Camellianols AâG, Barrigenol-like Triterpenoids with PTP1B Inhibitory

Article Cite This: J. Nat. Prod. 2017, 80, 2874-2882

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Camellianols A−G, Barrigenol-like Triterpenoids with PTP1B Inhibitory Effects from the Endangered Ornamental Plant Camellia crapnelliana Juan Xiong,†,# Jiang Wan,†,‡,# Jie Ding,*,‡ Pei-Pei Wang,§ Guang-Lei Ma,† Jia Li,§ and Jin-Feng Hu*,† †

Department of Natural Products Chemistry, School of Pharmacy, Fudan University, Shanghai 201203, People’s Republic of China School of Chemical Engineering, Sichuan University of Science & Engineering, Zigong 643000, People’s Republic of China § State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, People’s Republic of China ‡

S Supporting Information *

ABSTRACT: Seven new naturally occurring barrigenol-like compounds, camellianols A−G (1−7), and 10 known triterpenoids were isolated from the twigs and leaves of the cultivated endangered ornamental plant Camellia crapnelliana. According to the ECD octant rule for saturated cyclohexanones, the absolute configurations of camellianols D (4) and E (5) were defined. The backbones of the remaining new isolates are assumed to have the same absolute configuration as compounds 4, 5, and harpullone (12). Compounds 2, 3, 9, 10, 13, and 16 exhibited inhibitory effects on the protein tyrosine phosphatase 1B (PTP1B) enzyme, with IC50 values less than 10 μM.

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habitat destruction, environmental contamination, overexploitation, and alien introduction, and other ecological changes, and, thus, they were recorded in the China Plant Red Data Book (CPRDB) as early as 1992.13 These include Camellia crapnelliana Tutcher, with the common name Crapnell’s camellia. It is a 5−7 m tall tree featuring rust-red trunk bark, thick leathery leaves, and solitary and beautiful terminal flowers.10 As an endangered plant,14 this species was first collected and described in 1903 by W. J. Tutcher from Mount Parker, Hong Kong, and only one tree was found at that time. Thereafter, the wild species has also been found in several locations in southeastern China, and now people can plant these as ornamentals.13 During a continuing search for new bioactive compounds from wild and/or cultivated rare and endangered plants endemic to China,3−8 seven new barrigenollike and 10 related pentacyclic triterpenoids were isolated and identified from C. crapnelliana collected at a Cantonese Botanical Garden. Reported herein are their isolation, structural elucidation, and inhibitory effects on the PTP1B enzyme.

ecently, a pioneering phylogenetic study of the terrestrial plants showed that nature-derived drugs are mainly produced by specific drug-productive plant families, and most endangered species are in those drug-producing families.1,2 Since 2013, special attention has been paid to the discovery of bioactive novel compounds from rare and endangered plants endemic to China. So far, several endangered conifers, e.g., Pinus dabeshanensis3 and Abies beshanzuensis,4 and the cultivated endangered ornamental Magnoliaceae plant Manglietia aromatic,5 together with a few rare Chloranthaceae plants, e.g., Chloranthus sessilifolius6 and Chloranthus oldhamii,7 and the rare cliff plant Oresitrophe rupif raga,8 have been investigated, and some of their secondary metabolites might potentially function as inhibitors of the protein tyrosine phosphatase 1B (PTP1B) enzyme.9 Camellia is the largest genus (about 280 species) in the family Theaceae, and more than 80% of the species are distributed in China.10 Camellia species have a long history of cultivation in Asian countries due to their significant commercial value as tea plants (e.g., C. sinensis), oil crops (e.g., C. oleifera), and attractive ornamentals due to their large and colorful flowers. Some species in this genus have been utilized as traditional Chinese medicines for their stomachic, anti-inflammatory, and expectorant properties.10,11 Phytochemically, flavonoids and triterpenoid saponins have been documented to be the major secondary metabolites of Camellia plants.12 Five Camellia species native to China are classified as threatened with extinction due to anthropogenic activities, e.g., © 2017 American Chemical Society and American Society of Pharmacognosy

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RESULTS AND DISCUSSION The water-suspended 90% MeOH extract of the twigs and leaves of C. crapnelliana (3.5 kg) was fractionated successively with petroleum ether, EtOAc, and n-BuOH. Further chromatographic separation of the EtOAc fraction afforded seven new (1−7) and 10 known (8−17) naturally occurring triterpenoids Received: March 21, 2017 Published: October 24, 2017 2874

DOI: 10.1021/acs.jnatprod.7b00241 J. Nat. Prod. 2017, 80, 2874−2882

Journal of Natural Products

Article

Figure 1. Structures of pentacyclic triterpenoids 1−17 from C. crapnelliana.

eton as A1-barrrigenol (8),15 which was confirmed by the H−1H COSY and HMBC spectroscopic data (Figure 2). The only difference was the presence of an acetyl group in compound 1, which was located at the HO-16 group via the HMBC cross-peaks from H-16 to C-15, C-28, and the carbonyl carbon (Figure 2). By analysis of vicinal coupling constants of the key protons (Table 2) and ROE correlations (Figure 3), the relative configuration of 1 could be readily determined. The magnitudes of JH‑2β/H‑3 (11.5 Hz), JH‑5/H‑6β (11.4 Hz), JH‑9/H‑11β (11.5 Hz), JH‑18/H‑19α (11.4 Hz), and JH‑21α/H‑22 (12.2 Hz) indicated that these protons are all in axial positions. The ROE correlations (Figure 3) unequivocally confirmed that both compounds 1 and 8 possess the same relative configurations. In particular, the ROE correlations of Me-26/H-15, H-15/H-16, H-15/H2-28, H2-28/H-22, and H-22/Me-30 established that H-15, H-16, and H-22 are β-oriented. Therefore, compound 1 (camellianol A) was characterized as 16α-acetoxy3β,15α,22α,28-tetrahydroxyolean-12-ene. The negative mode HRESIMS data of camellianol B (2) gave an [M − H + HCOOH]− ion at m/z 659.4153, corresponding to a molecular formula of C37H58O7. Its 1H and 13C NMR data resembled those of 1 (Tables 1 and 2), indicating the same pentahydroxylated triterpenoid skeleton. However, the 1H NMR spectrum of 2 displayed additional resonances corresponding to two vinylic methyl groups [δ 1.85 (3H, br s, Me-5′) and 1.99 (3H, dq, J = 7.1, 1.6 Hz, Me-4′)] and an olefinic proton at δ 6.14 (1H, q, J = 7.1 Hz, H-3′), together with the corresponding 13C NMR resonances at δ 168.9 (C-1′), 140.4 (C-3′), 127.2 (C-2′), 20.5 (C-5′), and 15.7 (C-4′) (Table 1). These resonances could be assigned to an angeloyl group, as substantiated by the HMBC cross-peaks from H-3′ to C-1′/C4′/C-5′, Me-4′ to C-2′, and Me-5′ to C-1′/C-3′ (Figure 2), and the geometric configuration (Z) of the double bond in the angeloyloxy moiety was corroborated by the ROE correlations of H-3′ with both Me-4′ and Me-5′ (Figure 3). The deshielded chemical shift (Δδ = 1.51 ppm) of H-22 when compared with

(Figure 1). The known structures were identified as A1barrigenol (8),15,16 22-O-angeloyl-A1-barrigenol (9),16 camelliagenin A (10),16 16-O-acetylcamelliagenin A (11),17 harpullone (12),18 3β,11α,13β-trihydroxyolean-12-one (13),19 βamyrin (14),20,21 α-amyrin (15),20,21 lupeol (16),22 and 3β,20-dihydroxylupane (17)23,24 by comparing their physicochemical properties and spectroscopic data with reported values. This is the first report of the presence of triterpenoids 11 and 12 in the Camellia genus. The 13C NMR data and absolute configuration of 12 are reported here for the first time. The molecular formula of compound 1, C32H52O6, was deduced from the HRESIMS sodium adduct ion at m/z 555.3665 [M + Na]+ and 13C NMR data (Table 1). The infrared absorptions at 3425 and 1725 cm−1 correspond to hydroxy and ester carbonyl functionalities, respectively. In the upfield region of the 1H NMR spectrum (Table 2), resonances for seven tertiary methyl groups at δ 0.79 (3H, s, Me-24), 0.94 (3H, s, Me-29), 0.95 (6H, s, Me-25 and Me-30), 0.99 (3H, s, Me-23), 1.02 (3H, s, Me-26), and 1.37 (3H, s, Me-27) were evident. This, together with an olefinic proton at δ 5.40 (1H, t, J = 3.5 Hz, H-12), is reminiscent of an olean-12-ene pentacyclic triterpenoid framework.25 Resonances reminiscent of an oxymethylene group [δ 3.43 (1H, d, J = 11.3 Hz) and 3.70 (1H, dd, J = 11.3, 7.6 Hz), H2-28] and four oxymethine resonances at δ 3.24 (1H, ddd, J = 11.5, 6.0, 4.2 Hz, H-3), 3.90 (1H, ddd, J = 12.2, 7.6, 5.9 Hz, H-22), 4.32 (1H, dd, J = 6.0, 3.8 Hz, H-15), and 5.72 (1H, d, J = 3.8 Hz, H-16), along with the resonance of an acetyl methyl at δ 2.18 (3H, s), were also readily distinguished. Analysis of the 13C (Table 1), DEPT-135, and HSQC NMR data indicated that 1 possesses 32 carbons, comprising eight methyl, eight methylene (one oxygenated at δ 73.0, C-28), eight methine [one olefinic at δ 125.9 (C-12) and four oxygenated at δ 67.2 (C-15), 75.1 (C-16), 76.7 (C-22), and 78.9 (C-3)], and seven quaternary (one olefinic at δ 141.7, C-13) carbons and an acetyl carbonyl carbon at δ 173.2. These NMR data suggested that 1 is a polyhydroxylated triterpenoid with the same 3,15,16,22,28-pentahydroxyolean-12-ene skel-

1

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Table 1. 13C NMR Dataa (δ in ppm, in CDCl3, 125 MHz) of Triterpenoids 1−7 and 12

a

position

1

2

3

4

5

6

7

12

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 Ang-1′ Ang-2′ Ang-3′ Ang-4′ Ang-5′ CH3CO− CH3CO−

38.8 27.2 78.9 38.7 54.8 18.5 36.1 41.3 46.8 37.0 23.5 125.9 141.7 47.7 67.2 75.1 43.6 42.6 46.0 31.3 44.4 76.7 28.0 15.5 15.6 17.2 19.7 73.0 33.4 24.8

38.6 27.2 78.9 38.8 54.8 18.5 36.2 41.2 46.9 37.0 23.6 126.8 141.1 47.2 68.3 75.6 44.5 41.1 46.0 31.5 41.5 70.3 28.0 15.6 15.9 17.2 19.7 64.1 33.2 24.5 168.9 127.2 140.4 15.7 20.5 171.6 21.7

38.7 27.2 78.8 38.8 54.6 18.6 34.6 40.9 46.7 37.0 23.4 126.4 141.2 46.2 71.6 72.5 45.1 41.2 46.5 31.5 41.7 70.9 28.0 15.6 15.5 17.1 21.1 62.7 32.9 24.6 169.3 127.6 138.9 15.8 20.6 169.9 21.7

39.5 34.2 217.4 47.1 54.6 19.9 34.1 41.1 45.9 36.7 23.6 125.4 141.9 47.3 71.4 69.7 44.0 42.8 46.8 31.2 44.9 76.1 26.5 21.4 15.4 17.1 20.8 71.8 33.0 24.8

39.5 34.1 217.7 47.4 54.9 19.8 35.5 41.2 46.1 36.8 23.7 125.7 141.8 47.8 67.3 75.1 43.6 42.8 45.9 31.4 44.4 76.8 26.4 21.4 15.4 17.1 19.5 73.1 33.4 24.7

38.7 27.2 78.9 38.7 54.8 18.5 36.1 40.9 46.8 37.0 23.5 124.4 144.0 47.2 67.9 78.2 40.0 42.4 47.2 30.7 36.2 29.7 28.0 15.6 15.6 17.4 20.1 70.2 32.9 24.0

38.7 27.2 78.9 38.7 54.8 18.5 36.0 40.9 46.7 37.0 23.7 125.6 142.3 47.4 67.4 71.9 43.6 42.1 46.7 31.1 45.2 72.4 28.0 15.6 15.6 17.4 20.1 68.4 33.0 24.6 167.4 126.9 139.9 15.8 20.7

39.4 34.1 217.7 47.3 54.9 19.8 35.4 40.9 46.7 36.7 23.7 124.6 143.0 47.7 67.2 72.1 43.8 42.9 45.9 31.2 45.3 76.6 26.5 21.5 15.4 17.2 20.0 71.4 33.0 24.7

170.3 21.8

173.2 22.0

173.2 22.0

Assignments were made by a combination of 1D and 2D NMR experiments.

that of compound 1 indicated that the angeloyloxy moiety was located at C-22, which was confirmed by the HMBC crosspeaks from H-22 to C-1′, C-18, C-16, and C-28 (Figure 2). The α-equatorial orientation of this angeloyloxy group was deduced from the large vicinal coupling constant (12.4 Hz) of JH‑22/H‑21α and from the ROE correlations of H-22/H-18 and H-22/Me-30 (Figure 3). Accordingly, the structure of compound 2, camellianol B, was defined as 16α-acetoxy-22α-angeloyloxy3β,15α,28-trihydroxyolean-12-ene. Compound 3 has the same molecular formula (C37H58O7) as 2 based on the HRESIMS data. Their NMR data showed a close resemblance (Tables 1 and 2). Major differences occurred in the vicinity of C-15 and C-16, implying that the C-16 acetoxy substituent in 2 was located at C-15 in 3. This inference was supported by the HMBC cross-peaks from H-15 (δ 5.10, d, J = 3.9 Hz) to C-27 (δ 21.7) and the acetoxy carbonyl carbon (δ 169.9) (Figure 2). The relative configuration of 3, including the (Z)-configuration of the double bond in the angeloyl substituent, was found to be the same as that of 2 by J-based configuration analysis (Table 2) and ROESY data (Figure S2 in Supporting Information). Thus, the structure of 3, camellianol

C, was defined as 15α-acetoxy-22α-angeloyloxy-3β,16α,28trihydroxyolean-12-ene. Camellianols D (4) and E (5) have the same molecular formula, C32H50O6, as determined by their HRESIMS and 13C NMR data, requiring that each has one more index of hydrogen deficiency than 1. Consistent with this, the 1H and 13C NMR spectroscopic data of 4 revealed the presence of a ketocarbonyl group (δ 217.4) rather than the C-3 oxymethine group (δH 3.24, δC 78.9) in compound 1 (Tables 1 and 3). The presence of the C-3 carbonyl group in 4 was corroborated by the HMBC cross-peaks from H-2β (δ 2.58), Me-23 (δ 1.11), and Me-24 (δ 1.05) to this carbonyl carbon (Figure 2). The 15α-acetoxy group was verified by the HMBC cross-peaks from the oxymethine proton (H-15, δ 5.38, d, J = 3.8 Hz) to the ester carbonyl carbon (δ 170.3) and from Me-27 (δ 1.54) to C-15 (δ 71.4) (Figure 3). Similar to 1, H-15, H-16, and H-22 were all βoriented based on their vicinal proton coupling constants (Table 3) and ROE data (Figure S2, Supporting Information). Comparison of the NMR data of 5 with those of 4 (Tables 1 and 3) suggested that the C-15 acetoxy group in 4 shifted to C16 in 5, as corroborated by 2D NMR (HSQC, HMBC, and 2876



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Table 2. 1H NMR Dataa (δ in ppm, J in Hz, 400 MHz) of Triterpenoids 1−3 and 7 in CDCl3 position 1α 1β 2α 2β 3 5 6α 6β 7α 7β 9 11a 11b 12 15 16 18 19α 19β 21α 21β 22 23 24 25 26 27 28 29 30 CH3CO− Ang-3′ Ang-4′ Ang-5′ OH-3 OH-15 OH-16 OH-22 OH-28 a

1 1.00 1.66 1.59 1.63 3.24 0.75 1.56 1.41 1.71 1.69 1.56 1.94 1.91 5.40 4.32 5.72 1.95 2.15 1.13 1.25 1.54 3.90 0.99 0.79 0.95 1.02 1.37 3.43 3.70 0.94 0.95 2.18

m m m m ddd (11.5, 6.0, 4.2) br d (11.4) m m m m br d (11.5) m m t (3.5) dd (6.0, 3.8) d (3.8) dd (12.4, 4.3) dd (12.4, 12.1) dd (12.4, 4.3) dd (12.8, 12.2) dd (12.8, 5.9) ddd (12.2, 7.6, 5.9) s s s s s br d (11.5) dd (11.5, 7.0) s s s

1.35 d (6.0) 1.86 d (overlapped)

2

3

1.00 m 1.66 m 1.58 m 1.62 m 3.24 ddd (11.5, 5.8, 4.5) 0.74 br d (11.0) 1.53 m 1.37 m 1.69 m 1.65 m 1.54 br d (10.8) 1.93 m 1.90 m 5.55 t (3.3) 4.01 dd (4.1, 3.1) 5.25 d (4.1) 2.61 dd (14.1, 4.5) 2.27 dd (14.1, 13.8) 1.24 dd (13.8, 4.5) 1.82 dd (12.4, 12.4) 1.51 dd (12.4, 6.0) 5.41 dd (12.4, 6.0) 0.98 s 0.78 s 0.95 s 1.00 s 1.33 s 3.18 dd (15.0, 5.6) 3.41 dd (15.0, 6.1) 0.99 s 1.05 s 2.17s 6.14 q (7.1) 1.99 dq (7.1, 1.6) 1.85 br s 1.56 d (overlapped) 1.86 d (overlapped)

1.00 1.66 1.58 1.60 3.24 0.73 1.51 1.40 1.69 1.65 1.57 1.92 1.91 5.55 5.10 3.90 2.65 2.37 1.16 2.35 1.44 5.45 1.00 0.78 0.94 1.01 1.53 3.13 3.37 0.95 1.04 2.10 6.11 1.99 1.88 1.58

m m m m br d (10.2) br d (11.4) m m m m br d (10.0) m m t (3.6) d (3.9) br s dd (14.0, 4.7) dd (14.0, 12.8) dd (12.8, 4.7) dd (12.8, 12.5) dd (12.8, 5.4) dd (12.5, 5.4) s s s s s dd (11.0, 5.1) dd (11.0, 10.5) s s s q (7.2) dq (7.2, 1.6) br s d (overlapped)

1.92 br s 3.15 d (7.6) 3.46 br d (overlapped)

3.18 dd (overlapped)

7 1.00 m 1.64 m 1.58 m 1.65 m 3.23 br d (10.5) 0.76 br d (11.6) 1.61 m 1.41 m 1.77 m 1.67 m 1.55br d (10.2) 1.92m 1.90 m 5.41 t (3.2) 3.97 dd (8.2, 3.9) 4.26 dd (4.3, 3.9) 2.27 dd (13.9, 6.8) 2.27 dd (13.9, 13.8) 1.12 dd (13.8, 4.8) 1.81 dd (12.6, 12.6) 1.61 dd (overlapped) 4.00 ddd (12.6, 6.1, 5.0) 1.00 s 0.80 s 0.95 s 1.03 s 1.36 s 3.73 d (11.6) 4.22 d (11.6) 0.95 s 0.95 s 6.13 2.01 1.92 1.34 2.54 2.60 2.43

q (7.2) br d (7.2) br s d (6.0) d (8.2) d (4.3) d (5.0)


Assignments were made by a combination of 1D and 2D NMR experiments.

ROESY) experiments (Figures S1 and S2, Supporting Information). The chemical shift of Me-27 in 4 was significantly deshielded (ΔδH = 0.17 ppm) when compared with compound 5. A similar difference was also observed when comparing the proton NMR resonances of triterpenoids 2 and 3 (Me-27 in 2: δH 1.33, in 3: δH 1.53). Based on the above evidence, the structures of 4 and 5 were defined as 15α-acetoxy-16α,22α,28trihydroxyolean-12-en-3-one and 16α-acetoxy-15α,22α,28-trihydroxyolean-12-en-3-one, respectively. The formation of a mixture of regioisomers via an intramolecular transacetylation process has been reported for salvinorins D and E.26 The dynamic equilibrium between these two neoclerodane diterpenoids occurred via a process of intramolecular transacetylation, which is stereochemically favored by the cofacial 1α-axial and 2α-equatorial orientation of the O-acetyl and vicinal hydroxy group in the same ring.26 In this study, compound 2 and its regioisomer 3, as well as compound 4 and its regioisomer 5, are relatively stable during

Figure 2. 1H−1H COSY and HMBC correlations of triterpenoids 1− 4.

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Table 3. 1H NMR Dataa (δ in ppm, J in Hz, 400 MHz) of Triterpenoids 4−6 in CDCl3 position

4

5

1.47 m 1.90 m 2.38 ddd (15.9, 6.8, 3.7) 2.58 ddd (15.9, 10.7, 7.1)

1.44 m 1.91 m 2.38 ddd (15.9, 6.9, 3.7) 2.56 ddd (15.9, 11.0, 7.3)

3 5 6α 6β 7α 7β 9 11a 11b 12 15

1.34 1.53 1.36 1.81 1.72 1.64 1.97 1.94 5.44 5.38

1.34 1.51 1.36 1.81 1.70 1.64 1.98 1.93 5.43 4.33

16

4.56 d (3.8)

5.73d (3.6)

18

1.99 dd (12.8, 4.5)

1.97 dd (12.7, 4.7)

19α

2.33 dd (12.9, 12.8)

2.15 dd (12.7, 12.7)

19β


1.13 dd (12.3, 5.2)

3.24br d (10.4) 0.75 br d (12.3) 1.60 m 1.42 m 1.76 m 1.67 m 1.58 br d (10.8) 1.91 m 1.89 m 5.39 t (3.9) 4.06 dd (6.3, 4.3) 3.95 dd (4.3, 3.5) 2.06 dd (13.8, 3.3) 2.16 dd (13.8, 12.4) 1.07 br d (12.4)

1.25 dd (12.9, 12.2) 1.54 dd (overlapped) 4.01 dd (12.2, 5.4) 1.11 s 1.05 s 1.07 s 1.06 s 1.54 s 3.37 d (11.0) 3.76 d (11.0) 0.95 s 0.95 s 2.12 s

1.25 dd (12.7, 12.3) 1.52 dd (12.7, 5.2)

1.25 m 1.76 m

3.90 1.09 1.06 1.09 1.07 1.37 3.45 3.70 0.95 0.95 2.19

1.31 1.00 0.79 0.95 1.00 1.37 3.22 3.37 0.91 0.91

1α 1β 2α 2β

Figure 3. Diagnostic ROE correlations of triterpenoids 1 and 2.

the purification and NMR data acquisition, and even during extended storage or in attempts of their recrystallization from CH2Cl2 or MeOH. The spontaneous migration of the O-acyl group from C-15 to C-16 and vice versa was not observed. Camellianol F (6) showed a sodium adduct ion at m/z 497.3605 (calcd 497.3601) in the HRESIMS, corresponding to the molecular formula of C30H50O4 in combination with the 13 C NMR data. Its 1H and 13C NMR data (Tables 1 and 3) were comparable to those of A1-barrrigenol (8),15 implying the presence of a common olean-12-ene triterpenoid skeleton. However, compound 6 has only three oxymethine groups [δH 3.24 (1H, br d, J = 10.4 Hz), δC 78.9; δH 4.06 (1H, dd, J = 6.3, 4.3 Hz), δC 67.9; δH 3.95 (1H, dd, J = 4.3, 3.5 Hz), δC 78.2]. These three oxymethines were unambiguously assigned to C-3, C-15, and C-16, respectively, by HSQC and HMBC experiments. The diagnostic HMBC cross-peaks from Me-27 (δ 1.37) and H-16 (δ 3.95) to C-15 (δ 67.9) corroborated the presence of the 15,16-diol group (Figure S1, Supporting Information). The ROE correlations of Me-26/H-15, H-15/H-16, H-16/H228, and H2-28/H-15 (Figure S2, Supporting Information), along with the small vicinal coupling constant (J H‑15/H‑16 = 4.3 Hz) (Table 3), necessitated the α-orientation for both 15-OH and 16-OH. Thus, the structure of compound 6, camellianol F, was defined as a new naturally occurring barrigenol-like triterpenoid, 3β,15α,16α,28-tetrahydroxyolean-12-ene. This structure was previously reported as a synthesized product emanating from entagenic acid via LiAlH4 reduction.27 With an [M + Na]+ ion at m/z 595.3972 in the HRESIMS, camellianol G (7) has the same molecular formula, C35H56O6, as that of A1-barrigenol 22-angelate (9).16 Comparison of their NMR data suggested that 7 also featured a characteristic olean12-ene-type triterpenoid substituted with four hydroxy groups and one angeloyl moiety. However, compared with the corresponding resonance (δ 5.47) in 9, the chemical shift of H-22 in 7 was shielded to δ 4.00, whereas resonances of H2-28 were found to be more deshielded than those in 9 (δ 3.73/4.22 in 7; 3.05/3.31 in 9). This indicated that the angeloyloxy residue in compound 7 was located at C-28 and confirmed by the HMBC cross-peaks from H2-28 to C-1′ (δ 167.4) (Figure

20β 21α 21β 22 23 24 25 26 27 28 29 30 CH3CO− OH-3 OH-11 OH-12 OH-15 OH-16 OH-21 OH-22 OH-28

br d (11.5) m m m m br d (10.8) m m br s d (3.8)

6

br d (11.5) m m m m dd (11.2, 5.7) m m t (3.9) d (3.6)

dd (12.3, 5.2) s s s s s d (11.6) d (11.6) s s s

1.01 m 1.65 m 1.59 m 1.63 m

m; 1.24 m s s s s s br d (10.6) br d (10.6) s s

1.32 br s

ND

ND ND

ND

2.20 d (6.3) 2.37 d (3.5)

ND ND

3.20 br s

a

Assignments were made by a combination of 1D and 2D NMR experiments. ND: not detectable.

S1, Supporting Information). In addition, the four hydroxy groups located at C-3, C-15, C-16, and C-22, respectively, were all confirmed via the HMBC data. Its relative configuration was the same as that of 9 by inspection of proton−proton coupling constants (Table 2) and ROESY data (Figure S2, Supporting Information). Compound 7, camellianol G, was therefore identified as 28-angeloyloxy-3β,15α,16α,22α-tetrahydroxyolean-12-ene. This compound has been reported as an artifactual sapogenin isolated from the saponin hydrolysates of two 2878



Article

Harpullia plants cultivated in Egypt.28 Herein, compound 7 was isolated and identified as a new naturally occurring barrigenollike sapogenin. The absolute configurations of the new barrigenol-like triterpenoids were determined by X-ray crystallographic and/ or electronic circular dichroism (ECD) data. The (5R,8R,9R,10R,14S,15R,16S,17S,18S,22S) absolute configuration of the known harpullone (12) was assigned by Cu Kα X-ray crystallographic analysis [Flack parameter: 0.03(3)]29 (Figure 4). Thus, the absolute configurations of the acetyl

3, 7, 10, 11, and 16 were also active, with IC50 values less than or around 10 μM. Among the tested compounds, only β-amyrin (14), the oleanane-type triterpenoid bearing just one OH group, was found to be totally inactive (IC50 > 100 μM). A comparison of the inhibitory effects among the three pentacyclic triterpenoid analogues 14−16 (IC50s: >100, 19.26, 3.68 μM, respectively) implied that the influence of the triterpenoid skeleton on the PTP1B inhibitory activity appeared to be lupene > ursene > oleanene type. The PTP1B inhibitory effects of the oleanane-type triterpenoids were found to be enhanced with the introduction of diverse oxygen-containing groups. Compound 2, with an angeloyloxy group at C-22 when compared to 1, was about 10-fold more potent than 1 (IC50: 47.35 μM). Such a difference could also be found between compounds 8 (IC50: 16.79 μM) and 9, suggesting that the introduction of an angeloyloxy group at C-22 would be beneficial for the PTP1B inhibitory activity. In contrast, the activity was only slightly improved when the angeloyloxy group was attached to C-28, i.e., comparing 8 with 7. The initial structure−activity relationships (SAR) are summarized as shown in Figure 5. It is worth mentioning that among the known compounds only lupeol (16) has been previously reported as a PTP1B inhibitor.31

Figure 4. ORTEP drawing of harpullone (12).

derivatives 4 and 5 of harpullone were found to be the same as harpullone by analysis of their ECD spectra. A diagnostic positive Cotton effect at 289 nm due to the n−π* transition of the C-3 carbonyl group was observed in the ECD spectra of both triterpenoids 4 and 5, from which the absolute configuration of C-5 could be readily established as R by application of the cyclohexanone octant rule.30 The backbones of the remaining new isolates are assumed to have the same absolute configuration as compounds 4, 5, and 12. All the isolates were subjected to bioassay protocols3,5,7a to determine their PTP1B inhibitory effects, a potential therapeutic target for type 2 diabetes mellitus (T2DM).9 As summarized in Table 4, the tetra- and trihydroxylated oleananetype triterpenoids 9 (IC50 = 2.56 μM) and 13 (IC50 = 1.34 μM) were found to be most potent, similar to the positive control3,5,7a (oleanolic acid, IC50 = 3.32 μM). Compounds 2,

Figure 5. Initial SAR analysis of barrigenol-like triterpenoids with PTP1B inhibition.

None of the isolates showed cytotoxicity against human hepatoma L02 cells at 10 μM (cell viabilities >90%). Only compounds 8, 10, 11, and 12 showed some cytotoxic effects (cell viabilities 100 19.26 ± 0.49 3.68 ± 0.21 12.44 ± 1.27 3.32 ± 0.19

a

The purity of the tested compounds ranged from 95.5% to 99.5% as determined by analytical HPLC with ELSD detection. bValues are expressed as mean ± SD of three replicates. cPositive control (purity >98%). 2879



Article

HPLC (MeOH/H2O, 80:20) afforded compounds 4 (2.0 mg, tR = 25.2 min) and 5 (4.0 mg, tR = 22.7 min). Triterpenoid 17 (60.0 mg) was recrystallized from Fr.5D (398.0 mg), and the mother liquid was separated on Sephadex LH-20 (MeOH) and RP-HPLC (MeOH/H2O, 95:5; tR = 19.5 min) to give compound 13 (7.6 mg). Compound 12 (3.2 mg) was purified from Fr.5E (207.1 mg) by GPC on Sephadex LH-20 (MeOH) followed by RP-HPLC purification (MeOH/H2O, 84:16; tR = 12.0 min). Camellianol A (16α-acetoxy-3β,15α,22α,28-tetrahydroxyolean12-ene, 1): white, amorphous powder; [α]21D +17 (c 0.2, CHCl3); UV (CHCl3) λmax (log ε) 239 (3.89), 272 (3.72) nm; IR (KBr) νmax 3425, 2962, 2924, 2850, 1725, 1634, 1433, 1380 1262, 1095, 1020, 811 cm−1; 1H and 13C NMR data, see Tables 1 and 2; HRESIMS m/z 555.3665 [M + Na]+ (calcd for C32H52NaO6, 555.3656, Δ = +1.6 ppm). Camellianol B (16α-acetoxy-22α-angeloyloxy-3β,15α,28-trihydroxyolean-12-ene, 2): white, amorphous powder; [α]21D −15 (c 0.2, CHCl3); UV (CHCl3) λmax (log ε) 239 (4.13) nm; IR (KBr) νmax 3441, 2955, 2924, 2853, 1726, 1680, 1640, 1459, 1376, 1259, 1240, 1022, 801, 760 cm−1; 1H and 13C NMR data, see Tables 1 and 2; HRESIMS m/z 659.4153 [M − H + HCOOH]− (calcd for C38H59O9, 659.4154, Δ = −0.1 ppm). Camellianol C (15α-acetoxy-22α-angeloyloxy-3β,16α,28-trihydroxyolean-12-ene, 3): white, amorphous powder; [α]21D −2 (c 0.2, CHCl3); UV (CHCl3) λmax (log ε) 239 (4.32), 268 (3.84) nm; IR (KBr) νmax 3436, 2962, 2920, 2853, 1716, 1680, 1640, 1460, 1379, 1242, 1035, 820, 760 cm−1; 1H and 13C NMR data, see Tables 1 and 2; HRESIMS m/z 637.4084 [M + Na]+ (calcd for C37H58NaO7, 637.4075, Δ = +1.5 ppm). Camellianol D (15α-acetoxy-16α,22α,28-trihydroxyolean-12-en3-one, 4): white, amorphous powder; [α]21D +14 (c 0.1, CHCl3); UV (CHCl3) λmax (log ε) 250 (4.09) nm; ECD (c 5.3 × 10−3 M, MeOH) λmax (Δε) 287 (+1.19) nm; IR (KBr) νmax 3440, 2964, 2922, 2850, 1715, 1634, 1459, 1377, 1252, 1043, 762 cm−1; 1H and 13C NMR data, see Tables 1 and 3; HRESIMS m/z 553.3505 [M + Na]+ (calcd for C32H50NaO6, 553.3500, Δ = +0.7 ppm). Camellianol E (16α-acetoxy-15α,22α,28-trihydroxyolean-12-en3-one, 5): white, amorphous powder; [α]21D +26 (c 0.1, CHCl3); UV (CHCl3) λmax (log ε) 240 (4.20), 267 (3.97) nm; ECD (c 3.2 × 10−3 M, MeOH) λmax (Δε) 289 (+0.77) nm; IR (KBr) νmax 3417, 2950, 2922, 2850, 1705, 1649, 1455, 1375, 1256, 1027, 760 cm−1; 1H and 13 C NMR data, see Tables 1 and 3; HRESIMS m/z 553.3522 [M + Na]+ (calcd for C32H52NaO6, 553.3500, Δ = +4.0 ppm). Camellianol F (3β,15α,16α,28-tetrahydroxyolean-12-ene, 6): white, amorphous powder; [α]21D +19 (c 0.2, MeOH); UV (MeOH) λmax (log ε) 201 (4.43) nm; (KBr) νmax 3411, 2962, 2925, 1850, 1640, 1460, 1379, 1257, 1025, 805 cm−1; 1H and 13C NMR data, see Tables 1 and 3; HRESIMS m/z 497.3606 [M + Na]+ (calcd for C30H50NaO4, 497.3601, Δ = +0.9 ppm). Camellianol G (28-angeloyloxy-3β,15α,16α,22α-tetrahydroxyolean-12-ene, 7): white, amorphous powder; [α]21D +25 (c 0.1, CHCl3); UV (CHCl3) λmax (log ε) 239 (4.42), 268 (4.05) nm; IR (KBr) νmax 3405, 2962, 2926, 2856, 1718,1640, 1467, 1371, 1235, 1160, 1070, 1041, 920, 850, 781 cm−1; 1H and 13C NMR data, see Tables 1 and 2; HRESIMS m/z 595.3972 [M + Na]+ (calcd for C35H56NaO6, 595.3969, Δ = +0.5 ppm). Harpullone (15α,16α,22α,28-tetrahydroxyolean-12-en-3-one, 12): colorless needles from MeOH−CH2Cl2, mp 263−264 °C; [α]21D +49 (c 0.3, EtOH) [ref 18 [α]30D +21.3 (c 0.24, EtOH)]; UV (EtOH) λmax (log ε) 239 (4.38) nm; ECD (c 1.8 × 10−3 M, MeOH) λmax (Δε) 286 (+1.98) nm; IR (KBr) νmax 3405, 2956, 2920, 2853, 1705, 1675, 1640, 1417, 1372, 1320, 1280, 1118, 1070, 1033, 925, 872 cm−1; 1H NMR δ 0.94, 0.95, 1.04, 1.06, 1.07, 1.11, 1.37 (3H each, s, H3-30, 29, 24, 26, 25, 23, 27), 2.26 (1H, dd, J = 13.7, 13.6 Hz, H-19), 2.40 (1H, ddd, J = 15.8, 7.1, 3.7, 3.7 Hz, H-2), 2.55 (1H, ddd, J = 15.7, 10.8, 7.5 Hz, H-2) 3.34 (1H, d, J = 10.7 Hz, H-28), 3.66 (1H, dd, J = 10.6, 6.1 Hz, H-28), 4.00 (1H, m, H-22), 4.11 (1H, dd, J = 8.3, 4.7 Hz, H-15), 4.48 (1H, dd, J = 4.5, 3.7 Hz, H-16), 5.37 (1H, t, J = 4.0 Hz, H12), 2.83 (1H, d, J = 8.4 Hz, OH-15), 3.03 (1H, br s, OH-16), 3.22

exploration of the therapeutic potential of these polyhydroxylated oleanenes as well as the title plant in T2DM.

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EXPERIMENTAL SECTION

General Experimental Procedures. Optical rotations were recorded on a Rudolf Autopol IV automatic polarimeter. UV spectra were measured on a Hitachi U-2900E spectrophotometer. ECD spectra were recorded on a JASCO-810 spectropolarimeter. IR measurements were performed on a Nicolet Is5 FT-IR spectrometer. NMR spectra (in CDCl3) were recorded on a Bruker Avance III 400 MHz or 600 MHz spectrometer, and the chemical shifts (δ) are given in ppm with reference to the solvent signals. HRESIMS data were acquired on an AB Sciex Triple TOF 5600 spectrometer. Semipreparative HPLC was conducted on a Waters e2695 system equipped with a Cosmosil C18 column (5 μm, 250 × 10 mm) at a flow rate of 3.0 mL/min. Column chromatography (CC) was carried out using MCI gel CHP20P (75−150 μm, Mitsubishi Chemical Industries, Japan), silica gel (200−300 mesh, Ji-Yi-Da Silysia Chemical Ltd., Qingdao, PR China), and Sephadex LH-20 (GE Healthcare BioSciences AB, Sweden). TLC analysis was conducted on precoated silica gel GF254 plates (0.25 mm thick, Kang-Bi-Nuo Silysia Chemical Ltd., Yantai, PR China). Spots were visualized by 10% (v/v) H2SO4/EtOH reagent. Plant Material. The twigs and leaves of C. crapnelliana were harvested, with authorization, from the Foshan Botanical Garden, Guangdong Province (Cantonese), China, in November 2014. The plant was identified by Mr. Huan Ke at Foshan Municipal Forestry Research Institute. A voucher herbarium specimen (No. 20141120) has been deposited at the Department of Natural Product Chemistry, School of Pharmacy, Fudan University, PR China. Extraction and Isolation. The powerded twigs and leaves of C. crapnelliana (3.5 kg) were percolated with 90% MeOH (6 × 6 L) at ambient temperature and concentrated in vacuo. The resultant dark green residue (237 g, semidry) was suspended in H2O (1.2 L) and extracted successively with petroleum ether (3 × 1.2 L), EtOAc (3 × 1.2 L), and n-BuOH (3 × 1.2 L). The EtOAc-soluble extract (13.1 g) was fractionated on an MCI column with a stepwise gradient elution of MeOH/H2O (50:50 → 70:30 → 85:15 → 100:0), and eight fractions (Fr.1−Fr.8) were collected. Only Fr.4−Fr.6 displayed PTP1B inhibitory activities and were later found to be rich in triterpenoids as detected by TLC via the Liebermann−Burchard color reaction. Fr.4 (1.1 g) was separated over silica gel (CH2Cl2/EtOAc, 10:1 → 5:1 → 1:1 → 0:1) to give five subfractions, Fr.4A−4E. Subfraction Fr.4C (91.0 mg) was separated by gel permeation chromatography (GPC) on Sephadex LH-20 (MeOH), followed by semipreparative RP-HPLC (MeOH/H2O, 85:15), to afford compound 10 (2.2 mg, tR = 16.8 min). Fr.4D (443.6 mg) was further fractionated by Sephadex LH-20 with MeOH, and five fractions (Fr.4D-1−Fr.4D-5) were obtained. Fr.4D-2 (71.0 mg) was purified by semipreparative HPLC (MeCN/ H2O, 75:25) to afford compound 1 (5.0 mg, tR = 9.6 min). Purification of Fr.4D-4 (75.0 mg) by RP-HPLC (MeOH/H2O, 88:12) gave compounds 6 (1.7 mg, tR = 13.8 min) and 8 (7.0 mg, tR = 11.0 min). Fr.6 (1.8 g) was fractionated by GPC over Sephadex LH-20 with CH2Cl2/MeOH (2:1) to give fractions Fr.6A−6E. Separation of Fr.6E (630.0 mg) over silica gel with petroleum ether/EtOAc (20:1 → 5:1) and semipreparative RP-HPLC (MeOH) afforded compounds 14 (2.3 mg, tR = 30.3 min), 15 (1.2 mg, tR = 33.6 min), and 16 (0.8 mg, tR = 25.7 min). Fr.5 (3.1 g) was chromatographed over a silica gel column (petroleum ether/EtOAc, 10:1 → 5:1 → 1:1 → 0:1) to give six fractions, Fr.5A−5F. Fr.5B (612.0 mg) was rechromatographed by silica gel with petroleum ether/EtOAc (3:1), and four subfractions (Fr.5B-1−Fr.5B-4) were obtained. Triterpenoid 3 (2.0 mg, tR = 25.0 min) was isolated from Fr.5B-1 (44.0 mg) by semipreparative RPHPLC (MeCN/H2O, 60:40). By employing the same RP-HPLC purification system (MeCN/H2O, 80:20), compounds 2 (2.1 mg, tR = 19.9 min) and 9 (13.8 mg, tR = 17.4 min) were purified from Fr. 5B-2 (73.0 mg), whereas compounds 7 (2.7 mg, tR = 19.6 min) and 11 (7.0 mg, tR = 13.8 min) were obtained from Fr. 5B-3 (36.0 mg). Purification of the subfraction 5B-4 (33.0 mg) by semipreparative RP2880



Article

(1H, br s, OH-28); 13C NMR data, see Table 1; ESIMS m/z 511 [M + Na]+, 533 [M − H + HCOOH]−. X-ray Crystal Data of 12. C30H48O5·1/2CH2Cl2, M = 531.14, monoclinic, space group P1211, a = 9.8304(3) Å, b = 7.6333(2) Å, c = 20.2122(6) Å, α = 90°, β = 102.819(2)°, γ = 90°, V = 1478.897(7) Å3, Z = 2, Dcalcd = 1.193 Mg/m3, μ(Cu Kα) = 1.425 mm−1, crystal size 0.05 × 0.03 × 0.02 mm3, F(000) = 578, 11 099 reflections collected, 5139 independent reflections (Rint = 0.0674), R1 = 0.0604 [I > 2σ(I)], wR2 = 0.1535 [I > 2σ(I)], R1 = 0.0753 (all data), wR2 = 0.1706 (all data), goodness of fit = 1.051, Flack parameter = 0.03(3). The crystal structure was solved by direct methods (Olex 2) and refined by fullmatrix least-squares calculations on F2. Crystallographic data of 12 have been deposited at the Cambridge Crystallographic Data Centre as CCDC-1558287. PTP1B Inhibitory Activity Assay. As described previously.3,5,7a Cytotoxicity Assay. Cytotoxicity was assessed using the watersoluble tetrazolium MTS assay.35 Briefly, the human hepatoma L02 cells were seeded into 96-well plates and cultured overnight. Cells were treated with each test compound at varying concentrations. After incubation for 24 h, medium containing MTS solution was added and co-incubated at 37 °C for 2 h. Optical density was then acquired at 490 nm (reference 690 nm) on a microplate reader (SpectraMAX 340, Molecular Devices, CA, USA).

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(5) Wang, L.-J.; Xiong, J.; Zou, Y.; Mei, Q.-B.; Wang, W.-X.; Hu, J.-F. Phytochem. Lett. 2016, 18, 202−207. (6) (a) Wang, L.-J.; Xiong, J.; Liu, S.-T.; Pan, L.-L.; Yang, G.-X.; Hu, J.-F. J. Nat. Prod. 2015, 78, 1635−1646. (b) Wang, L.-J.; Xiong, J.; Lau, C.; Hu, J.-F. J. Asian Nat. Prod. Res. 2015, 17, 1220−1230. (c) Wang, L.-J.; Lau, C.; Xiong, J.; Hu, J.-F. Youji Huaxue 2016, 36, 1677−1680. (7) (a) Xiong, J.; Hong, Z.-L.; Gao, L.-X.; Shen, J.; Liu, S.-T.; Yang, G.-X.; Li, J.; Zeng, H.-Q.; Hu, J.-F. J. Org. Chem. 2015, 80, 11080− 11085. (b) Xiong, J.; Hong, Z.-L.; Xu, P.; Zou, Y.; Yu, S.-B.; Yang, G.X.; Hu, J.-F. Org. Biomol. Chem. 2016, 14, 4678−4689. (8) Wu, X.-Y.; Xiong, J.; Liu, X.-H.; Hu, J.-F. Chem. Biodiversity 2016, 13, 1030−1037. (9) (a) Johnson, T. O.; Ermolieff, J.; Jirousek, M. R. Nat. Rev. Drug Discovery 2002, 1, 696−709. (b) Panzhinskiy, E.; Ren, J.; Nair, S. Curr. Med. Chem. 2013, 20, 2609−2625. (10) Editorial Committee of the Flora of China, Chinese Academy of Sciences. In Flora of China; Zhang, H.-D., Ed.; Science Press: Beijing, 1998; Vol. 49 (3), pp 3−18. (11) Jiangsu New Medical College. A Dictionary of the Traditional Chinese Medicine; Shanghai Science and Technology Press: Shanghai, 1986; pp 191, 1601−1604, 1886, 2419. (12) (a) Zhao, P.; Gao, D.-F.; Xu, M.; Shi, Z.-G.; Wang, D.; Yang, C.R.; Zhang, Y.-J. Chem. Biodiversity 2011, 8, 1931−1942. (b) Ashihara, H.; Deng, W.-W.; Mullen, W.; Crozier, A. Phytochemistry 2010, 71, 559−566. (c) Wang, W.; Zhang, L.; Wang, S.; Shi, S.; Jiang, Y.; Li, N.; Tu, P. Food Chem. 2014, 152, 539−545. (13) Fu, L.-G., Jin, J.-M. China Plant Red Data Book. Rare and Endangered Plants I; Science Press: Beijing, 1992; pp 656−657. (14) World Conservation Monitoring Centre. Camellia crapnelliana. The IUCN Red List of Threatened Species 1998: e.T30407A9545190. http://www.iucnredlist.org/details/30407/0. (15) Furuya, T.; Orihara, Y.; Tsuda, Y. Phytochemistry 1990, 29, 2539−2543. (16) Khong, P. W.; Lewis, K. G. Aust. J. Chem. 1976, 29, 1351−1364. (17) Higuchi, R.; Komori, T.; Kawasaki, T.; Lassak, E. V. Phytochemistry 1983, 22, 1235−1237. (18) Cherry, R. F.; Khong, P. W.; Lewis, K. G. Aust. J. Chem. 1977, 30, 1397−1400. (19) Huang, Y.-L.; Nagai, S.; Tanaka, T.; Matsuo, Y.; Saito, Y.; Kouno, I. Molecules 2013, 18, 4868−4875. (20) Lee, S.; Kim, K. S.; Shim, S. H.; Park, Y. M.; Kim, B.-K. Arch. Pharmacal Res. 2003, 26, 902−905. (21) Knight, S. A. Org. Magn. Reson. 1974, 6, 603−611. (22) Reynolds, W. F.; Mclean, S.; Poplawski, J. Tetrahedron 1986, 42, 3419−3428. (23) Hui, W.-H.; Li, M.-M. Phytochemistry 1977, 16, 111−112. (24) Yuruker, A.; Orjala, J.; Sticher, O.; Rali, T. Phytochemistry 1998, 48, 863−866. (25) Olugbade, T. A.; Ogundaini, A.; Birlirakis, N.; Païs, M.; Martin, M. T. J. Nat. Prod. 2000, 63, 716−719. (26) Kutrzeba, L. M.; Li, X.-C.; Ding, Y.; Ferreira, D.; Zjawiony, J. K. J. Nat. Prod. 2010, 73, 707−708. (27) Barua, A. K.; Chakrabarti, P.; Pal, S. K.; Das, B. J. Indian Chem. Soc. 1970, 47, 195−198. (28) El-Gohary, H. M. A. Bull. Fac. Pharm. Cairo Univ. 2004, 42, 95− 104. (29) Flack, H. D. Acta Crystallogr., Sect. A: Found. Crystallogr. 1983, 39, 876−881. (30) Moffitt, W.; Woodward, R. B.; Moscowitz, A.; Klyne, W.; Djerassi, C. J. Am. Chem. Soc. 1961, 83, 4013−4018. (31) Jeong, S.-Y.; Nguyen, P.-H.; Zhao, B.-T.; Ali, M. Y.; Choi, J.-S.; Min, B.-S.; Woo, M.-H. Phytother. Res. 2015, 29, 1540−1548. (32) Yosioka, I.; Nishimura, T.; Matsuda, A.; Imai, K.; Kitagawa, I. Tetrahedron Lett. 1967, 8, 637−641. (33) Wang, S.-L.; Chen, Z.; Tong, X.-J.; Liu, Y.-L.; Lia, X.; Xu, Q.-M.; Li, X.-R.; Yang, S.-L. Helv. Chim. Acta 2013, 96, 1126−1133. (34) (a) Alqahtani, A.; Hamid, K.; Kam, A.; Wong, K. H.; Abdelhak, Z.; Razmovski-Naumovski, V.; Chan, K.; Li, K. M.; Groundwater, P. W.; Li, G. Q. Curr. Med. Chem. 2013, 20, 908−931. (b) Xu, J.-Q.;

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.jnatprod.7b00241. The HRESIMS and NMR spectra of compounds 1−7 and 12, NMR and mass data of the known compounds, and single-crystal X-ray data of compound 12 (PDF) Crystallographic data (CIF)

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AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected] (J. Ding). *E-mail: [email protected] (J.-F. Hu). ORCID

Jin-Feng Hu: 0000-0002-0367-1454 Author Contributions #

J. Xiong and J. Wan contributed equally to this work.

Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was financially supported by NSFC grants (Nos. 81202420, 21472021). The authors are grateful to Mr. X.-C. Hu (Director, Foshan Municipal Forestry Research Institute, Guangdong, PR China) for providing the plant material.

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REFERENCES

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Camellianols AâG, Barrigenol-like Triterpenoids with PTP1B Inhibitory

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