Antibacterial activity of Aquilaria crassna leaf extract against Staphylococcus epidermidis by disruption of cell wall

Abstract

BackgroundAquilaria crassna Pierre ex Lecomte has been traditionally used in Thailand for treatment of infectious diseases such as diarrhoea and skin diseases for a long time. The main objectives of this study were to examine antibacterial activity of the Aquilaria crassna leaf extract against Staphylococcus epidermidis and its underlying mechanism. The antioxidant activity and acute toxicity were studied as well.MethodsAntioxidant activities were examined by FRAP, ABTS and DPPH scavenging methods. Antibacterial activity was conducted using disc diffusion assay and the minimum inhibitory concentration (MIC) was determined by dilution method. The minimum bactericidal concentration (MBC) was reported as the lowest concentration producing no growth of microbes in the subcultures. Morphological changes of the microbe were observed by scanning electron microscopy, while an inhibitory effect on biofilm formation was evaluated by phase contrast microscopic analysis. Bacterial cell wall integrity was assessed by transmission electron microscopy. Acute toxicity was conducted in accordance with the OECD for Testing of Chemicals (2001) guidelines.ResultsThe extract exhibited considerable antioxidant activity. Staphylococcus epidermidis was susceptible to the extract with the MIC and MBC of 6 and 12 mg/ml, respectively. The extract caused swelling and distortion of bacterial cells and inhibited bacterial biofilm formation. Rupture of bacterial cell wall occurred after treated with the extract for 24 h. Acute toxicity test in mice showed no sign of toxicity or death at the doses of 2,000 and 15,000 mg/kg body weight.ConclusionThe aqueous extract of Aquilaria crassna leaves possesses an in vitro antibacterial activity against Staphylococcus epidermidis, with no sign of acute oral toxicity in mice, probably by interfering with bacterial cell wall synthesis and inhibiting biofilm formation.

Evaluation of antibacterial and antioxidant activity of extracts of eelgrass Zostera marina Linnaeus

“…In the present study, extracts of Z. marina L., especially the ethyl acetate fraction, showed good antibacterial activity against Gram positive bacteria, but had no effect on Gram negative bacteria. The antibacterial activity of ethyl acetate fraction against S. aureus is higher than that of ethanol extract of Ecballium elaterium (Adwan et al, 2011), but the activity against S. epidermidis is little lower than that of water extract of Aquilaria crassna (Kamonwannasit et al, 2013). B. anthracis is much more sensitive to ethyl acetate fraction of Z. marina L. than that of stem bark crude extract of Antidesma venosum (Mwangomo et al, 2012).…”

Improvement of in vitro embryo maturation, plantlet regeneration and transformation efficiency from alfalfa (Medicago sativa L.) somatic embryos using Cuscuta campestris extract

“…Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of aqueous, ethanolic and methanolic extracts were determined by serial dilution method (Kamonwannasit et al 2013). To determine MIC, extract dilution series of 20 to 300 mg ml -1 were prepared.…”

Mass Proportion, Bioactive Compounds and Antioxidant Capacity of Carrot Peel as Affected by Various Solvents

“…Table 2 illustrates a strong correlation between saponins of carrot peel and ARSC (R 2 = 0.78), while TPC of carrot peel weakly correlated with ARSC (R 2 = 0.25), meaning that saponins were a major contributor to ARSC of carrot peel, which might promote single electron transfer capacity for ABTS free radical to form an electron pair [17]. The study of Dhanani et al [35] indicated that the ethanolic extract of W. somnifera possessed the highest ARSC in comparison with the extracts obtained by 10% ethanol and water, while the study of Kamonwannasit et al [36] found that the water extract of A. crassna leaves substantially exhibited the ARSC (IC 50 = 218.93 µg/mL) when compared to butylated hydroxytoluene (BHT; IC 50 = 83.09 µg/mL). These results showed that solvents significantly affected ARSC of carrot peel, in which water was the best solvent for obtaining the optimal ARSC from carrot peel.…”