1. Phytochemical investigation of Eriosema laurentii
Sylvin Benjamin Atebaa,b, Dieudonné Njamena, Martin Zehlb, Katrin Ukowitzb, Hanspeter Kähligc, Liselotte Krennb
aDepartment of Animal Biology and Physiology, University of Yaounde I, P.O. Box 812 Yaounde, Cameroon
bDepartment of Pharmacognosy, University of Vienna, Althanstraße 14, A-1090 Vienna, Austria
cInstitut of Organic Chemistry, University of Vienna, Währingerstraße 38, A-1090 Vienna, Austria
Eriosema laurentii De Wild (Leguminosae) is a herbaceous or semi-woody shrub of up to 1.5 m height. It is widely distributed in West and Central Africa where it is used as food and medicine [1], e.g. in Cameroon for the treatment of infertility and various gynecological and menopausal problems. Despite this use as natural remedy, a phytochemical analysis of this plant has not been carried out, yet. Therefore, based on the traditional claims, a thorough phytochemical investigation of E. laurentii was undertaken aiming to identify estrogenic compounds.
Introduction
2’-Hydroxygenistein
Eriosemaon D
Compound I
Compound II
Isovitexin Homoorientin
Genistin ’-Hydroxygenistein
Luteolin-7-O-glucoside
Isolation
Fractionation by VLC on silica gel
Liquid-liquid partition with water andCHCl3/isopropanol
Aerial parts
Extraction with 95% MeOH
Methanol extract
CHCl3/MeOH fraction
Petroleum ether fraction
Non soluble fraction
Water fraction
CC on Sephadex LH-20
Liquid-liquid partition with water and n-Butanol
n-Butanol fraction
CHCl3/isopropanol fraction
Genistein Luteolin
Lupinalbin A Quercetin
Quercetin-3-methyl-ether
Underground parts
Successive HPCCC
Water soluble fraction
Genistin
1-Extraction with water
2-Liquid-liquid partition with water and CHCl3/isopropanol
Liquid-liquid partition with water and petroleum ether
Saccharose
Glucose
Fructose
2’-Hydroxygenistein
Lupinalbin A
Eriosemaon D
LC-MS, 1H-NMR and 13C-NMR in good correlation to published data [2-4]
LC-MS, 1H-NMR , 13C-NMR and 2D-NMR techniques (HMBC, HSQC, DQF-COSY and NOESY)
6,8,3'-Triprenyl-dihydromorin (II)
5,7-Dihydroxy-2'-methoxy-6",6"-dimethyl-pyrano(2",3": 4',5') isoflavone (I)
Structure elucidation
Genistin Genistein
Homoorientin Quercetin
Luteolin-7-O-glucoside Isovitexin
Quercetin-3-methyl-ether Luteolin
TLC with two different systems, RP-HPLC and LC-MS with authentic substances
Two new compounds: 5,7-dihydroxy-2'-methoxy-6",6"-dimethyl-pyrano(2",3": 4',5')isoflavone (I) and the highly prenylated 6,8,3'-triprenyl-dihydromorin (II) were isolated and structurally elucidated. Eleven known flavonoids/isoflavonoids were identified as genistein, genistin, 2’-hydroxygenistein, lupinalbin A, luteolin, luteolin-7-O-glucoside, homoorientin, quercetin, quercetin-3-O-methylether, isovitexin and eriosemaon D for the first time in E. laurentii.
These results proved the occurrence of several phytoestrogens in E. laurentii which contribute to the activity and support the traditional use of this plant against infertility and in menopausal problems.
Results and Conclusion
Position
13C (ppm)
1H (ppm)
JH,H (Hz) 2 3 4 5 6 7 8 9 10 1ʹ 2ʹ 3ʹ 4ʹ 5ʹ 6ʹ
3ʹa
3ʹb
3ʹc
3ʹd
3ʹe 6a 6b 6c 6d 6e 8a 8b 8c 8d 8e CH C
CH2
CH3
80.57
73.48
199.10
160.15
109.92
163.59
109.04
159.36
101.96
117.01
155.36
117.59
157.55
108.34
126.72
23.42
124.32
131.76
a 17.97
b 25.98
22.14
123.57 c
a 17.93
22.64
123.42 c
a 17.89
b 25.95
5.318
4.616
----
6.436
7.123
3.375
5.238
1.775
1.665
3.286
5.164
1.770
1.670
3.219
5.099
1.535
1.625
d 11.7
d 8.4
d 7.0 m
Position
13C (ppm)
1H (ppm)
JH,H (Hz) 2 3 4 5 6 7 8 9 10 1ʹ 2ʹ 3ʹ 4ʹ 5ʹ 6ʹ
4ʹʹ
5ʹʹ
6ʹʹ CH C
OCH3
CH3
156.39
122.15
182.20
163.69
100.22
166.14
94.92
159.80
106.14
113.31
160.06
56.27
101.08
156.21
115.44
130.28
122.70
129.20
77.76
28.36
7.919
----
6.215
6.332
3.744
6.473
6.895
6.305
5.545
1.413 s
d 2.2
d 9.8
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References
Ateba SB received an “Ernst-Mach-Stipendium” granted by OeAD, financed by BMWF and a travel grant from ÖPhG. The work was also supported by a grant from “Gesellschaft zur Förderung für Pflanzenwissenschaften” (Austria).
Acknowledgements
Trends in natural products research: a young scientists meeting of PSE and ÖPhG, July 2013, Obergurgl/Tyrol, Austria