Nuannoi Chudapongse

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

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.

Effects of Phyllanthus urinaria extract on HepG2 cell viability and oxidative phosphorylation by isolated rat liver mitochondria

ETHNOPHARMACOLOGICAL RELEVANCE Phyllanthus urinaria is widely used as anti-inflammatory, anti-diarrheal and hepatoprotective medicines in Asian countries such as India, China and Thailand. In Thailand, Phyllanthus urinaria is traditionally used as an adjuvant or alternative medicine for cancer patients, including liver cancer. However, there is limited scientific evidence supporting its use in cancer particularly hepatocellular carcinoma. AIM OF THE STUDY To investigate the cytotoxic effect of Phyllanthus urinaria extract on human hepatocellular carcinoma HepG2 cells and the effect on oxidative phosphorylation by isolated rat liver mitochondria. MATERIALS AND METHODS HepG2 cells and isolated rat liver mitochondria were treated with the 50% methanolic extract of Phyllanthus urinaria. Cytotoxicity of the extract was assessed by trypan blue exclusion and MTT assay. Rates of oxygen consumption of isolated mitochondria were determined with a Clark oxygen electrode. RESULTS It was found that the hydromethanolic extract induced cell death of HepG2 cells in a dose-dependent fashion. The IC(50) of Phyllanthus urinaria extract measured by trypan blue exclusion and MTT assay were 431+/-65 microg/ml and 445+/-62 microg/ml, respectively. Morphological changes of the cells were also observed. With isolated rat liver mitochondria, the extract slightly stimulated mitochondrial state 4 respiration but profoundly depressed state 3 respiration and respiratory control ratio. CONCLUSIONS The extract impairs energy metabolism by acting as inhibitor of oxidative phosphorylation and weak mitochondrial uncoupler. These mitochondrial effects may play a role in the cytotoxic action of Phyllanthus urinaria extract on HepG2 cells. These results provide preliminary experimental evidence supporting the use of Phyllanthus urinaria against hepatocellular carcinoma and open the possibility of considering this plant an adjunctive medicine for the treatment of this deadly disease.

Comparison of the antioxidant and cytotoxic activities of Phyllanthus virgatus and Phyllanthus amarus extracts.

Objective: To determine the antioxidant activity and cytotoxicity of Phyllanthus virgatus crude extract compared to Phyllanthus amarus.Methods: Phenolic contents of the hydromethanolic extracts were measured using Folin-Ciocalteu reagent. Antioxidant activity was evaluated by the 2,2-diphenyl-1-picrylhydrazyl hydrate free radical scavenging and antilipid peroxidation assays. Cytotoxicity on human hepatoma HepG2 cells was assessed by trypan blue and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide viability assays. A stereomicroscope was used to observe and photograph the morphology of the cells. Oxygen consumption of the HepG2 cells was measured using a Clark oxygen electrode. Results: The extract of P. virgatus, which contained more phenolic compounds than P. amarus extract, had higher cytotoxicity and showed higher free radical scavenging activity and more inhibition of peroxidation in a linoleic acid system. P. virgatus extract conspicuously increased the oxygen consumption of HepG2 cells, while P. amarus extract had little stimulatory effect. Conclusion: The hydromethanolic extract of P. virgatus had stronger antioxidant and cytotoxic action than P. amarus extract. The stimulation of HepG2 cell respiration by P. virgatus extract suggests the extract alters mitochondrial function; this action could play a role in the cytotoxicity of this plant.

The Effects of Wild Ginger (Costus speciosus (Koen) Smith) Rhizome Extract and Diosgenin on Rat Uterine Contractions

The aim of this study was to investigate the effects of wild ginger (Costus speciosus (Koen) Smith, Costaceae) rhizome extract on uterine contractility. We particularly examined the effects on spontaneous phasic contractions and the mechanisms whereby it exerts its effects. Wild ginger rhizomes were ethanolic extracted and their constituents analyzed. Isometric force was measured in strips of longitudinal myometrium and the effects of the extract studied. The extract (10 mg/100 mL) increased spontaneous contractions. The amplitude and frequency of the phasic contraction were significantly increased along with basal tension. Force produced in the presence of the extract was abolished by inhibition of l-type calcium channels or myosin light chain kinase (MLCK). The actions of the extract were not blocked by the estrogen receptor blocker, fulvestrant. Although significant amounts of diosgenin were present in the extract, we found that, depending upon its concentration, diosgenin had either no effect or was inhibitory on force. Interestingly, the extract induced significant amounts of force in the absence of extracellular calcium, which could be blocked by inhibition of the sarcoplasmic reticulum calcium-ATPase (SERCA), but not fulvestrant. We conclude that wild ginger rhizome extract stimulates phasic activity in rat uterus. Our data suggest that the uterotonic effect is due to nonestrogenic effects and not those of diosgenin. Wild ginger was able to increase contraction via calcium entry on l-type calcium channels and sarcoplasmic reticulum (SR) calcium release. We suggest that wild ginger rhizome extract may be a useful uterine stimulant.

Participation of citral in the bronchodilatory effect of ginger oil and possible mechanism of action.

The extract of ginger, the rhizomes of Zingiber officinale Roscoe (Zingiberaceae), has been reported to possess anti-hyperactivity and anti-inflammation on airway. The present study described brochodilatory activity of ginger oil and identified its active compound. Ginger oil was extracted by hydro-distillation. The compositions of ginger oil were analyzed by gas chromatography and mass spectrometer. Citral, eucalyptol and camphene were found to be the major components. Ginger oil and citral, but not camphene, suppressed rat tracheal contraction induced by carbachol (CCh). Consistent with previous report, eucalyptol showed a relaxing effect on rat airway. Since the content of eucalyptol in ginger oil was relatively low, the contribution of eucalyptol to the bronchodilatory effect of ginger oil was small. To elucidate the mechanisms responsible for the myorelaxing effect, propranolol (a β-adrenergic receptor antagonist), indomethacin (a COX inhibitor) and L-NAME (a NOS inhibitor) were used to block the inhibitory effects of ginger oil and citral. It was found that propranolol, but not indomethacin and L-NAME, reversed bronchodilatory effects of both ginger oil and citral, suggesting that a possible mechanism involved β-adrenergic receptor. This study provides the pharmacological basis supporting the therapeutic potential of Z. officinale rhizomes as a bronchodilator.

Antioxidant, α-glucosidase inhibitory activity and sub-chronic toxicity of Derris reticulata extract: its antidiabetic potential

BackgroundAntidiabetic activity of Derris reticulata extract on alloxan-induced diabetic rats has been reported. The extract was found to lower blood glucose and inhibit intestinal glucose absorption. The aim of this study was to further investigate mechanisms underlying the antihyperglycemic activity of D. reticulata extract in vitro.MethodsThe aqueous extract was obtained from D. reticulata stem. Phytochemical screening, total phenolic, and flavanoid contents were examined. ABTS and DPPH scavenging assays, and FRAP method were used to determine in vitro antioxidant activities. Measurement of cell viability on alloxan-induced cellular damage was performed in the insulin-secreting RINm5F cells by MTT assay. The effects of the extract on α-glucosidase activity and insulin release were studied. In addition, sub-chronic toxicity test in rats was also conducted.ResultsThe results revealed that the extract, which consisted of terpenoids, saponins, tannins and flavonoids, possessed moderate radical scavenging activities. Pre-treatment of RINm5F cells with the extract was also found to exert moderate, but significant, in vitro protection against alloxan, an oxidative stress producing agent. Unlike glibenclamide, the extract did not stimulate insulin secretion. However, the extract was found to inhibit α-glucosidase activity similar to acarbose. It was found that in sub-chronic toxicity studies D. reticulata extract did not cause mortality or produce any remarkable haematological, biochemical and histopathological adverse effects in rats.ConclusionsThe data suggest that the possible mechanisms underlying antihyperglycemic activity of D. reticulata extract are cytoprotective effect on pancreatic cells, presumably by its antioxidant activity, and inhibition of α-glucosidase. Sub-chronic toxicity study also provides scientific evidence to corroborate the safety of this plant as an alternative antidiabetic agent.

Synthesis, interfacial properties, and antimicrobial activity of a new cationic gemini surfactant

Tetramethylene-1,4-bis(N,N-dodecylammonium bromide), cationic gemini surfactant, (12-4-12) was first synthesized with an one-step and shortened procedure and its interfacial and antimicrobial properties were compared with a conventional single-chain cationic surfactant, cetyltrimethylammonium bromide (CTAB). The interfacial and thermodynamic properties of both surfactants reveal that critical micelle concentration (CMC) of this novel synthetic cationic dimeric surfactant is lower than that of cationic monomeric surfactant at almost 15 times of its magnitude, which is due to the increase in hydrophobicity of the surfactant molecules by having dual hydrocarbon chains. In comparison with CTAB, the produced compound 12-4-12 yields much better interfacial and thermodynamic properties. The antimicrobial activities of the synthesized gemini surfactant were tested against eight strains of bacteria, as well as two strains of fungi. The results showed that both 12-4-12 compound and CTAB exhibited higher inhibitory effects on the growth of Gram-positive bacteria and fungi than that of Gram-negative bacteria. The minimum inhibitory concentrations in molar of 12-4-12 against all tested Gram-negative bacteria were lower than those of CTAB, which is hypothetically due to the lower HLB together with smaller CMC values of our gemini surfactant.