Chromones and tannins from the fruit of Euscaphis japonica var. wupingensis

Abstract

Euscaphis japonica var. wupingensis is a variety of E. japonica in the family Staphyleaceae. The biological characteristics of E. japonica var. wupingensis have been well described, but few studies have been conducted on its constituents. After repeated separation using column chromatography and preparative high performance liquid chromatography (HPLC), ten compounds were isolated from the methanol extract of fruit of E. japonica var. wupingensis. The structure of the components was characterized on the basis of spectroscopic data, including nuclear magnetic resonance (NMR), and mass spectra (MS). These compounds included five chromone derivatives: isobiflorin (1), biflorin (2), 2-methyl-5,7-dihydroxy-chromone-7-O-ß-D-glucopyranoside (5), 5,7-dihydroxy-2-methyl-4H-chromen-4-one (6), and quercetin-3-O-D-arabinoside (7), and four tannins: eugeniin (3), ellagic acid (8), 3, 3′-di-O-methylellagic acid 4-(5”-acetyl) -α-L-arabinofuranoside (9), 3,3′-di-O-methylellagic acid (10), and methyl 3,4,5-trihydroxybenzoate (4). The antioxidant activity of the isolated compounds were tested. Ellagic acid (8) exhibited potent 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity with an SC50 value of 4.05 M.

Full Article

Chromones and Tannins from the Fruit of Euscaphis japonica var. wupingensis

Shunzhi Liu,^a,b Tao Zhu,^a,c Yingkun Qiu,^d Wenyu Qi,^a Hui Wu,^a Bangping Cai,^a,b,* and Jinguo Lin ^a,*

Euscaphis japonica var. wupingensis is a variety of E. japonica in the family Staphyleaceae. The biological characteristics of E. japonica var. wupingensis have been well described, but few studies have been conducted on its constituents. After repeated separation using column chromatography and preparative high performance liquid chromatography (HPLC), ten compounds were isolated from the methanol extract of fruit of E. japonica var. wupingensis. The structure of the components was characterized on the basis of spectroscopic data, including nuclear magnetic resonance (NMR), and mass spectra (MS). These compounds included five chromone derivatives: isobiflorin (1), biflorin (2), 2-methyl-5,7-dihydroxy-chromone-7-O-ß-D-glucopyranoside (5), 5,7-dihydroxy-2-methyl-4H-chromen-4-one (6), and quercetin-3-O-D-arabinoside (7), and four tannins: eugeniin (3), ellagic acid (8), 3, 3′-di-O-methylellagic acid 4-(5”-acetyl) -α-L-arabinofuranoside (9), 3,3′-di-O-methylellagic acid (10), and methyl 3,4,5-trihydroxybenzoate (4). The antioxidant activity of the isolated compounds were tested. Ellagic acid (8) exhibited potent 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity with an SC₅₀ value of 4.05 M.

Keywords: Euscaphis japonica var. wupingensis; Tannins; Chromones; DPPH scavenging activity

Contact information: a: College of Material Engineering, Fujian Agriculture and Forestry University, Fuzhou, Fujian 35002, China; b: Xiamen Botanical Garden, Xiamen, Fujian 361003, China; c: Furniture Products Quality Supervision and Testing Center of Putian, Xianyou, Fujian 351256, China; d: Fujian Provincial Key Laboratory of Innovative Drug Target Research, School of Pharmaceutical Sciences, Xiamen University, South Xiang-An Road, Xiamen 361102, China;

* Corresponding authors:cbangping@163.com; fjlingjg@126.com

INTRODUCTION

Euscaphis japonica var. wupingensis (Cai et al. 2018) is a variety in the bladdernut family Staphyleaceae. It is a deciduous shrub or small tree, glabrous, with leaves opposite, 5-7-pinnate, and it is generally found in the forests and mountains of Fujian, China. Its pericarp is yellow, and it can be distinguished easily from E. japonica.

E. japonica is a traditional Chinese medicinal material (Luo et al. 2012). Its roots, root bark, fruit, and flowers can be used as medicines because of a variety of effects (Li et al. 2016, 2018), and the pesticide effects are very different in the plant (Dong et al. 2004; Lee et al. 2009; Zhang et al. 2012). The fruits have the effect of treating headache, dizziness, and cold. The study of plant secondary metabolites is a crucial step in the scientific and rational use of plants (Yu et al. 2017). At present, 84 kinds of compounds have been isolated from EuscaphisSieb. et Zucc., and the main active substances are triterpenoids, flavonoids, and phenolic acids (Tekeda et al. 2000; Hajime et al. 2009; Huang et al. 2014; Liang et al. 2018).

As a new variety, studies up to this point on E. japonica var. wupingensis have focused mainly on the morphological and biological characteristics, while its chemical properties have not been reported yet. In this paper, the chemical constituents from the fruits of this new variety were studied, which provides a theoretical basis for its rational utilization and functional development.

EXPERIMENTAL

Materials

Fruits of E. japonica var. wupingensis were collected from Huangtu hill (Wuping country, Fujian province, China) in October 2017. This site is located at 25°11’30″ N, 116°02’37″ E, altitude 400 to 520 m. The samples were oven-dried at 80 °C for 24 h and crushed before extraction.

The analytically pure solvents used in the extract and open-column separation process, including ethanol, methanol, and acetonitrile, were purchased from China National Pharmaceutical Corporation, Limited. The HPLC grade acetonitrile and methanol were obtained from Tedia (Fairfield, CT, USA). Ascorbic acid (Vc) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) were purchased from J&K Scientific Co. Ltd. (Beijing, China).

General Equipment

The ¹H and ¹³C nuclear magnetic resonance (NMR) spectra were taken using TMS as the internal standard on a Bruker Avance III 600 FT NMR spectrometer (Bruker Corporation, Billerica, MA, USA). Chemical shifts were recorded as δ (ppm) values with dimethyl sulfoxide-deuterium (Sigma-Aldrich, St. Louis, MO, USA) as the solvent. Coupling constants (J) were recorded in Hz, and multiplicities were abbreviated as follows: s = singlet, d = doublet, t = triplet, br = broad, and m = multiplet.

The ESI-MS analysis was detected on a Thermo Q-Exactive Orbitrap Mass spectrometer (Thermo Fisher Scientific Corporation, Waltham, MA, USA), which was equipped with electrospray ionization source (ESI).

Column chromatography was performed on a Cosmosil 75 C18-OPN Column (75 μm, Nakalai Tesque Co. Ltd., Kyoto, Japan). The preparative HPLC was performed with a Varian binary gradient LC system (Varian Inc. Corporate, Santa Clara, CA, USA) containing two solvent deliver modules (PrepStar 218), a photodiode array detector (ProStar 335), using an the preparative Cosmosil ODS column (250 mm × 20.0 mm i.d., 5 m, Cosmosil, Nakalai Tesque Co. Ltd., Kyoto, Japan). A Sephadex LH-20 column (GE Healthcare, Sweden) was used for column chromatography with a glass column (120 cm × 1.5 cm inner diameter); methanol was used as the eluent.

Extraction and Isolation

The fruits (100 g) were ultrasonically extracted with methanol for one hour (×3) under room temperature and evaporated until dry before weighing. The methanol extraction yielded 5.8 g of solid material having a brown color. For separation, 5.0 g of extract was chromatographed into a reversed-phase column, resulting in 5 fractions (abbreviated Fr. 1 – Fr. 5) with eluent of CH₃OH-water (20:80, 40:60, 60:40, 80:20, 100, v/v). Fr. 2 (2.5 g) was subjected to ODS column (25 g) and gradiently eluted with acetonitrile/H₂O (10% to 25%, 2L) to give 12 subfractions Fr. 2-1 – Fr. 2-12. Compound 1 was isolated from Fr. 2-6 (500 mg), through a preparative reversed-phase HPLC column, and gradient-eluted with CH₃OH-water from 10:90 to 50:50 (v/v) at a flow of 8 mL/min. Fr. 3 (120 mg) was subjected to a Sephadex LH-20 column and eluted with methanol to afford compounds 6 and 7. Further separation on Fr. 2-7 (800 mg), Fr. 2-9 (300 mg), and Fr. 2-12 (400 mg) by preparative HPLC resulted in the isolation of compounds 2, 3, and 5, respectively. A preparative reversed-phase HPLC isocratic gradient eluted with CH₃OH-H₂O (0 – 60 min; 5% – 100 % CH₃OH, v/v) at a flow of 8 mL/min was used to isolate compounds 8, 9, and 10 from Fr. 4. The isolation scheme of these compounds is shown in Fig. 1.

Fig. 1. Diagram of the extract and isolation of E. japonica var. wupingensis

DPPH Radical Scavenging Activity

The compound solutions of 50, 25, 12.5, 6.25, and 3.125 μM were prepared with anhydrous ethanol, using vitamin C (Vc) as a positive control. DPPH radical scavenging activities of the isolated compounds were investigated according to the reported literature (Qiu et al. 2002). Briefly, a solution of the test compound in EtOH (0.1 mL), and 80 mM DPPH radical in EtOH (0.1 mL) was incubated at room temperature for 30 min. Reduction of the DPPH radical was measured at 517 nm. Measurements were performed in duplicate, and the concentration required for a 50% reduction (50% scavenging concentration, SC₅₀) of 40 mM DPPH radical was determined graphically, as shown in Table 2.

Isobiflorin, C₁₆H₁₈O₉ (1)

Compound 1 was obtained as colorless needles. ESI-MS: m/z 353 [M-H]^–. The ¹H-NMR (DMSO-d₆, 600 MHz): δ_H 13.03 (1H, br.s, 5-OH), 6.25 (1H, s, H-6), 6.20 (1H, s, H-3), 4.63 (1H, d, J = 9.5 Hz, H-1’), 2.35 (3H, s, 2-CH₃); The ¹³C-NMR (DMSO-d₆, 151 MHz) spectral data are listed in Table 1.

Biflorin, C₁₆H₁₈O₉ (2)

Compound 2 was isolated as colorless needles. ESI-MS: m/z 353 [M-H]^–. ¹H-NMR (DMSO-d₆, 600 MHz): δ_H 13.40 (1H, s, 5-OH), 6.39 (1H, s, H-8), 6.17 (1H, s, H-3), 4.56 (1H, d, J = 9.7 Hz, H-1’), 2.35 (3H, s, 2-CH₃); The ¹³C-NMR (DMSO-d₆, 151 MHz) spectral data are shown in Table 1.

Eugeniin, C₄₁H₃₀O₂₆ (3)

Compound 3 was obtained as a puce amorphous powder. ESI-MS: m/z 939 [M+H]⁺. ¹H-NMR (DMSO-d₆, 600 MHz): δ_H 6.88 (2H, s, galloyl-H), 6.87 (2H, s, galloyl-H), 6.81 (2H, s, galloyl-H), 6.76 (1H, s, HHDP-H), 6.28 (1H, s, HHDP-H), 5.68 (1H, t, J = 9.9 Hz, H-1), 5.53 (1H, t, J = 9.7 Hz, H-3), 5.37 (1H, br. d, J = 8.5 Hz, H-2), 5.12 (1H, dt, J = 14.3, 7.0 Hz, H-6), 4.55 (1H, br. dd, J = 9.9, 7.2 Hz, H-5), 3.83 (1H, br. d, J = 13.0 Hz, H-6). The ¹³C-NMR (DMSO-d₆, 151 MHz) spectral data were summarized as follows: δ 168.1 (C-7’’’’), 168.1 (C-7’’’’’), 167.4 (C-7’), 165.9 (C-7’’), 165.7 (C-7’’’), 146.1 (C-3, 5’), 146.0 (C-3’’, 5’’), 145.9 (C-3’’’, 5’’’), 145.7 (C-4’’’’, 6’’’’), 145.7 (C-4’’’’’, 6’’’’’), 139.4 (C-4’), 139.2 (C-4’’), 139.2 (C-4’’’), 135.9 (C-5’’’’), 135.7 (C-5’’’’’), 124.8 (C-2’’’’), 124.2 (C-2’’’’’), 119.2 (C-1’), 118.9 (C-1’’), 118.8 (C-1’’’), 115.8 (C-3’’’’), 115.7 (C-3’’’’’), 109.3 (C-2’, 2’’, 2’’’), 109.2 (C-6’, 6’’, 6’’’), 106.2 (C-1’’’’), 105.8 (C-1’’’’’), 98.8 (C-1), 73.5 (C-3), 72.7 (C-5), 72.1 (C-2), 70.6 (C-4), 63.0 (C-6).

Methyl 3,4,5-trihydroxybenzoate , C₈H₈O₅ (4)

Compound 4 was obtained as a colorless needles. ESI-MS: m/z 185 [M+H]⁺. ¹H-NMR (DMSO-d₆, 600 MHz): δ_H 6.94 (2H, s, H-2, 6), 3.74 (3H, s, CH₃). ¹³C-NMR (DMSO-d₆, 151 MHz): δ_C 166.8 (CO), 146.0 (C-3, 5), 138.9 (C-4), 119.7 (C-1), 108.9 (C-2, 6), 52.1 (CH₃).

2-Methyl-5,7-dihydroxy-chromone-7-O-ß-D-glucopyranoside, C₁₆H₁₈O₉ (5)

Compound 5 was a light yellow powder. ESI-MS: m/z 355 [M+H]⁺, 353[M-H]^–. ¹H-NMR (DMSO-d₆, 600 MHz): δ_H 12.83 (1H, br s, 5-OH), 6.66 (1H, d, J = 2.0 Hz, H-8), 6.42 (1H, d, J = 2.2 Hz, H-6), 6.26 (1H, s, H-3), 5.04 (1H, d, J = 7.5 Hz, H-1’), 2.39 (3H, s, 2-CH₃); The ¹³C-NMR (DMSO-d₆, 151 MHz) spectral data are shown in Table 1.

5,7-Dihydroxy-2-methyl-4H-chromen-4-one, C₁₀H₈O₄ (6)

Compound 6 was a light yellow crystal. ESI-MS: m/z 193[M+H]⁺. ¹H-NMR (DMSO-d₆, 600 MHz): δ_H 6.33 (1H, d, J = 2.0 Hz, H-3), 6.17 (2H, s, H-6, 8), 2.35 (3H, s, 2-CH₃). The ¹³C-NMR (DMSO-d₆, 151 MHz) spectral data are shown in Table 1.

Quercetin-3-O-ß-D-arabinoside, C₂₀H₁₈O₁₁ (7)

Compound 7 was a yellow powder. ESI-MS: m/z 435 [M+H]⁺. ¹H-NMR (DMSO-d₆, 600 MHz): δ_H 12.63 (1H, s, 5-OH), 7.65 (1H, dd, J = 2.0, 8.4Hz, H-6’), 7.53 (1H, d, J = 2.2 Hz, H-2’), 6.85 (1H, d, J = 8.4 Hz, H-5’), 6.39 (1H, d, J = 2.0 Hz, H-8), 6.21 (1H, d, J = 2.0 Hz, H-6), 5.26 (1H, d, J = 5.3 Hz, H-1”); ¹³C-NMR (DMSO-d₆, 151 MHz): δ_C 177.9 (C-4), 164.9 (C-7), 161.6 (C-5), 156.7 (C-2), 156.7 (C-9), 149.1 (C-4’), 145.5 (C-3’, 5’), 134.1 (C-3), 122.4 (C-2’, 6’), 121.3 (C-1’), 116.2 (C-3’, 5’), 115.9 (C-2’, 6’), 104.3 (C-10), 101.9 (C-1’’), 99.2 (C-6), 94.0 (C-8), 72.1 (C-3’’), 71.2 (C-2’’), 66.6 (C-4’’), 64.8 (C-5’’).

Ellagic acid, C₁₄H₆O₈ (8)

Compound 8 was a grey powder. ESI-MS: m/z 301 [M+H]⁺. ¹H-NMR (DMSO-d₆, 600 MHz): δ_H 7.45 (2H, s, H-5,5′); ¹³C-NMR (DMSO-d₆, 151 MHz): δ_C 159.9 (C-7,7′), 148.9 (C-4,4′), 136.8 (C-3,3′), 130.1 (C-2,2′), 113.1 (C-6,6′), 110.1 (C-5,5′), 106.7 (C-1,1′).

3,3′-Di-O-methylellagic acid 4-(5”-acetyl)-a-L-arabinofuranoside, C₂₃H₂₀O₁₃ (9)

Compound 9 was obtained as white amorphous powder. ESI-MS: m/z 503 [M-H]^–. ¹H-NMR (DMSO-d₆, 600 MHz): δ_H 7.73 (1H, s, H-5), 7.52 (1H, s, H-5’), 5.68 (1H, d, H-1’’), 4.08 (3H, s, 3-OCH₃), 4.05 (3H, s, 3’-OCH₃), 3.87 (1H, dd, J=6 and 4 Hz, H-3’’), 2.04 (3H, s, 6’’-CH₃); ¹³C-NMR (DMSO-d₆, 151 MHz): δ_C 170.7 (C-6’’), 159.1 (C-7), 142.5 (C-3, 2), 142.2 (C-3’, 2’), 113.3 (C-5, 5’), 112.4 (C-6, 6’), 108.0 (C-1’’), 83.1 (C-4’’), 82.2 (C-2’’), 77.4 (C-3’’), 64.1 (C-5’’), 62.0 (3-OCH₃), 61.3 (3’-OCH₃), 21.1 (6’’-CH₃)。

3,3′-Di-O-methylellagic acid ,C₁₆H₁₀O₈ (10)

Compound 10 was obtained as yellow powder. ESI-MS: m/z 329 [M-H]^–. ¹H-NMR (DMSO-d₆, 600 MHz): δ_H 7.51 (2H, s, H-5, 5’), 4.04 (6H, s, 3, 3’-OCH₃); ¹³C-NMR (DMSO-d₆, 151 MHz): δ_C 159.0 (C-7,7′), 152.9 (C-4,4′), 140.8 (C-3,3′), 141.7 (C-2,2′), 112.6 (C-6, 6′), 112.0 (C-5, 5′, 1, 1′), 61.4 (3,3’-OCH₃).

Fig. 2. Chromones and tannins from the fruit of Euscaphis japonica var. wupingensis

Table 1. ¹³C-NMR (DMSO-d₆, 151 MHz) data of compounds 1, 2, 5, and 6

RESULTS AND DISCUSSION

Phytochemistry of the Fruit of E. japonica var. wupingensis

Isolation of the fruit of E. japonica var. wupingensis yielded five chromones, four tannins, and methyl 3,4,5-trihydroxybenzoate. Their chemical structures were determined by their ESI-MS, ¹H-NMR, and ¹³C-NMR spectra. Two chromones, 2-methyl-5,7-dihydroxy-chromone-7-O-ß-D-glucopyranoside (5) and quercetin-3-O-ß-D-arabinoside (7), and two tannin, eugeniin (3) and 3,3′-di-O-methylellagic acid 4-(5”-acetyl)–L-arabinofuranoside (9), were isolated from the family of Staphyleaceae for the first time. The structures of the isolated compounds are shown in Fig. 2.

Compound 3 was isolated as a puce amorphous powder. The dark color, high polarity, as well as the high molecular weight, induced by the ESI-MS qusio-molecular ion peak at m/z 939 [M+H]⁺, indicated that compound 3 is a tannin derivate. By comparing it ¹³C-NMR data with those reported in literature (Lian et al. 2017), the structure of 3 was determined as eugeniin.

Compound 5 was obtained as a light yellow powder. In low field of ¹H-NMR (DMSO-d₆, 600 MHz) of 5, the signal of δ_H 12.83 (1H, br.s) belongs to the C-5 hydroxyl, forming intramolecular hydrogen bond with C=O. A pair of AM spin system aromatic proton signals were found at δ_H 6.66 (1H, d, J = 2.0 Hz) and 6.42 (1H, d, J = 2.2 Hz), belonging to the H-8 and H-6 of the chromone’s ring. The signal at δ_H 6.26 (1H, s) was assigned to H-3. The high field of ¹H-NMR shown the presence of methyl at δ_H 2.39 (3H, s, 2-CH₃). The ¹³C-NMR revealed an oxy-glycosylated glucose, based on the signals at δ_c 95.0 (C-1’), 77.6 (C-3’), 76.8 (C-5’), 73.5 (C-2’), 70.0 (C-4’) and 61.1 (C-6’). According to the presence of 5-OH and absence of 7-OH ¹H-NMR signal, the glucosyl was considered to be attached to C-7. Thus, compound 5 was 2-mehyl-5,7-dihydroxychromanone glucoside. The above data is consistent with the reported NMR data (Yang et al. 2006). Therefore, the compound was identified as 5,7-dihydroxy-2-methylchromanone-7-O-β-D-glucoside.

Compound 7 was isolated as yellow powder. Both the hydrochloric acid-magnesium powder (HCl-Mg) reaction and the Molish reaction were positive, indicating that the 7 is a flavonoid glycoside. In the ¹H-NMR spectrum, the signal of 5-OH was shown at δ_H 12.63 (1H, s, 5-OH). The AMX spin system signals at δ_H 7.65 (1H, d, J = 2.0 Hz), 7.64 (1H, d, J = 2.2 Hz), 7.53 (1H, d, J = 2.2 Hz) suggests the 3’,4’-disubstituted B flavonoid ring; The meta-coupled benzene ring signals at δ_H 6.39 (1H, d, J = 2.0 Hz) and 6.21 (1H, d, J = 2.0 Hz) belonged to H-8 and H-6 in the A ring, respectively. The signal at δ_H 5.26 (1H, d, J = 5.3 Hz, H-1”) was attributed to a terminal proton of the sugar. By comparing the ¹³C-NMR data with those in the literature (Jiang et al. 2009), compound 7 was identified as quercetin 3-O-α-L-arabinopyranoside.

Compound 9 was obtained as white amorphous powder. The ¹H-NMR spectrum showed 9 proton signals, including two benzene ring signals at δ_H 7.73, 7.52; two methoxy signals at δ_H4.08, 4.05; an acetyl signal at δ_H 2.04, and a set of glycoside proton signal ranging from δ_H 5.68 to 3.87. The ¹³C-NMR shows the unsaturated lactone signal at δ 159.1; an arabinofuranose signal δc 108.1, 83.1, 82.2, 77.4, and 64.1. ¹H-NMR and ¹³C-NMR indicate that the compound is a steroidal compound linked to a glycoside; the ¹³C-NMR signals at δ_C 62.0 and δ 61.3 suggest methoxy groups. The NMR data were similar to the reported results (Tanaka et al. 2001) (Jules et al. 2007). Therefore, compound 9 is identified as 3,3′-di-O-methylellagic acid 4-(5”-acetyl)-α-L-arabinofuranoside.

By comparing NMR data with those reported in literature, other known compounds were identified as: isobiflorin (1) (Takashi et al. 1993) (Lee et al. 2016), biflorin (2) (Li et al. 2009) , methyl 3,4,5-trihydroxybenzoate (4) (Yang et al. 1998), 5, 7-dihydroxy-2-methyl-4H-chromen-4-one (6) (Cao et al. 2005), ellagic acid (8) (Xiao et al. 2017), and 3,3′-di-O-methylellagic acid (10) (Nono, et al. 2014).

Antioxidant Activity

Table 2 shows that the chromones and quinones in the extract of E. japonica var. wupingensis have a good scavenging effect on DPPH free radicals. Higher concentrations resulted in a stronger ability to scavenge free radicals. Ellagic acid (8, SC₅₀ of 4.05 μM) has the strongest effect on scavenging DPPH freeness, which is twice as high as that of vitamin C (SC₅₀ of 9.85 μM).

Table 2. Antioxidant Activity of Compounds Isolated from E. japonica var. wupingensis

CONCLUSIONS

1. E. japonica var. wupingensis was extracted with methanol, and the extract components were isolated using column chromatography. Five chromones, four tannins, and methyl 3,4,5-trihydroxybenzoate were identified as isobiflorin (1), biflorin (2), 2-methyl-5,7-dihydroxy-chromone-7-O–D-glucopyranoside (5), 5,7-dihydroxy-2-methyl-4H-chromen-4-one (6), quercetin-3-O-D-arabinoside (7), eugeniin (3), ellagic acid (8)_, 3,3′-di-O-methylellagic acid 4-(5”-acetyl)–L-arabinofuranoside (9), and 3,3′-di-O-methylellagic acid (10).
2. For the first time, the chemical composition isolated from the Euscaphis japonica var. wupingensis is reported. Two chromones (5 and 7) and two tannins (3 and 9) were first isolated from the genus of Euscaphis.
3. Ellagic acid (8) has stronger antioxidant activity than vitamin C, and the specific efficacy needs to be further studied.

ACKNOWLEDGMENTS

The authors are grateful for the funding from Fujian Provincial Department of Finance Research Fund “Research and Extension of Key Technique on Characteristic and Identification of Import Wood” (No. K8115004A) and Fujian Provincial Science and Technology Bureau Fund “Germplasm collection and space mutation breeding of medicinal and ornamental plants of Euscaphis japonica” (No. 3502Z20144073).

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Article submitted: January 25, 2019; Peer review completed: March 23, 2019; Revised version received: April 2, 2019; Accepted: May 16, 2019; Published: May 22, 2019.

DOI: 10.15376/biores.14.3.5355-5364