Isolation and Biological Activity of Antibacterial Compounds from C. erythrophyllum
C. erythrophyllum leaf extracts were examined in more detail and seven antibacteri-
al compounds were isolated. Four of these compounds were identified as flavo-
nols, namely 5,6,4′-trihydroxyflavonol (kaempferol), 5,4′-dihydroxy-7-methoxyflav-
onol (rhamnocitrin), 5,4′-dihydroxy-7,5′-dimethoxyflavonol (rhamnazin), and 7,4′-
dihydroxy-5,5′-dimethoxyflavonol (quercetin-5,3′-dimethylether) and three were
identified as flavones, namely 5,7,4′-trihydroxyflavone (apigenin), 5,4′-dihydroxy-7-
methoxyflavone (genkwanin), and 5-hydroxy-7,4′-dimethoxyflavone. Six of these
flavonoids were reported for the first time in Combretaceae. Isolated compounds
were identified using nuclear magnetic resonance (NMR) and mass spectroscopy
(MS). Rf values of the flavonoids in three TLC solvent systems were provided to fa-
cilitate dereplication [26].
The biological activity of five of these compounds was examined in more detail.
All had good activity against Vibrio cholerae and Enterococcus faecalis, with MIC val-
ues in the range of 25–50 μg mL–1. Rhamnocitrin and quercetin-5,3′-dimethyleth-
er also inhibited Micrococcus luteus and Shigella sonei at 25 μg mL–1. With the excep-
tion of 5-hydroxy-7,4′-dimethoxy-flavone, the flavonoids were not toxic towards hu-
man lymphocytes. This compound is potentially toxic to human cells and exhibit-
ed the poorest antioxidant activity whereas rhamnocitrin and rhamnazin exhibited
strong antioxidant activity. Genkwanin, rhamnocitrin, quercetin-5,3′-dimethyleth-
er, and rhamnazin had higher anti-inflammatory activity than the positive control
mefenamic acid. Although these flavonoids are known, this is the first report of bi-
ological activity with several of these compounds.
C. erythrophyllum leaf extracts were examined in more detail and seven antibacteri-
al compounds were isolated. Four of these compounds were identified as flavo-
nols, namely 5,6,4′-trihydroxyflavonol (kaempferol), 5,4′-dihydroxy-7-methoxyflav-
onol (rhamnocitrin), 5,4′-dihydroxy-7,5′-dimethoxyflavonol (rhamnazin), and 7,4′-
dihydroxy-5,5′-dimethoxyflavonol (quercetin-5,3′-dimethylether) and three were
identified as flavones, namely 5,7,4′-trihydroxyflavone (apigenin), 5,4′-dihydroxy-7-
methoxyflavone (genkwanin), and 5-hydroxy-7,4′-dimethoxyflavone. Six of these
flavonoids were reported for the first time in Combretaceae. Isolated compounds
were identified using nuclear magnetic resonance (NMR) and mass spectroscopy
(MS). Rf values of the flavonoids in three TLC solvent systems were provided to fa-
cilitate dereplication [26].
The biological activity of five of these compounds was examined in more detail.
All had good activity against Vibrio cholerae and Enterococcus faecalis, with MIC val-
ues in the range of 25–50 μg mL–1. Rhamnocitrin and quercetin-5,3′-dimethyleth-
er also inhibited Micrococcus luteus and Shigella sonei at 25 μg mL–1. With the excep-
tion of 5-hydroxy-7,4′-dimethoxy-flavone, the flavonoids were not toxic towards hu-
man lymphocytes. This compound is potentially toxic to human cells and exhibit-
ed the poorest antioxidant activity whereas rhamnocitrin and rhamnazin exhibited
strong antioxidant activity. Genkwanin, rhamnocitrin, quercetin-5,3′-dimethyleth-
er, and rhamnazin had higher anti-inflammatory activity than the positive control
mefenamic acid. Although these flavonoids are known, this is the first report of bi-
ological activity with several of these compounds.
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