Ruta angustifolia (L.) Pers. is a Rutaceous species which contains various anthranilic acid derived alkaloids including
the bioactive quinolones. This study is aimed at identifying the antimicrobial active alkaloids of R. angustifolia and
evaluating their potential as synergistic enhancers in alkaloid-antibiotic combinations. Antimicrobial bioautographyguided isolation of alkaloidal fractions of R. angustifolia leaves has led to the identification of 2,3-dimethoxy-1-hydroxy10-methylacridone [arborinine]; and 4,7,8-trimethoxyfuro[2,3-b]quinoline [skimmianine]; together with the major
active alkaloid, 1-methyl-2-[3’,4’-methylenedioxyphenyl]-4-quinolone [graveoline]. Graveoline showed Minimum
Inhibitory Concentration (MIC) values ranging from 500 to 1000 µg/mL against Staphylococcus aureus ATCC 25923,
Enterococcus faecalis ATCC 29212 and Escherichia coli ATCC 25922. Checkerboard assay for antimicrobial combination
effects between graveoline with either erythromycin or vancomycin showed enhancement of the antimicrobial activity
of both antibiotics with Fractional Inhibitory Concentration Indices (FICI) ranged from 0.37 to 1.50. Synergistic effect
with FICI of 0.37 was observed for graveoline-erythromycin combination against S. aureus compared to FICI of 1.00 for
ciprofloxacin-erythromycin additive effect. Graveoline was a potential candidate for antimicrobial combination agent
especially against S. aureus. The result supports the idea of using plant metabolites as antimicrobial synergistic agents.
This study was performed to evaluate the antifungal activities of methanolic fractions from the stem bark of Entada spiralis Ridl. against human dermatophytes and yeast-like fungus in vitro. Three types of human dermatophyte, Trichophyton mentagrophytes ATCC 9533, Microsporum gypseum ATCC 24102 and Trichophyton tonsurans ATCC 28942, and one yeast-like fungus, Candida glabrata ATCC 66032, were tested against the methanolic fractions labelled FA1, FA4 and FA5. T. mentagrophytes, T. tonsuran and M. gypseum were susceptible to all tested fractions in a concentration-dependent manner whereas C. glabrata was resistant. Fraction FA1 at a concentration of 400 mg/mL was found to exhibit the highest antifungal activity with the inhibition zone diameter of 22 mm (T. mentagrophytes). This fraction showed a minimum inhibitory concentration MIC of 0.097 mg/mL while the MIC value for the fraction FA4 and fraction FA5 was 3.12 mg/ml and 1.56 mg/ml respectively. Agar overlay bioautography assay results showed that most of the bioactive compounds were found in the fraction FA1. Based on these findings, it can be concluded that the stem bark extracts of E. spiralis can be a future source of potent natural antimicrobial drugs for superficial skin diseases.
Antibacterial activity of different types of P. odorata leaf extracts was evaluated in combination with
standard antibiotics. Persicaria. odorata leaves were extracted with n-hexane (n-hex), dichloromethane
(DCM) and methanol (MeOH). Each extract was applied on vancomycin (30µg), erythromycin (15µg) and
gentamicin (10µg) discs, respectively. Disk diffusion method was used to evaluate the synergistic activity of
each combination on Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus pyogenes,
Streptococcus pneumoniae, Pseudomonas aeruginosa, Salmonella typhi, and Escherichia coli. Minimum
inhibitory concentration (MIC) and gas chromatography mass spectrometry (GCMS) analysis was performed on
the active extract. Synergistic effects seen were mainly from the n-hex+antibiotics combinations, mainly on
the Gram-positive bacteria (7 additive, 5 antagonistic), with MIC range from 50 µg/ml to 100 µg/ml, as well
as Gram-negative bacteria (2 additive, 2 indifferent, 5 antagonistic). In particular, synergism showed by the
combination of n-hex+van were all additive against the susceptible bacteria. DCM extract combination
showed synergistic effects on three Gram-positive species (S. aureus, S. epidermidis, S. pyogenes).
Meanwhile, MeOH+antibiotics combination showed significant additive synergistic effects (p