The extractives from Sophora velutina and Calpurnia aurea and their biological activity.
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Date
2012
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Abstract
This work is an account of the phytochemistry and biological activity of two related plant species
within the plant family the Fabaceae, Sophora velutina from the subtribe Sophoreae and
Calpurnia aurea of the subtribe Podalyrieae. Members of this family are known to contain
quinolizidine alkaloids and flavonoids, which are chemotaxonomic markers in the Fabaceae.
The phytochemical investigation of Sophora velutina resulted in the isolation of ten compounds,
including five novel quinolizidine alkaloids, N-methylenehydroxycytisine (A-1), 7-
hydroxylupanine (A-2), 6,7-dihydroxylupanine (A-3) and 17-oxo-thermopsine (A-4) from the
fruits and velutinine (A-5) from the bark along with the known quinolizidine alkaloids Nmethylcytisine
(A-6) and cytisine (A-7), and a cinnamate ester, methyl-3-(3',4'-
dimethoxyphenyl)-2-propenoate (A-8) and triterpenoids lup-20(29)-ene-3β-ol (A-9) and 12-
oleanen-3-one (A-10). The isolated compounds were tested for their antibacterial activity
against Enterococcus faecalis and Pseudomonas aeruginosa. P. aeruginosa showed resistance
against eight of the ten samples tested with only the cinnamate ester and the steroid 12-oleanen-
3-one (A-10) being slightly active at 200 and 175 μg mL-1, respectively. However, the
quinolizidine alkaloid, N-methylcytisine (A-6) and 12-oleanen-3-one (A-10) showed good
antibacterial activity against E. faecalis, with MIC values of 20.8 and 10.9 μg mL-1, respectively,
with 17-oxo-thermopsine (A-4), another quinolizidine alkaloid, and the cinnamate ester showing
moderate antibacterial activity against E. faecalis at concentrations of 125 μg mL-1 and 100 μg
mL-1, respectively.
Calpurnia aurea yielded five isoflavones, 4′,5,7-trihydroxyisoflavone (B-1), 7,3′-dihydroxy-5′-
methoxyisoflavone (B-2), 7-hydroxy-4′,8-dimethoxyisoflavone (B-3), 7-acetoxy-4′,8-
dimethoxyisoflavone (B-4) and 3',7-dihydroxy-4′,8-dimethoxyisoflavone (B-5), a pterocarpan (3-
acetoxy-9-methoxypterocarpan) (B-6) and a quinolizidine alkaloid (calpurnine) (B-7) all of
which were isolated from the stem and bark. These isoflavones were screened for in vitro
anticancer activity against breast (MCF7), renal (TK10) and melanoma (UACC62) human cell
lines, where 3',7-dihydroxy-4′,8-dimethoxyisoflavone (B-5) was found to be the most active
amongst all the compounds tested, followed by 3',7-dihydroxy-5'-methoxyisoflavone (B-2), also
with a hydroxyl and methoxy group on the phenyl ring but in the 3' and 5' positions, respectively.
Elucidation of the compounds was done mainly by 1D and 2D NMR spectroscopy together with
mass spectrometry, infrared, and ultraviolet spectroscopy. Antibacterial and anticancer assays
were carried out using standard assays at the Centre for Scientific and Industrial Research
(CSIR), Pretoria, South Africa.
Description
Ph. D. University of KwaZulu-Natal, Durban 2012.
Keywords
Phytochemicals., Angiosperms., Legumes., Plant physiology., Alkaloids., Flavonoids., Theses--Chemistry.