Anti-fungal and anti-bacterial activities of ethanol extracts of selected traditional Chinese medicinal herbs

Objective:To evaluate in ritro antimicrobial activities of selected 58 ethno-medicinal plant extracts with a view to assess their therapeutic potential.Methods:A total of 58 traditional Chinese medicinal plants were carefully selected based on the literature review and their traditional use.The antimicrobial activities of ethanol extracts of these medicinal plants were tested against fungi(Aspergillus funigaius),yeast(Candida albicans),gram-negative(Acirelobacter haumannii and Pseudornnruis aeruginosa)and gram-positive bacteria(Staphglococcus aureus).The activities were tested at three different concentrations of 1.00,0.10 and 0.01 mg/mL.The data was analysed using Gene data Screener program.Results:The measured antimicrobial activities indicated that out of the 58 plant extracts,15 extracts showed anti-fungal activity and 23 extracts exhibited anti-bacterial activity.Eight plant extracts have exhibited both anti-bacterial and anti-fungal activities.For instance,Eucommia ulmoides,Pohgonum cuspidcrtum,Poria cocas and Uncaria rhineophylla showed activity against both bacterial and fungal strains,indicating their broad spectrum of activity.Conclusions:The results revealed that the ethanol extracts of 30 plants out of the selected 58 possess significant antimicrobial activities.It is interesting to note that the findings from the current study are consistent with the traditional use.A clear correlation has also been found between the antimicrobial activity and the flavonoid content of the plant extracts which is in agreement with the literature.Hence.the results presented here can be used to guide the selection of potential plant species for the isolation and structure elucidation of novel antimicrobial compounds in order to establish the structure-activity relationship.This in turn is expected to lead the way to the discovery of novel antimicrobial agents for therapeutic use.

Evaluation of the effect of compound aqueous solubility in cytochrome P450 inhibition assays

It is a common practice in drug discovery organizations to screen new chemical entities in order to predict future drug-drug interactions. For this purpose, there are two main assay strategies, one based on recombinant cytochrome P450 (rCYP) enzymes and fluorescent detection, and other on human liver microsomes (HLM) and liquid chromatography coupled to mass spectrometry. Many authors have reported a poor correlation between both technologies, giving rise to concerns about the usefulness of fluorometric methods for predicting drug-drug interactions. In this study, we investigated the role that compound aqueous kinetic solubility may play in this lack of correlation. We found that drug discovery compounds with unacceptable kinetic solubility, measured by a turbidimetric solutibility assay, tended to yield higher IC50 values in in vitro models based on human liver microsomes, whereas compounds with kinetic solubility values higher than 50 μM showed very similar IC50 values in both in vitro models. Our results show that the turbidimetric solubility assay is a useful tool to identify those discovery compounds that may require further investigation in order to avoid overlooking future drug-drug interactions.

HCS strategy targeting dysregulation of the VHL/HIF pathway for drug discovery

One-third of top-selling drugs are derived from natural products. When only a fraction of the bioactive natural products diversity has been explored, huge opportunities still remain for discovering novel leads for the development of new drugs. Clear cell renal cell carcinoma (ccRCC) is a highly vascular tumour arising from epithelial elements. Mutations in the Von Hippel-Lindau (VHL) gene are responsible for VHL disease and arise in the majority of Renal Cell Carcinoma (RCC) as well as in other types of cancer. Renal carcinoma cell lines with naturally occurring VHL mutations (RCC4 VA) and their genetically matched wild-type VHL (RCC4 VHL) counterparts were seeded onto 96-well plates and allowed to attach overnight. Fungal extracts were tested on both cell lines. Clinically useful antitumor agents were used as positive controls and as reference points to establish the efficacy and selectivity of the new compounds. Renal cell carcinoma cell lines expressing VHL or not were treated with Carboxyfluorescein succinimidyl ester (CFSE). The day after cell inoculation, extracts were added and during the following days of incubation, fluorescence intensity was measured as a surrogate marker for cell viability. The most promising extracts selectively inhibited growth of pVHL-defi- cient cells but not of wild-type VHL cells. We used High Content Bio-imaging, a complete cellular imaging workflow that integrates instruments and software to acquire and analyze images, to evaluate their effect. Cell imaging can reveal effects that would be overlooked by other cell assay approaches. This target-based whole cell screen is a new strategy, which ensures cell permeability and target selectivity especially in natural product screening where natural product purification is a labour of extensive work. This approach permitted a dynamic study where fluorescence was measured without affecting cell viability and enabling a better detection of cytotoxic effects such as autophagy, senescence or late apoptosis.

Discovery of gargantulides B and C,new 52-membered macrolactones from Amycolatopsis sp.Complete absolute stereochemistry of the gargantulide family

Gargantulides B and C,two new and highly complex 52-membered glycosylated macrolactones,were isolated from Amycolatopsis sp.strain CA-230715 during an antibacterial screening campaign.The structures of these giant macrolides were elucidated by 2D NMR spectroscopy and shown to be related to gargantulide A,although containing additional β-glucopyranose and/orα-arabinofuranose monosaccharides separately attached to their backbones.Genome sequencing allowed the identification of a strikingly large 216 kbp biosynthetic gene cluster,among the largest type Ⅰ PKS clusters described so far,and the proposal of a previously unreported biosynthetic pathway for gargantulides A-C.The absolute configurations of gargantulides B and C were assigned based on a combination of NMR and bioinformatics analysis of ketoreductase and enoylreductase domains within the multimodular type Ⅰ PKS.In addition,the absolute stereochemistry of gargantulide A has now been revised and completed.Gargantulides B and C display potent antibacterial activity against a set of drug-resistant Gram-positive bacteria and moderate activity against the clinically relevant Gram-negative pathogen Acinetobacter baumannii.