Chemical Structures of Phenylbutanoids From Rhizomes of Zingiber cassumunar

Abstract

Zingiber cassumunar is widely distributed in Asia, and its rhizomes are used for asthma treatment in traditional medicine and as a spice. Five new phenylbutanoids, cassumunols I–M (1-5), were isolated from Z cassumunar rhizomes collected in Thailand, and their structures were characterized on the basis of physiochemical and chemical evidence.

Keywords

phenylbutanoid cassumunol Zingiberaceae medicinal food

Zingiber cassumunar Roxb. (Family Zingiberaceae) is widely distributed in Southeast Asia, and its rhizomes are used for the treatment of asthma, bronchitis, and gastrointestinal distress in traditional medicine and as a spice in Thailand.^1-4 We have reported the isolation and structure elucidation of various phenylbutanoids, including phlains I–VI and cassumunols A–H, from the methanolic (MeOH) extract of Z cassumunar rhizomes.^5,6 Those constituents showed biofunctional effects, such as nitric oxide production inhibitory effects induced by lipopolysaccharide in mouse peritoneal macrophages and inhibitory effects on the invasion of human fibrosarcoma HT 1080 cells. In the course of our studies on the bioactive constituents from medicinal foods^7-11 and Z cassumunar, we have isolated 5 new phenylbutanoids, cassumunols I–M (1-5), from the rhizomes of Z cassumunar. In the present study, we describe the isolation and structure elucidation of these new constituents.

The MeOH extract of the rhizomes of Z cassumunar was partitioned in an EtOAc-H₂O (1:1, v/v) mixture to give EtOAc-soluble and H₂O-soluble phases, as reported previously.^5,6 The EtOAc-soluble fraction was subjected initially to normal- and reversed-phase column chromatography (CC) and finally to HPLC to give cassumunols I (1, 0.011% from the dried rhizomes), J (2, 0.0013%), K (3, 0.00061%), L (4, 0.0031%), and M (5, 0.0028%) (Figure 1).

Figure 1.

Constituents from rhizomes of Z cassumunar.

Cassumunol I (1) was isolated as a pale-yellow oil with positive optical rotation ([α]²⁵_D + 12.4 in CHCl₃). The IR spectrum of 1 showed absorption bands assignable to a hydroxy group and an olefin moiety (3450 and 1655 cm^–1), and its UV spectrum had an absorption maximum assignable to a phenyl moiety (281 nm). In the EIMS of 1, the molecular ion peak was observed at m/z 208 (M⁺) and the molecular formula C₁₂H₁₆O₃ was determined by high-resolution (HR) EIMS measurement. The ¹H NMR and ¹³C NMR spectra (in CDCl₃, ¹³C: see Table 1) of 1, which were assigned on the basis of various NMR experiments, showed signals for 2 methoxy groups [δ3.87, 3.88 (3H each, both s, CH₃O-3′, 4′, interchangeable)], a methine bearing an oxygen function [δ4.32 (1H, m, H-2)], 3 olefinic protons [δ5.14 (1H, dd, J = 1.4, 10.5 Hz, H-4a), 5.27 (1H, dd, J = 1.4, 17.0 Hz, H-4b), 5.94 (1H, ddd, J = 5.7, 10.5, 17.0 Hz, H-3)], and a trisubstituted benzene ring [δ6.76 (1H, d-like, J = 8.9 Hz, H-6′), 6.78 (1H, s-like, H-2′), 6.83 (1H, d, J = 8.9 Hz, H-5′)] (please see Supplemental file).

Table 1.

¹³C NMR Spectroscopic Data of Cassumunols I–M (1-5) (Measured in CDCl₃).

Position	1	2	3	4	5
1	43.5	77.5	65.8	70.8	77.1
2	73.7	77.1	83.7	58.4	58.2
3	140.3	136.6	123.9	55.1	55.6
4	115.1	117.1	128.9	61.3	61.3
2-OMe			56.7		57.2
1′	130.3	132.9	117.0	132.0	117.6
2′	112.8	110.1	151.7	109.7	151.5
3′	149.1	149.1	97.7	149.3	97.5
4′	148.0	149.2	150.0	149.4	149.5
5′	111.4	111.1	143.5	111.4	143.8
6′	121.6	119.6	109.9	119.0	110.9
2′-OMe			56.7		56.5
3′-OMe	55.9¹	56.0^b		56.1^a
4′-OMe	56.0¹	56.0^b	56.2	56.0^a	56.7
5′-OMe			56.6		56.3

Interchangeable.

Overlap.

As shown in Figure 2, DQF-COSY experiments on 1 indicated the presence of partial structures represented by bold lines, and HMBC experiments revealed long-range correlations between the following protons and carbons: H-1 and C-2, 3, 2′, 6′; H-3 and C-1, 2; H-4 and C-2, 3; H-2′ and C-1, 4′; H-5′ and C-3′; and OCH₃ × 2 and C-3′; 4′. On the basis of these findings, the planar structure of 1 was characterized to be 1-(3,4-dimethoxyphenyl)but-3-en-2-ol. Finally, the absolute configuration at the 2-position was characterized by means of a modified Mosher's method.¹² Treatment of 1 with (–)-α-methoxy-α-(trifluoromethyl)phenylacetyl chloride [(–)-MTPA-Cl] in pyridine yielded (S)-MTPA ester (1a). On the other hand, (R)-MTPA ester (1b) was derived from 1 by treatment with ( + )-MTPA-Cl in pyridine. As shown in Figure 2, signals due to protons at 1-, 2′-, 5′-, and 6′-positions and CH₃O-3′ and −4′ in 1a were observed at higher fields than those of 1b [Δδ: negative], whereas the signals due to protons at 3- and 4-positions in (S)-MTPA ester (1a) were observed at lower fields than those of (R)-MTPA ester (1b) [Δδ: positive]. Thus, the absolute configuration at 2-position in 1 was determined to be S. The structure of cassumunol I (1) was determined to be (S)-1-(3,4-dimethoxyphenyl)but-3-en-2-ol.

Figure 2.

Important 2D NMR correlations and determination of absolute configuration at 2-position of 1.

Cassumunol J (2) was obtained as a pale-yellow oil. Its IR spectrum indicated the presence of hydroxy groups and an olefin moiety, and its UV spectrum showed an absorption maximum that suggested a phenyl moiety. The molecular formula of 2 was determined by HRCIMS measurement of the molecular ion peak. The ¹H NMR and ¹³C NMR spectra (in CDCl₃, ¹³C: see Table 1) of 2 showed signals due to 2 methoxy groups [δ3.88, 3.89 (3H each, all s, CH₃O-3′, 4′, interchangeable)], 3 olefinic protons [δ5.17 (1H, d-like, J = 11.0 Hz, H-4a), 5.28 (1H, d-like, J = 17.1 Hz, H-4b), 5.74 (1H, ddd, J = 5.5, 11.0, 17.1 Hz, H-3)], 2 methines [δ4.23 (1H, dd-like J = 5.5, 5.5 Hz, H-2), 4.46 (1H, d, J = 5.5 Hz, H-1)] with an oxygen function, and a trisubstituted benzene ring [δ6.84 (1H, d, J = 8.6 Hz, H-5′), 6.89 (1H, dd, J = 1.8, 8.6 Hz, H-6′), 6.91 (1H, d-like, J = 1.8 Hz, H-2′)] (please see Supplemental file). On the basis of DQF-COSY and HMBC experiments (Figure 3), the structure of cassumunol J (2) was determined to be 1-(3,4-dimethoxyphenyl)but-3-ene-1,2-diol, although the absolute stereochemistry was not determined.

Figure 3.

Important 2D NMR correlations of 2-5.

Cassumunol K (3) was obtained as a pale-yellow oil. Its IR spectrum indicated the presence of a hydroxy group and an aromatic ring. The molecular formula of 3 was determined by HREIMS measurement of the molecular ion peak. The ¹H NMR and ¹³C NMR spectra (in CDCl₃, ¹³C: see Table 1) of 3 showed signals due to 4 methoxy groups, 2 olefinic protons [δ5.90 (1H, dd, J = 7.8, 15.9 Hz, H-3), 6.93 (1H, d, J = 15.9 Hz, H-4)], a methine with an oxygen function, and a tetrasubstituted benzene ring (please see Supplemental file). On the basis of DQF-COSY and HMBC experiments, the structure of cassumunol K (3) was determined to be (E)-2-methoxy-4-(2,4,5-trimethoxyphenyl)but-3-en-1-ol, although the absolute stereochemistry was not determined.

Cassumunols L (4) and M (5), both obtained as a pale-yellow oil, showed absorption bands due to hydroxy groups (4 and 5: 3450 cm^–1) and an epoxy moiety (4: 1262, 972, 841 cm^–1; 5: 1208, 972, 841 cm^–1) in their IR spectra. The molecular formulas of 4 and 5 were determined by HREIMS measurement of the molecular ion peak. The ¹H NMR and ¹³C NMR spectra (in CDCl₃, ¹³C: see Table 1) of 4 and 5 showed signals due to 2 or 4 methoxy groups [4: δ 3.88, 3.90 (3H each, both s, CH₃O-3′, 4′, interchangeable); 5: δ 3.34, 3.80, 3.86, 3.90 (3H each, all s, CH₃O-1, 2′, 4′, 5′)], a methylene [4: δ 3.66 (1H, dd, J = 4.3, 12.8 Hz, H-4a), 3.94 (1H, dd, J = 1.8, 12.8 Hz, H-4b); 5: δ 3.55 (1H, dd, J = 4.3, 12.9 Hz, H-4a), 3.88 (1H, m, H-4b)] with an oxygen function, 3 methines [4: δ 3.28 (1H, m, H-2), 3.41 (1H, m, H-3), 4.88 (1H, d, J = 3.1 Hz, H-1); 5: δ 3.19 (1H, dd, J = 2.4, 6.1 Hz, H-2), 3.24 (1H, dt-like, J = 2.4, 4.3 Hz, H-3), 4.48 (1H, d, J = 6.1 Hz, H-1)] with an oxygen function, and a tri- or tetrasubstituted benzene ring [4:δ6.87 (1H, d, J = 8.6 Hz, H-5′), 6.92 (1H, dd-like, J = 1.7, 8.6 Hz, H-6′), 6.93 (1H, d-like, J = 1.7 Hz, H-2′); 5: δ6.53, 6.96 (1H each, both s, H-3′, 6′)] (please see Supplemental file). In addition, the ¹³C NMR spectra [4:δ55.1 (C-3), 58.4 (C-2); 5:δ55.6 (C-3), 58.2 (C-2)] suggested that compounds 4 and 5 had an epoxy moiety.^13,14 On the basis of DQF-COSY and HMBC experiments, the structures of cassumunol L (4) and cassumunol M (5) were determined as shown, although their absolute stereochemistry was not determined.

In conclusion, 5 new phenylbutanoids, cassumunols I–M (1-5), were isolated from the rhizomes of Z cassumunar collected in Thailand. Further investigations of their biological effects are warranted.

Experimental

General

UV spectra, Shimadzu UV-1600 spectrometer; IR spectra, Shimadzu FTIR-8100 spectrometer; specific rotations, Horiba SEPA-300 digital polarimeter (l = 5 cm); CIMS, EIMS, HRCIMS, and HREIMS, JEOL JMS-GCMATE mass spectrometer; ¹H NMR spectra, JEOL JNM-LA 500 (500 MHz), and JEOL JNM-ECA 600 (600 MHz) spectrometers; ¹³C NMR spectra, JEOL JNM-LA 500 (126 MHz), and JEOL JNM-ECA 600 (151 MHz) spectrometers with tetramethylsilane as the internal standard; HPLC detector, Shimadzu RID-10A refractive index detector; and HPLC columns, YMC-Pack ODS-A (YMC, Inc., 250 × 4.6 mm i.d.) and (250 × 20 mm i.d.) columns for analytical and preparative purposes, respectively. The following materials were used for chromatography: normal-phase silica gel CC, Silica gel BW-200 (Fuji Silysia Chemical, Ltd, 150-350 mesh); reversed-phase silica gel CC, Chromatorex ODS DM1020T (Fuji Silysia Chemical, Ltd, 100-200 mesh).

Plant Material

Z cassumunar rhizomes were cultivated in Nakhon Si Thammarat, Thailand in 2007. The plant was identified by one of the authors (Y. P.). A specimen of the plant is stored in our laboratory.

Extraction and Isolation

A MeOH extract (340.0 g) was obtained from the rhizomes of Z cassumunar (1.4 kg). An aliquot of the extract was partitioned in an EtOAc–H₂O (1:1, v/v) mixture to furnish an EtOAc-soluble phase (192.9 g, 16.7%) and an H₂O-soluble phase (84.8 g, 7.4%). An aliquot (80.9 g) of the EtOAc-soluble fraction was subjected to normal-phase silica gel CC [2.4 kg, n-hexane-EtOAc → EtOAc → MeOH] to give 6 fractions [Fr. 1, Fr. 2 (15.5 g), Fr. 3 (5.1 g), Fr. 4 (28.6 g), Fr. 5 (10.0 g), Fr. 6 (16.6 g)] as reported previously.^5,6

An aliquot (2.5 g) of Fr. 3 was subjected to reversed-phase silica gel CC [75 g, MeOH–H₂O (70:30 →90:10, v/v) →MeOH] to give eight fractions [Fr. 3-1 (78 mg), Frs. 3-2 to 3-8]. Fr. 3-1 (78 mg) was purified by HPLC [MeOH–H₂O (50:50, v/v)] to give cassumunol K (3, 1.4 mg, 0.00061%) and cassumunol M (5, 6.3 mg, 0.0028%). An aliquot (14.2 g) of Fr. 4 was subjected to reversed-phase silica gel CC [426 g, MeOH–H₂O (50:50 →70:30 →80:20, v/v) → MeOH] to give nine fractions [Fr. 4-1, Fr. 4-2 (183 mg), Fr. 4-3 (126 mg), Frs. 4-4 to 4-9]. An aliquot (93 mg) of Fr. 4-2 was purified by HPLC [MeOH–H₂O (40:60, v/v)] to give cassumunol I (1, 5.8 mg, 0.0047%). Fr. 4-3 (126 mg) was purified by HPLC [MeOH–H₂O (40:60, v/v)] to give cassumunol I (1, 14.7 mg, 0.0061%). An aliquot (8.3 g) of Fr. 6 was subjected to normal-phase silica gel CC [249 g, n-hexane-EtOAc (2:1 →1:1 →1:2 →1:5, v/v)→EtOAc →MeOH] to give 6 fractions [Frs. 6-1 to 6-3, Fr. 6-4 (647 mg), Fr. 6-5 (4.86 g), Fr. 6-6]. Fr. 6-4 (647 mg) was subjected to reversed-phase silica gel CC [19.4 g, MeOH–H₂O (20:80 →40:60 →60:40 →80:20, v/v) → MeOH] to give nine fractions [Fr. 6-4-1, Fr. 6-4-2, Fr. 6-4-3 (44 mg), Frs. 6-4-4 to 6-4-9]. Fr. 6-4-3 (44 mg) was further purified by HPLC [MeOH–H₂O (28:72, v/v)] to give cassumunol J (2, 3.1 mg, 0.0013%). An aliquot (2.63 g) of Fr. 6-5 was subjected to reversed-phase silica gel CC [78.9 g, MeOH–H₂O (10:90 →30:70 →60:40 →80:20, v/v) → MeOH] to give 7 fractions [Fr. 6-5-1 (131 mg), Frs. 6-5-2 to 6-5-7]. Fr. 6-5-1 (131 mg) was further purified by HPLC [MeOH–H₂O (15:85, v/v)] to give cassumunol L (4, 4.1 mg, 0.0031%).

Cassumunol I (1)

Pale yellow oil

[α]²⁴_D: + 12.4 (c 0.45, CHCl₃).

IR (film) v_max: 3450, 2930, 1655, 1474 cm⁻¹.

UV λmax [CHCl₃, nm, (log ε)]: 281 (3.35), 241 (3.55).

¹H NMR (500 MHz, CDCl₃) δ 3.87, 3.88 [3H each, both s, CH₃O-3′, 4′ (interchangeable)], 4.32 (1H, m, H-2), 5.14 (1H, dd, J = 1.4, 10.5 Hz, H-4a), 5.27 (1H, dd, J = 1.4, 17.0 Hz, H-4b), 5.94 (1H, ddd, J = 5.7, 10.5, 17.0 Hz, H-3), 6.76 (1H, d-like, J = 8.9 Hz, H-6′), 6.78 (1H, s-like, H-2′), 6.83 (1H, d, J = 8.9 Hz, H-5′).

¹³C NMR (126 MHz, CDCl₃) δ_c: given in Table 1 and see Supplemental file.

EIMS: m/z 208 (M)⁺; HREIMS m/z 208.1104 [Calcd for C₁₂H₁₆O₃ (M)⁺, 208.1099].

Cassumunol J (2)

Pale yellow oil

[α]²⁷_D: + 7.1 (c 0.16, CHCl₃).

IR (film) v_max: 3450, 2925, 1655, 1465 cm⁻¹.

UV λmax [CHCl₃, nm, (log ε)]: 279 (3.74), 231 (4.19).

¹H NMR (500 MHz, CDCl₃) δ 3.88, 3.89 [3H each, all s, CH₃O-3′, 4′ (interchangeable)], 4.23 (1H, dd-like, J = 5.5, 5.5 Hz, H-2), 4.46 (1H, d, J = 5.5 Hz, H-1), 5.17 (1H, d-like, J = 11.0 Hz, H-4a), 5.28 (1H, d-like, J = 17.1 Hz, H-4b), 5.74 (1H, ddd, J = 5.5, 11.0, 17.1 Hz, H-3), 6.84 (1H, d, J = 8.6 Hz, H-5′), 6.89 (1H, dd, J = 1.8, 8.6 Hz, H-6′), 6.91 (1H, d-like, J = 1.8 Hz, H-2′).

¹³C NMR (126 MHz, CDCl₃) δ_c: given in Table 1 and see Supplemental file.

CIMS: m/z 225 (M + H)⁺; HRCIMS m/z 225.1135 [Calcd for C₁₂H₁₇O₄ (M + H)⁺, 225.1127].

Cassumunol K (3)

Pale yellow oil

[α]²³_D: −7.4 (c 0.11, CHCl₃).

IR (film) v_max: 3450, 2925, 1648, 1509 cm⁻¹.

UV λmax [CHCl₃, nm, (log ε)]: 323 (3.99), 265 (4.18).

¹H NMR (600 MHz, CDCl₃) δ 3.39, 3.84, 3.87, 3.90 (3H each, all s, CH₃O-2, 2′, 5′, 4′), 3.65 (2H, m, H-1), 3.89 (1H, m, H-2), 5.90 (1H, dd, J = 7.8, 15.9 Hz, H-3), 6.50 (1H, s, H-3′), 6.93 (1H, d, J = 15.9 Hz, H-4), 6.98 (1H, s, H-6′).

¹³C NMR (151 MHz, CDCl₃) δ_c: given in Table 1 and see Supplemental file.

EIMS: m/z 268 (M)⁺; HREIMS m/z 268.1302 [Calcd for C₁₄H₂₀O₅ (M)⁺, 268.1310].

Cassumunol L (4)

Pale yellow oil

[α]²⁶_D: + 5.2 (c 0.18, CHCl₃).

IR (film) v_max: 3450, 2962, 1458, 1262, 972, 841 cm⁻¹.

UV λmax [CHCl₃, nm, (log ε)]: 280 (3.35).

¹H NMR (500 MHz, CDCl₃) δ 3.28 (1H, m, H-2), 3.41 (1H, m, H-3), 3.66 (1H, dd, J = 4.3, 12.8 Hz, H-4a), 3.88, 3.90 (s, CH₃O-3′, 4′, interchangeable), 3.94 (1H, dd, J = 1.8, 12.8 Hz, H-4b), 4.88 (1H, d, J = 3.1 Hz, H-1), 6.87 (1H, d, J = 8.6 Hz, H-5′), 6.92 (1H, dd-like, J = 1.7, 8.6 Hz, H-6′), 6.93 (1H, d-like, J = 1.7 Hz, H-2′).

¹³C NMR (126 MHz, CDCl₃) δ_c: given in Table 1 and see Supplemental file.

EIMS: m/z 240 (M)⁺; HREIMS m/z 240.1005 [Calcd for C₁₂H₁₆O₅ (M)⁺, 240.0998].

Cassumunol M (5)

Pale yellow oil

[α]²³_D: + 1.8 (c 0.33, CHCl₃).

IR (film) v_max: 3450, 2940, 1509, 1208, 972, 841 cm⁻¹.

UV λmax [CHCl₃, nm, (log ε)]: 293 (3.69).

¹H NMR (500 MHz, CDCl₃) δ 3.19 (1H, dd, J = 2.4, 6.1 Hz, H-2), 3.24 (1H, dt-like, J = 2.4, 4.3 Hz, H-3), 3.34, 3.80, 3.86, 3.90 (all s, CH₃O-1, 2′, 4′, 5′), 3.55 (1H, dd, J = 4.3, 12.9 Hz, H-4a), 3.88 (1H, m, H-4b), 4.48 (1H, d, J = 6.1 Hz, H-1), 6.53, 6.96 (1H each, both s, H-3′, 6′).

¹³C NMR (126 MHz, CDCl₃) δ_c: given in Table 1 and see Supplemental file.

EIMS: m/z 284 (M)⁺; HREIMS m/z 284.1268 [Calcd for C₁₄H₂₀O₆ (M)⁺, 284.1260].

Preparation of (S)- and (R)-MTPA Esters (1a and 1b) From 1

A solution of 1 (0.8 mg, 0.004 mmol) in pyridine (1.0 mL) was treated with (–)-MTPA-Cl (0.015 mL, 0.08 mmol), and the reaction mixture was stirred at r.t. for 2 h. The reaction mixture was poured into H₂O and extracted with EtOAc. The EtOAc extract was washed with NaCl aqueous solution and then dried over Na₂SO₄ powder and filtered. Removal of the solvent from the filtrate under reduced pressure furnished a residue, which was purified by reversed-phase silica gel CC [MeOH–H₂O (50:50, v/v) → MeOH] to give (S)-MTPA ester (1a, 1.6 mg). Employing a similar procedure, (R)-MTPA ester (1b, 1.3 mg) was obtained from 1 (0.8 mg, 0.004 mmol) using ( + )-MTPA-Cl.

(S)-MTPA ester (1a).

Pale yellow oil

¹H NMR (500 MHz, CDCl₃) δ 2.90 (2H, m, H₂-1), 3.75, 3.85 [3H each, both s, CH₃O-3′, 4′ (interchangeable)], 5.27 (1H, d-like, J = 11.0 Hz, H-4a), 5.37 (1H, d-like, J = 16.5 Hz, H-4b), 5.71 (1H, m, H-2), 5.85 (1H, m, H-3), 6.63 (1H, s-like, H-2′), 6.65 (1H, d, J = 7.8 Hz, H-5′), 6.71 (1H, d-like, J = 7.8 Hz, H-6′).

EIMS: m/z 424 (M)⁺; HREIMS m/z 424.1492 [Calcd for C₂₂H₂₃O₅F₃ [M]⁺, 424.1497].

(R)-MTPA ester (1b)

Pale yellow oil

¹H NMR (500 MHz, CDCl₃) δ 2.96 (2H, m, H₂-1), 3.79, 3.87 [3H each, both s, CH₃O-3′, 4′ (interchangeable)], 5.24 (1H, d-like, J = 10.3 Hz, H-4a), 5.32 (1H, d, J = 17.8 Hz, H-4b), 5.68 (1H, m, H-2), 5.82 (1H, m, H-3), 6.75 (1H, s-like, H-2′), 6.76 (1H, d-like, J = 8.0 Hz, H-5′), 6.80 (1H, d-like, J = 8.0 Hz, H-6′).

EIMS: m/z 424 (M)⁺; HREIMS m/z 424.1502 [Calcd for C₂₂H₂₃O₅F₃ [M]⁺, 424.1497].

Supplemental Material

sj-docx-1-npx-10.1177_1934578X221077823 - Supplemental material for Chemical Structures of Phenylbutanoids From Rhizomes of Zingiber cassumunar

Supplemental material, sj-docx-1-npx-10.1177_1934578X221077823 for Chemical Structures of Phenylbutanoids From Rhizomes of Zingiber cassumunar by Seikou Nakamura, Junko Iwami, Yutana Pongpiriyadacha, Souichi Nakashima, Hisashi Matsuda and Masayuki Yoshikawa in Natural Product Communications

Footnotes

Acknowledgments

This work was supported by JSPS KAKENHI Grant Number 20K07109 (S.N.).

Declaration of Conflicting Interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Ethical Approval

Not applicable, because this article does not contain any studies with human or animal subjects.

Funding

The authors disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This work was supported by the JSPS KAKENHI (grant number 20K07109).

Informed Consent

Not applicable, because this article does not contain any studies with human or animal subjects.

ORCID iD

Seikou Nakamura

Trial Registration

Not applicable, because this article does not contain any clinical trials.

Supplemental Material

Supplemental material for this article is available online.

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