals (δC 87.7, 86.8, 72.6, 72.5, 55.8, 55.6) revealed the existence of a 2,6-diaryltetrahydrofuran ring system.16) In consideration of the observation of four aromatic methoxy signals [δH 3.85 (6H, s), 3.81 (6H, s)] and the consequence of enzymatic hydrolysis, the aglycone moiety of 16 was determined to be syringaresinol. The sugar and ester linkages were confirmed by HMBC and ROESY experiments. Long-range correlations were observed between H-1′ of β-D-glucopyranose (δH 4.85) and C-4 (δC 134.8); H-1″ of β-D-glucopyranose (δH 4.37) and C-4′ of β-D-glucopyranose (δC 81.4); H-4′ of β-D-glucopyranose (δH 3.65) and C-1″ of β-D-glucopyranose (δC 104.9); and H-6′ of β-D-glucopyranose (δH 4.53, 4.48) and C-α (δC 168.6). A ROE correlation was also detected between H-1″ of β-D-glucopyranose (δH 4.37) and H-4′ of β-D-glucopyranose (δH 3.65). Thus, the structure of 16 was established as syringaresinol 4-O-β-D-glucopyranosyl-(1→4)-β-D-[6-O-4-hydroxy-3,5-dimethoxy-(E)-cinnamoyl]-glucopyranoside.

The NMR spectroscopic data of 17 were almost consistent with those of 16, except for those of the ester moiety. The 1H-NMR spectroscopic data of the ester moiety showed AMX-type aromatic proton signals [δH 7.17 (1H, d, J = 2.0 Hz), 7.05 (1H, dd, J = 8.0, 2.0 Hz), 6.83 (1H, d, J = 8.0 Hz)], two olefinic proton signals [δH 7.52 (1H, d, J = 16.0 Hz), 6.27 (1H, d, J = 16.0 Hz)] and one aromatic methoxy proton signal [δH 3.89 (3H, s)]. The ester moiety of 17 was thereby determined to be a (trans)-feruloyl group, which was confirmed by alkaline hydrolysis. Thus, 17 was determined to be syringaresinol 4-O-β-D-glucopyranosyl-(1→4)-β-D-[6-O-4-hydroxy-3-methoxy-(E)-cinnamoyl]-glucopyranoside. The absolute configurations of the aglycone moieties of 16 and 17, syringaresinol, remain ambiguous because of the difficulty of obtaining aglycones through hydrolysis due to the low yield of each compound. Compounds 16 and 17 were named oxypetalumosides II and III, respectively.

In this phytochemical investigation of O. caeruleum, nine tetracyclic triterpenoids, two pregnanes, one pregnane glycoside, three lignanes and two lignane glycosides were afforded along with some flavonoid glycosides. Triterpenoids of euphane- and tirucallane-type are found in many families, mainly Maliaceae and Euphorbiaceae. To the best of our knowledge, this is the first time they have been obtained from Apocynaceae (Asclepiadaceae). They are widely distributed in many plants, as are flavonoids and lignanes, and therefore are not considered to be chemotaxonomic compounds in the Apocynaceaus (Asclepiadaceaus) family. Many kinds of pregnanes and their glycosides are detected in the Apocynaceaus (including Asclepiadaceaus) and Scrophoulariaceaus plants. The fact that O. caeruleum only yielded pregnanes and their glycosides, albeit in small quantities, still indicates that these compounds are characteristic of this family. The general pregnane glucosides in Apocynaceaus (Asclepiadaceaus) plants possess deoxysugars in their sugar sequence.2,3,57) However, it is unusual for the sugar sequence of oxypetalumoside I to be composed of two D-glucoses.

In addition to cytotoxic activities against tumor cell lines and antimicrobial activities in vitro, some euphane- and tirucallane-type triterpenoids show inhibitory effects on 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced inflammation in mice.27) Since TPA is a powerful carcinogenic promoter,28) and inhibition of TPA-induced inflammation has been demonstrated to have an almost parallel inhibitory effect against tumor promotion, plants that include these compounds are expected to inhibit carcinogenic effects. Extracts of the Apocynaceaus (Asclepiadaceaus) plants have been shown to have proliferative effects on human skin fibroblasts in the studies from the cosmetics field,29,30) and pregnane glycosides were found to be among the effective compounds.31) Previous studies have shown that the roots of the Apocynaceaus (Asclepiadaceaus) plants contain many pregnane glycosides.2,3,57) We are interested in the constituents of O. caeruleum with respect to its usefulness outside of plant appreciation.

Experimental

A part of this section (general procedures, plant materials, extraction and isolation, and alkaline hydrolysis) was described as supplementary materials.

(23E)-3β,25-Dihydroxyeuph-7.23-diene (1)

Amorphous powder. [α]D20 −14 (c = 0.75, CHCl3). HR-ESI-MS: m/z 465.3713 [M + Na]+ (Calcd for C30H50O2Na: 465.3709). 1H-NMR data (measured in CDCl3) δ: 5.58 (2H, overlapping, H-23, H-24), 5.24 (1H, dd, J = 6.5, 3.5 Hz, H-7), 3.24 (1H, dd, J = 11.5, 4.0 Hz, H-3), 2.34 (1H, dt, J = 14.0, 3.5 Hz, H-22), 2.20 (1H, m, H-9), 2.14 (1H, br d, J = 18.0 Hz, H-6), 1.96 (1H, m, H-6), 1.93 (1H, m, H-16), 1.81 (1H, br dd, J = 13.5, 10.0 Hz, H-12), 1.68 (overlapping, H-1), 1.67 (overlapping, H-22), 1.64 (overlapping, H-2, H-12), 1.62 (overlapping, H-2), 1.52 (overlapping, H-11), 1.50 (overlapping, H-17), 1.47 (overlapping, H-20), 1.45 (overlapping, H-15), 1.31 (6H, s, H-26, H-27), 1.31 (overlapping, H-5), 1.28 (1H, m, H-16), 1.14 (1H, td, J = 14.5, 4.0 Hz, H-1), 0.98 (3H, s, H-30), 0.97 (3H, s, H-28), 0.86 (3H, s, H-29), 0.83 (3H, s, H-18), 0.82 (3H, d, J = 6.0 Hz, H-21), 0.75 (3H, s, H-19).

(23E)-3β-Hydroxy-25-methoxyeuph-7,23-diene (2)

Amorphous powder. [α]D18 −10 (c = 0.41, CHCl3). HR-ESI-MS: m/z 479.3875 [M + Na]+ (Calcd for C31H52O2Na: 479.3865). 1H-NMR data (measured in CDCl3) δ: 5.51 (1H, dt, J = 15.5, 7.0 Hz, H-23), 5.38 (1H, br d, J = 15.5 Hz, H-24), 5.27 (1H, q, J = 3.5 Hz, H-7), 3.25 (1H, dd, J = 11.5, 4.0 Hz, H-3), 3.15 (3H, s, –OMe), 2.38 (1H, br d, J = 16.0 Hz, H-22), 2.21 (1H, m, H-9), 2.15 (1H, br d, J = 18.0 Hz, H-6), 1.97 (overlapping, H-6), 1.94 (overlapping, H-16), 1.82 (1H, br dd, J = 14.5, 9.5 Hz, H-12), 1.70 (overlapping, H-22), 1.69 (overlapping, H-1), 1.64 (overlapping, H-12), 1.51 (overlapping, H-17), 1.49 (overlapping, H-20), 1.32 (1H, dd, J = 12.0, 5.5 Hz, H-5), 1.30 (overlapping, H-16), 1.25 (6H, s, H-26, H-27), 1.14 (1H, td, J = 13.5, 3.5, H-1), 0.98 (3H, s, H-30), 0.97 (3H, s, H-28), 0.86 (3H, s, H-29), 0.84 (3H, s, H-18), 0.83 (3H, d, J = 6.0 Hz, H-21), 0.75 (3H, s, H-19).

(23E)-3β-Hydroxy-25-methoxytirucall-7,23-diene (3)

Amorphous powder. [α]D20 −43 (c = 0.15, CHCl3). HR-ESI-MS: m/z 479.3871 [M + Na]+ (Calcd for C31H52O2Na: 479.3865). 1H-NMR data (measured in CDCl3) δ: 5.52 (1H, dt, J = 15.5, 6.5 Hz, H-23), 5.40 (1H, br d, J = 15.5 Hz, H-24), 5.26 (1H, q, J = 3.5 Hz, H-7), 3.24 (1H, dd, J = 11.5, 4.0 Hz, H-3), 3.15 (3H, s, –OMe), 2.20 (overlapping, H-9, H-22), 2.14 (1H, br d, J = 18.0 Hz, H-6), 1.96 (overlapping, H-6, H-16), 1.78 (overlapping, H-22), 1.76 (overlapping, H-12), 1.68 (overlapping, H-1), 1.61 (overlapping, H-12), 1.47 (overlapping, H-17, H-20), 1.31 (1H, dd, J = 12.0, 5.5 Hz, H-5), 1.30 (overlapping, H-16), 1.25 (6H, s, H-26, H-27), 1.14 (1H, td, J = 13.0, 4.0 Hz, H-1), 0.97 (3H, s, H-30), 0.96 (3H, s, H-28), 0.87 (3H, d, J = 6.0 Hz, H-21), 0.86 (3H, s, H-29), 0.82 (3H, s, H-18), 0.75 (3H, s, H-19).

(23E)-3β,25-Dihydroxytirucall-7,23-dien-6-one (4)

Amorphous powder. [α]D22 −15 (c = 0.37, MeOH). HR-ESI-MS: m/z 457.3672 [M + H]+ (Calcd for C30H49O3: 457.3682). 1H-NMR data (measured in CDCl3) δ: 5.70 (1H, d, J = 3.0 Hz, H-7), 5.61 (1H, ddd, J = 15.5, 7.0, 5.0 Hz, H-23), 5.61 (1H, br d, J = 15.5 Hz, H-24), 3.22 (1H, dd, J = 12.0, 4.0 Hz, H-3), 2.72 (1H, ddd, J = 13.5, 6.0, 3.0 Hz, H-9), 2.18 (1H, dt, J = 14.5, 3.5 Hz, H-22), 2.12 (1H, s, H-5), 2.02 (1H, m, H-16), 1.85 (1H, m, H-12), 1.76 (overlapping, H-22), 1.73 (overlapping, H-11, H-12), 1.68 (overlapping, H-1), 1.67 (overlapping, H-2), 1.59 (overlapping, H-2), 1.56 (overlapping, H-11, H-15), 1.54 (overlapping, H-17), 1.47 (overlapping, H-20), 1.41 (1H, td, J = 13.0, 4.0 Hz, H-1), 1.36 (1H, m, H-16), 1.32 (6H, s, H-26, H-27), 1.32 (3H, s, H-28), 1.13 (3H, s, H-29), 1.04 (3H, s, H-30), 0.88 (3H, d, J = 6.5 Hz, H-21), 0.86 (3H, s, H-19), 0.84 (3H, s, H-18).

(23E)-3β,25-Dihydroxyeuph-7,23-dien-6-one (5)

Amorphous powder. [α]D18 +15 (c = 0.61, CHCl3). HR-ESI-MS: m/z 479.3505 [M + Na]+ (Calcd for C30H48O3Na: 479.3501). 1H-NMR data (measured in CDCl3) δ: 5.70 (1H, d, J = 3.0 Hz, H-7), 5.59 (1H, br d, J = 15.0 Hz, H-24), 5.58 (overlapping, H-23), 3.22 (1H, dd, J = 12.0, 4.0 Hz, H-3), 2.72 (1H, ddd, J = 13.5, 6.5, 3.0 Hz, H-9), 2.33 (1H, dt, J = 14.5, 3.5 Hz, H-22), 2.13 (1H, s, H-5), 1.99 (1H, m, H-16), 1.89 (1H, t, J = 12.5 Hz, H-12), 1.76 (overlapping, H-12), 1.73 (overlapping, H-11), 1.70 (overlapping, H-1, H-22), 1.67 (overlapping, H-2), 1.60 (overlapping, H-2), 1.58 (overlapping, H-11), 1.57 (overlapping, H-17), 1.48 (overlapping, H-20), 1.41 (overlapping, H-1), 1.35 (overlapping, H-16), 1.32 (6H, s, H-26, H-27), 1.32 (3H, s, H-28), 1.13 (3H, s, H-29), 1.06 (3H, s, H-30), 0.86 (3H, s, H-19), 0.85 (3H, s, H-18), 0.84 (3H, d, J = 6.5 Hz, H-21).

Oxypetalumoside I (12)

Amorphous powder. [α]D19 +29 (c = 0.68, MeOH). HR-ESI-MS: m/z 881.3596 [M + Na]+ (Calcd for C44H58O17Na: 881.3572), 857.3580 [M−H] (Calcd for C44H57O17: 857.3596). UV λmax(MeOH) nm (log ε): 229 (sh), 244 (4.27), 289 (4.45), 332 (4.25). 13C-NMR data (measured in MeOH-d4): aglycone moiety δ: 210.3 (C-20), 202.4 (C-3), 166.9 (C-5), 142.5 (C-7), 128.9 (C-6), 124.0 (C-4), 75.1 (C-21), 59.9 (C-17), 54.7 (C-14), 51.6 (C-9), 46.1 (C-13), 39.2 (C-12), 38.8 (C-8), 37.2 (C-10), 34.6 × 2 (C-1, C-2), 24.8 (C-15), 23.7 (C-16), 21.7 (C-11), 16.4 (C-19), 13.6 (C-18). Sugar moiety δ: 104.8 (Glc-1″), 103.5 (Glc-1′), 81.0 (Glc-4′), 78.3 (Glc-5″), 77.9 (Glc -3″), 76.1 (Glc-3′), 74.9, 74.7 (Glc-2′, Glc-2″), 74.3 (Glc-5′), 71.4 (Glc-4″), 63.9 (Glc-6′), 62.6 (Glc-6″). Ester moiety δ: 168.7 (C-α), 149.6 × 2 (C-3‴, C-5‴), 147.4 (C-γ), 140.0 (C-4‴), 126.4 (C-1‴), 115.7 (C-β), 107.0 × 2 (C-2‴, C-6‴), 56.9 × 2 (–OMe ×2). 1H-NMR data (measured in MeOH-d4): aglycone moiety δ: 6.07 (2H, s, H-6, H-7), 5.59 (1H, s, H-4), 4.32 (1H, d, J = 16.5 Hz, H-21), 4.20 (1H, d, J = 16.5 Hz, H-21), 2.73 (1H, t, J = 9.5 Hz, H-17), 2.49 (1H, ddd, J = 18.0, 14.0, 5.0 Hz, H-2), 2.29 (1H, dd, J = 18.0, 5.0 Hz, H-2), 2.16 (1H, br q, J = 11.0 Hz, H-16), 2.12 (1H, t, J = 11.0 Hz, H-8), 1.89 (overlapping, H-12), 1.73 (overlapping, H-1, H-16), 1.49 (1H, td, J = 14.0, 5.0 Hz, H-1), 1.39 (overlapping, H-11), 1.35 (1H, m, H-15), 1.28 (overlapping, H-11, H-12), 1.15 (1H, td, J = 11.0, 7.0 Hz, H-14), 0.95 (1H, td, J = 11.0, 4.0 Hz, H-9), 0.98 (3H, s, H-19), 0.65 (3H, s, H-18). Sugar moiety δ: 4.64 (1H, dd, J = 12.0, 2.0 Hz, Glc-6′), 4.49 (1H, dd, J = 12.0, 6.0 Hz, Glc-6′), 4.38 (2H, J = 8.0 Hz, Glc-1′, Glc-1″), 3.89 (1H, dd, J = 12.0, 2.5 Hz, Glc-6″), 3.71 (1H, m, Glc-5′), 3.66 (1H, dd, J = 12.0, 6.0 Hz, Glc-6″), 3.63 (1H, t, J = 9.0 Hz, Glc-4′), 3.57 (1H, t, J = 9.0 Hz, Glc-3′), 3.38 (1H, dd, J = 9.0, 8.0 Hz, Glc-2′), 3.36 (overlapping, Glc-5″), 3.36 (1H, t, J = 9.0 Hz, Glc-3″), 3.29 (1H, t, J = 9.0 Hz, Glc-4″), 3.24 (1H, dd, J = 9.0, 8.0 Hz, Glc-2″). Ester moiety δ: 7.63 (1H, d, J = 16.0 Hz, H-γ), 6.93 (2H, s, H-2‴, H-6‴), 6.46 (1H, d, J = 16.0 Hz, H-β), 3.86 (6H, s, –OMe ×2).

Oxypetalumoside II (16)

Amorphous powder. [α]D19 −101 (c = 0.78, MeOH). HR-ESI-MS: m/z 971.3170 [M + Na]+ (Calcd for C45H56O22Na: 971.3161), 947.3158 [M-H]- (Calcd for C45H55O22: 947.3185). UV λmax(MeOH) nm (log ε): 238 (sh), 329 (4.28). 13C-NMR spectroscopic data (measured in MeOH-d4): aglycone moiety δ: 154.7 × 2 (C-3, C-5), 149.3 × 2 (C-3a, C-5a), 139.7 (C-1), 136.2 (C-4a), 134.8 (C-4), 133.0 (C-1a), 104.6 × 2 (C-2a, C-6a), 104.2 × 2 (C-2, C-6), 87.7 (C-7a), 86.8 (C-7), 72.6, 72.5 (C-9, C-9a), 56.9 × 4 (–OMe ×2, –OMea ×2), 55.8 (C-8), 55.6 (C-8a). Sugar moiety δ: 104.9 (Glc-1″), 104.6 (Glc-1′), 81.4 (Glc-4′), 78.3 (Glc-5″), 77.9 (Glc-3″), 76.3 (Glc-3′), 75.2 (Glc-2′), 74.9 (Glc-2″), 74.3 (Glc-5′), 71.4 (Glc-4″), 63.8 (Glc-6′), 62.5 (Glc-6″). Ester moiety δ: 168.6 (C-α), 149.6 × 2 (C-3‴, C-5‴), 147.0 (C-γ), 139.7 (C-4‴), 126.6 (C-1‴), 115.8 (C-β), 106.9 × 2 (C-2‴, C-6‴), 56.8 × 2 (–OMe‴ ×2). 1H-NMR spectroscopic data (measured in MeOH-d4): aglycone moiety δ: 6.64 (2H, s, H-2a, H-6a), 6.58 (2H, s, H-2, H-6), 4.61 (1H, d, J = 5.5 Hz, H-7a), 4.48 (1H, d, J = 5.5 Hz, H-7), 4.18 (1H, dd, J = 9.0, 7.0 Hz, H-9), 4.15 (1H, dd, J = 9.0, 7.0 Hz, H-9a), 3.85 (6H, s, –OMea ×2), 3.81 (6H, s, -OMe ×2), 3.79 (1H, dd, J = 9.0, 4.5 Hz, H-9), 3.79 (1H, dd, J = 9.0, 4.5 Hz, H-9a), 3.00 (1H, m, H-8a), 2.95 (1H, m, H-8). Sugar moiety δ: 4.85 (overlapping, Glc-1′), 4.53 (1H, dd, J = 12.0, 6.0 Hz, Glc-6′), 4.48 (1H, dd, J = 12.0, 2.5 Hz, Glc-6′), 4.37 (1H, dd, J = 8.0 Hz, Glc-1″), 3.89 (1H, dd, J = 12.0, 2.5 Hz, Glc-6″), 3.66 (1H, dd, J = 12.0, 6.0 Hz, Glc-6″), 3.65 (overlapping, Glc-4′), 3.61 (overlapping, Glc-2′, Glc-3′), 3.60 (overlapping, Glc-5′), 3.36 (1H, m, Glc-5″), 3.35 (1H, t, J = 9.0 Hz, Glc-3″), 3.29 (1H, t, J = 9.0 Hz, Glc-4″), 3.23 (1H, dd, J = 9.0, 8.0 Hz, Glc-2″). Ester moiety δ: 7.52 (1H, d, J = 16.0 Hz, H-γ) 6.90 (2H, s, H-2‴, H-6‴), 6.31 (1H, d, J = 16.0 Hz, H-β), 3.88 (6H, s, –OMe‴ ×2).

Oxypetalumoside III (17)

Amorphous powder. [α]D19 −77 (c = 0.32, MeOH). HR-ESI-MS: m/z 941.3064 [M + Na]+ (Calcd for C44H54O21Na: 941.3055), 917.3069 [M−H] (Calcd for C44H53O21: 917.3079). UV λmax(MeOH) nm (log ε): 239 (sh), 328 (4.13). The 13C- and 1H-NMR spectroscopic data of the aglycone and sugar moieties were in good agreement with those of 16. The 13C- and 1H-NMR spectroscopic data of the ester moiety (measured in MeOH-d4) δ: 168.9 (C-α), 150.8 (C-4‴), 149.5 (C-3‴), 146.8 (C-γ), 127.7 (C-1‴), 124.2 (C-6‴), 116.6 (C-5‴), 115.4 (C-β), 111.6 (C-2‴), 56.5 (-OMe‴), δ: 7.52 (1H, d, J = 16.0 Hz, H-γ), 7.17 (1H, d, J = 2.0 Hz, H-2‴), 7.05 (1H, dd, J = 8.0, 2.0 Hz, H-6‴), 6.83 (1H, d, J = 8.0 Hz, H-5‴), 6.27 (1H, d, J = 16.0 Hz, H-β), 3.89 (3H, s, –OMe‴).

Conflict of Interest

The authors declare no conflict of interest.

Supplementary Materials

The online version of this article contains supplementary materials.

References
 
© 2021 The Pharmaceutical Society of Japan
feedback
Top