Chemical Constituents from the Roots of Furcraea bedinghausii Koch

Phytochemical investigation of the roots of Furcraea bedinghausii Koch. Led to the isolation of a mixture of two new homoisoflavones, 5,7-dihydroxy-3-(3,4-methylenedioxybenzyl)-chromone (4a) and 5,7-dihydroxy-3-(4-methoxybenzyl)-chromone (4b), together with the known β -sitosterol (1), 7,4'-dihydroxyhomoisoflavane (2), dihydrobonducellin (3), kaempferol (5), 5,7-dihydroxy-3-(4-hydroxybenzyl)-chromone (6), 1-linoleylglycerol (7), 6’-linoleyl-3- O - β -D-glucopyranosyl- β -sitosterol (8), trans -3,3’,5,5’-tetrahydroxy-4’-methoxystilbene (9), yuccaol C (10), yuccaol D (11), 3- O - β -D-glucopyranosyl- β -sitosterol (12), 4-[6- O -(4-hydroxy-3,5-dimethoxybenzoyl)- β -D-glucopyranosyloxy]-3-methoxybenzoic acid (13) and two pairs of steroidal saponins: (25 R )-2 α -3 β – dihydroxy-5 α -spirostan-12-one 3- O - β -D-glucopyranosyl- (1→2) - O -[ β -D-xylopyranosyl- (1→3)] - O - β - D-glucopyranosyl- (1→4) - β -D-galactopyranoside (14a) and (25 R )-2 α -3 β –dihydroxy-5 α -spirost-9-en-12-one 3- O - β -D-glucopyranosyl- (1→2) - O -[ β -D-xylopyranosyl- (1→3)] - O - β -D-glucopyranosyl-(1→4) - β -D-galactopyranoside (14b), (25 R )-3 β –hydroxy-5 α -spirostan-12-one 3- O - β -D-glucopyranosyl- (1→2) - O -[ β -D-xylopyranosyl- (1→3)] - O - β -D-glucopyranosyl- (1→4) - β -D-galactopyranoside (15a) and (25 R )-3 β –hydroxy-5 α -spirost-9-en-12-one 3- O - β -D-glucopyranosyl-(1→2) - O -[ β -D-xylopyranosyl- (1→3)] - O - β -D-glucopyranosyl- (1→4) - β -D-galactopyranoside (15b). Their structures were elucidated by interpretation of spectral data and by comparison with literature.


INTRODUCTION
Furcraea bedinghausii K. Koch (Syn.: Yucca pringlei Greenm) belongs to the Agavaceae family which has more than 580 species widely distributed in tropic and subtropic dry climate regions [1,2]. The genus Furcraea has about 20 species, and is mainly cultivated as ornamental plants. Nevertheless, leaves of some plants of this genus have been used to treat ulcers, venereal diseases, rheumatism and as diuretic. They are also used as a source of fiber and to reduce swelling [3]. To the best of our knowledge, no phytochemical work is reported on Furcraea bedinghausii. However, phytochemical investigations on plants of the genera  LTD, 2013 Furcraea and Yucca afforded steroidal saponins [1,3,4] and phenolic compounds [5,6]. In this paper, the chemical survey of secondary metabolites from the roots of Furcraea bedinghausii was achieved, leading to the isolation and structure elucidation of several compounds including an inseparable mixture of two new homoisoflavones.

1. Plant material
The roots of Furcraea bedinghausii were collected in Dschang (West Region of Cameroon) in October 2009 and was identified at the Cameroon National Herbarium, Yaoundé, where a voucher specimen (Ref: HCN 25568) has been deposited.

3. Extraction and isolation
The dried and pulverized roots of Furcraea bedinghausii (3.5 Kg) were extracted with methanol (2 X 10 L). The filtrate obtained was concentrated under reduced pressure to yield a dark residue (450 g). Part of this extract (430 g) was suspended in water (300 mL) and extracted with EtOAc and n-butanol, yielding after evaporation 24.6 g and 55 g of dried extracts, respectively. A portion of the EtOAc extract (21.6 g) was subjected to column chromatography over silica gel eluted with n-hexane-EtOAc and EtOAc-MeOH with increasing polarity, yielding seven main fractions (A-G). Recrystallization and filtration of fraction B (2.53 g) yielded compound 1 (250 mg) and the filtrate obtained was chromatographed on Sephadex LH-20 column eluted with CH 2 Cl 2 -MeOH (1:1) to afford compound 2 (15 mg) and a subfraction.

10
ILCPA Volume 16 column eluted with MeOH to afford compounds 10 (25 mg) and 11 (47 mg). Recrystallization and filtration of fraction G (3.21 g) yielded mainly compound 12 (340 mg). The n-BuOH extract (50 g) was subjected to a silica gel column chromatography using the mixture EtOAc-MeOH with increasing amount of MeOH as eluent to yield four main fractions I-IV. From fraction I (8.3 g), compound 12 (510 mg) was obtained after recrystallization in MeOH. Fraction II (7.1 g) was first submitted to a Sephadex column eluted with MeOH, then to silica gel column chromatography eluted with EtOAc-MeOH-H 2 O (95:5:2) to afford compound 13 (50 mg).

RESULTS AND DISCUSSION
Column chromatography of the EtOAc and n-butanol soluble fractions of the MeOH extract from the dried roots of Furcraea bedinghausii led to the isolation and structure elucidation of a mixture of two new homoisoflavonoids together with the known β-sitosterol (1) [7], 7,4'-dihydroxy-homoisoflavane (2) [16] were isolated from the roots of Furcraea bedinghausii Koch (Fig. 1).
Compound 4 was obtained as yellow oil in hexane-EtOAc 7:3. It appeared as a mixture of two compounds 4a and 4b despite repeated column chromatography on Sephadex and silica gel and the apparent homogeneity on TLC. The
The 1 H and 13 C-NMR spectra showed a set of duplicated signals corresponding to the common parts of the molecules. However, significant differences were observed, especially for signals corresponding to the B ring. The 1 H-NMR spectrum showed two deshielded proton signals at δ 12.73 and 12.76 ppm corresponding to the chelated protons 5-OH in compounds 4a and 4b, respectively ( Table 1).
Additionally, it exhibited proton signals at δ 6.31, 6.30, 6.26 and 6.25 ppm, giving correlations in the HSQC spectrum with carbons at δ 93.9, 93.9, 99.3 and 99.5 ppm, characteristic of two homoisoflavonoid units having the C-5 and C-7 dioxygenation patterns [11]. families [23,24]. The stilbenoid trans-3,3',5,5'-tetrahydroxy-4'-methoxystilbene (9) isolated during this work was also obtained from Yucca schidigera [5,25] and Yucca periculosa [26]. Yuccaols A-E isolated from Yucca schidigera [25] possess a very rare spiro-structure. During our investigation on Furcraea bedinghausii (Yucca pringlei), yuccaols C (10) and D (11) were obtained. In comparison of the results obtained from Furcraea bedinghausii with those obtained from other Agavaceae species, steroidal saponins, homoisoflavonoids and yuccaols could be considered as the chemotaxonomic markers for the family Agavaceae. To the best of our knowledge, this is the first report on the isolation of homoisoflavonoids in a plant of the genera Furcraea and Yucca.