Vol. 21, No. 12, 2010
Cornelius et al.
2213
1
Results and Discussion
data.21-25 The integration of the H NMR signals allowed
us to calculate the approximate relative percentage of both
compounds: 36.16% of 8 and 63.84% of 9.
FromthetrichomesisolatedfromgreenfruitsofSolanum
crinitum Lam were isolated the flavonoids: tiliroside (1),
astragalin (2), kaempferol (3), and biochanin A-7-O-b-
D-apiofuranosyl-(1→5)-b-D-apiofuranosyl-(1→6)-b-D-
glucopyranoside (7), cis- (10) and trans- (11) cumaric
acids and ethyl cis- (8) and trans- (9) cumarate esters and
4-hydroxybenzoic acid (12); from green fruits methanolic
extracts were isolated three tri-glycosyl-steroidal alkaloids,
solamargine (13), 20-epi-solamargine (14) and solasonine
(16). The derivatives 3,5,7,4’-tetramethylkaempferol
(4), 3,7,4’-trimethylkaempferol (5), 3,7,4’-trimethyl-5-
acetylkaempferol (6), the peracetyl-20-epi-solamargine
(15) and peracetyl-solasonine (17) were prepared. The
structures were established on the basis of IR, NMR and
MS data analysis of the natural compounds and of the
derivatives 4-6, 15 and 17.
The fractions containing compounds 13, 14 and 16
showed a positive test for alkaloids. The detailed analysis
of the 1H and 13C NMR spectra of the isolated compounds
allowed to identify characteristic signals corresponding to
the same aglycone as that of the steroidal spirazolane-type
alkaloid in the three glycoalkaloids: four quaternary carbon
atoms, including one linked to oxygen and nitrogen atoms:
(dC 98.7 to 98.5 and one sp2 at dC 141.2 to 140.4), nine
methine groups (including two oxygenated atdC 78.5 to 78.0
and 81.1 to 78.6), ten methylene groups and four methyl
groups = (C)3(O-C-NH)(CH)7 (HC-O)2(CH2)10(CH3)4 =
C27H42NO3 = C27H42NO2 considering the presence of an
ether function (Table 1) having a trisaccharide moiety
(three anomeric carbon atoms: dC 100.6 to 100.3) attached
to the oxygen atom of carbon CH-3, with dC 78.5 to 78.0
(Table 1 and 2), which is significantly higher when
compared with the 13C chemical shift of the methyl carbon
CH-3 sustaining free hydroxyl group (about dC 71).
Compounds 1-3 were identified by the analysis of
13
1H and C NMR spectra, including HMQC and HMBC
experiments, and comparison with literature data for
tiliroside, kaempferol and astragalin.15-18 The first report
of 1 in Solanum species was made by Souza et al.14
Kaempferol and astragalin have been isolated from some
Solanum species.8 The treatment of 3 with diazomethane
yielded the methyl derivatives 4 and 5, described in the
literature,19 and the derivative 6 was obtained by treating
5 with Ac2O/Pyridine. The 2D NMR spectra, including
NOESY experiments, of these derivatives were used to
confirm the proposed structure of 3 and to carry out the
complete assignment of the 1H and 13C chemical shifts of
6 (see Experimental).
The 1H and 13C NMR spectra of compound 7 revealed
characteristic resonances of the isoflavonoid biochanin
A besides additional signals for three sugars unities, one
glucopyranoside and two apiofuranosides. Comparison
of these data with those of glycosides isolated from
Dalbergia nigra20 and Andira anthelmia,21 besides the
analysis of mass spectrum obtained by FAB-MS in
positive mode {m/z 733.20820 ([M+Na]+, C32H38O18+Na+,
calc.: m/z 733.19558), m/z 601.12300 [M+Na-132]+, m/z
451.0600 (M+Na-282)+, m/z 449.27710 [M+Na-284]+, m/z
431.16210 [M+Na-302]+, m/z 317.1338 [M+Na-416]+, m/z
287.0865 [M+Na-446]+}, led us to identify the compound
as biochanin A, 7-O-b-D-apiofuranosyl-(1→5)-b-D-
apiofuranosyl-(1→6)-b-D-glucopyranoside (7). This is
the first report of this apiofuranosyl derivative in Solanum
species.
The H and 13C chemical shifts of the trisaccharide
1
moieties of 13 and 14, had practically the same values
(Table 2), indicating identical the partial structure O-[a-
L-rhamnopyranosyl-(1→2)-O-[a-L-rhamnopyranosyl-
(1→4)]-b-D-glucopyranoside = C18H32O13 (three degrees
of unsaturation, C18H38O13 – C18H32O13 = H6). On the other
hand, the 1H and 13C signals observed in NMR spectra of
16 allowed to characterize the trisaccharide as O-[a-L-
rhamnopyranosyl-(1→2)-O-[b-glucopyranosyl-(1→3)]-
b-D-galactopyranoside = C18H32O14 (three degrees of
unsaturation, C18H38O14 – C18H32O14 = H6). All these NMR
spectral data allowed to deduce the same molecular formulas
C45H73NO15 to 13 and 14 and C45H73NO16 to 16, all with
ten degrees of unsaturation corresponding to one double
bond and six rings). In fact, the values of pseudomolecular
peaks in the positive HRMS spectra at m/z 868.5239
(M + H•+, 100%) of 13 (C45H74NO15 = m/z 868.5058) and
at m/z 868.5305 (M + H•+, 100%) of 14 (C45H74NO15 = m/z
868.5058), besides additional peaks compatible with loss
of sugar moieties, were used to confirm the molecular
formula of these isomeric compounds (13 and 14). The
1
hydrogen and carbon atoms signals observed in the H
and 13C NMR spectra of 13-17 (Tables 1 and 3) were also
assigned with aid of the homonuclear 2D 1H-1H-COSY and
heteronuclear 2D HMQC (1H-13C-COSY-1JCH) and HMBC
(1H-13C-COSY-nJCH, n = 2 and 3), allowing to identify the 1H
chemical shifts of the methyl group signals of the aglycone
and of the trisaccharide moieties (Table 3 and 4): dH 0.83
(d, 3H-27), 0.88 (s, 3H-18), 1.07 (s, 3H-19) and 1.09 (d,
3H-21) of 13, 0.79 (d, 3H-27), 0.85 (s, 3H-18), 1.06 (s,
1
Compounds 8-12 were identified by the H and
13C NMR spectral data analysis of the mixtures of 8+9,
10+11 and of 12 along with comparison with literature