Ixorine, a New Cyclopeptide Alkaloid from the Branches of <i>Ixora brevifolia</i>

Medina, Rebeca P.; Schuquel, Ivânia T. A.; Pomini, Armando M.; Silva, Cleuza C.; Oliveira, Cecília M. A.; Kato, Lucília; Nakamura, Celso V.; Santin, Silvana M. O.

doi:10.5935/0103-5053.20150326

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Journal of the Brazilian Chemical Society

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Articles • J. Braz. Chem. Soc. 27 (4) • Apr 2016 • https://doi.org/10.5935/0103-5053.20150326 copy

Ixorine, a New Cyclopeptide Alkaloid from the Branches of Ixora brevifolia

Authorship SCIMAGO INSTITUTIONS RANKINGS

The isolation and structure determination of new cyclic peptide alkaloid ixorine, along with five known constituents frangulanine, syringaresinol, cinnamtannin B-1, daucosterol and mannitol from the branches of Ixora brevifolia are described. The cyclic peptide frangulanine is being described for the first time in the Rubiaceae family. The structures were elucidated on their spectral data basis, mainly one- (¹H, ¹³C, DEPT) and two-dimensional (COSY, NOESY, HSQC and HMBC) nuclear magnetic resonance (NMR) and by comparison with data from the literature. The mixture of two cyclopeptide alkaloids showed weak activity against Leishmania amazonensis.

Keywords:
Ixora brevifolia; Rubiaceae; cyclopeptide alkaloids; Leishmania

Position	δ_C	δ_H (mult., J in Hz)	HMBC	COSY
1	156.3	−	H-14, H-16	−
2	−	−	−	−
3	81.7	4.91 (dd, 8.0, 2.1)	H-4, H-18, H-19	H-4
4	55.6	4.44 (dd, 9.0, 8.0)	−	H-20 (NH)
5	171.6	−	H-6 (NH)	−
6	−	5.94 (d, 6.3, NH)	−	−
7	55.2	4.30 (m)	H-28	H-28
8	167.2	−	H-28	−
9	−	6.20 (sl, NH)	−	−
10	125.7	6.56 (m)	−	−
11	118.4	6.40 (d, 6.6)	H-13	−
12	131.8	−	H-14	−
13	131.7	7.03 (m)	−	H-14
14	121.9	7.15 (m)	−	−
15	122.7	7.03 (m)	−	H-16
16	130.2	6.92 (m)	−	−
17	29.3	2.00 (m)	H-18, H-19	H-18, H-19
18	20.4	1.25 (d, 7.2)	H-17, H-19	−
19	15.2	1.00 (d, 6.6)	H-17	−
20	−	6.94 (m, NH)	−	−
21	172.4	−	H-22, H-23	−
22	75.2	2.40 (d, 4.2)	H-24, H-25, H-26, H-27	H-26, H-27
23	27.8	2.05 (m)	H-24, H-25	H-24, H-25
24	21.0	1.05 (d, 6.9)	−	−
25	17.6	0.93 (d, 6.6)	−	−
26	43.1	2.14 (s)	H-27	−
27	43.1	2.14 (s)	−	−
28	37.1	2.76 (dd, 13.8, 4.5)/3.07 (m)	H-30, H-30’	H-28
29	135.7	−	H-7, H-28, H-31, H-31’	−
30, 30’	129.6	7.15 (m)	−	H-31, H-31’
31, 31’	129.0	7.34 (m)	−	−
32	127.4	7.24 (m)	−	H-30, H-30’

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