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.

Bacopa monnieri (L.) Wettst. was studied for shoot induction and regeneration on Murashige and Skoog (MS) medium supplemented with different plant growth regulators. Stem explants cultured on medium containing 0.1 mg/l thidiazuron (TDZ) resulted in the highest number of shoots (117 shoots/explant). Regenerated plants from medium with 0.5 mg/l TDZ contained the highest level of pseudojujubogenin glycosides [(30.62 d 1.29) mg/g dry wt] which was 2-fold higher than that of in vitro grown plants of the same age [(16.96 d 1.49) mg/g dry wt]. Plantlets regenerated from 0.1 mg/l TDZ also showed a high level of pseudojujubogenin glycosides [(27.94 d 1.19) mg/g dry wt]. The effect of elicitor on pseudojujubogenin glycosides accumulation in B. monnieri whole plant cultures was investigated. Chitosan at 150 mg/l and yeast extract at 2 mg/ml increased the pseudojujubogenin glycosides production [(40.83 d 2.24) mg/g dry wt and (40.05 d 2.37) mg/g dry wt, respectively] after 7 days, which was 6-fold higher than in the control cultures.

The current study was aimed to investigate pancreatic protective and anti-diabetic activities of the aqueous extract of Derris reticulata stem. First, we evaluated a cytoprotective potential of D. reticulata extract on alloxan-induced damage in vitro. Treatment with D. reticulata extract at the doses of 250 and 500 μg/ml significantly increased cell viability of the pancreatic β-cell line RINm5F after exposure of alloxan. The anti-hyperglycemic activity of D. reticulata extract was further studied in alloxan-induced diabetic rats. A significant reduction in blood glucose level along with an increase in body weight was observed in diabetic rats treated with D. reticulata extract at 250 mg/kg body weight for 15 days. Serum aspartate transaminase and alanine transaminase levels were also significantly decreased compared to diabetic control rats. In accordance with in vitro cytoprotective effect, histopathological examination revealed that pancreatic islet cells of the extract-treated diabetic rat were less damage than those of the untreated diabetic group. In order to find another possible mechanism of action underling hypoglycemic activity, the effect on glucose absorption was examined using everted sac jejunum. The results showed that D. reticulata extract suppressed glucose absorption from small intestine. To corroborate safety use of D. reticulata extract, acute oral toxicity was also conducted in rats. Our results showed that none of the tested doses (250, 500, 1,000, and 2,000 mg/kg) induced signs of toxicity or mortality after administration of the extract. The results suggested that D. reticulata extract possess anti-diabetic activity, which resulting from its pancreatic cytoprotective effect and inhibition of intestinal glucose absorption.

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