J.C. Ndom et al. / Phytochemistry Letters 3 (2010) 201–206
205
26–52 gave ent-7-oxo-16
(30.5 mg).
a
,17-dihydroxykauran-19-oic acid
2
for yeast (Espinel-Ingroff and Pfaller, 1995). The minimal inhibitory
concentration (MIC) values were taken as the lowest concentration
of all the compounds that inhibited the visible growth of the
organisms on agar after 24 h of incubation at 37 8C (bacteria) and
Fraction D was chromatographed over a silica gel 60 column
with CH2Cl2–MeOH. A total of 30 fractions of ca. 100 mL each were
collected and combined on the basis of TLC. Fractions 1–9 were
further chromatographed over silica gel column with the mixture
of CH2Cl2–MeOH (4:1) and a cream jelly like substance was
obtained. The mixture was subjected to prep TLC with CH2Cl2–
48 h at 28 8C for (yeast). Those with MIC values of 8
mg/mL or below
against any of the bacteria tested, were considered active.
Acknowledgments
MeOH (4:1) to yield steppogenin 40-O-
b-D-glucoside 6 (10 mg).
This investigation was supported by a research grant (RGA) N8.
05-305 RG/CHE/AF/AC to J.C. Ndom from the Third World Academy
of Science (TWAS). We are also grateful to Royal Society for a
visiting fellowship, to the Organic Chemistry Department of the
University of Reading for recording the NMR measurements and
Mass spectra and to Mr. Sameza at the University of Douala for
evaluating the Antibacterial activity.
3.4. Methanolysis of compounds 1
Compound 1 (6.0 mg) were added to a mixture of HCl (3.0 mL,
1N) and dry MeOH (5.5 mg) and refluxed for 16 h with magnetic
stirring. Then H2O (10.0 mL) was added to the refluxed mixture,
which was extracted with n-hexane (2 ꢁ 10 mL). The fatty acid
methyl esters 1a (3.0 mg) were obtained after the purification of
the n-hexane extract over a silica gel column with n-hexane–CHCl3
(9:1) as solvent.
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dissolved in dimethyl sulfoxide (DMSO) at concentration of 5
mg/
mL as well as the control at 5 g/mL. Further dilution was
m
performed using sterile distilled water. Final concentrations of
DMSO in the test were less than 2% (v/v). Two fold serial Mueller-
Hinton agar medium (Merck) for the bacteria and Sabouraud
dextrose agar medium (Merck) for the yeast were used to achieve a
final volume and concentrations ranging from 8 to 0.312
well as the control in the range of 125–0.5 g/mL.
mg/mL as
m
Drugs (Ciprofloxacin, and Amphotericin-B) (Sigma) as well as
growth and blank (medium and solvent 2% v/v) controls were
added to each test. The microbial inoculum sizes were
1.5 ꢁ 106 cells/ml for bacteria (Villanova, 1993) and 106 cells/mL