Sukyung Kim

In vitro activity of (-)-deoxypergularinine, on its own and in combination with anti-tubercular drugs, against resistant strains of Mycobacterium tuberculosis.

BACKGROUND The increasing incidence of multidrug-resistant tuberculosis (MDR-TB) infections has created a need for new effective drugs that also target extensively drug-resistant tuberculosis (XDR-TB) and/or augment the activities of existing drugs against tuberculosis. AIM This study searched natural products for a new lead compound that targets MDR/XDR-TB. METHODS An active compound was purified from the roots of Cynanchum atratum Bunge (Asclepiadaceae) after screening 1640 plant extracts, and its inhibitory effects against MDR/XDR strains and synergistic effects with existing anti-TB drugs were assessed using the resazurin, MGIT, and checkboard assays. RESULTS (-)-Deoxypergularinine, purified from the roots of C. atratum, inhibited not only M. tuberculosis but also MDR/XDR strains. The minimum inhibitory concentrations (MICs) of (-)-deoxypergularinine for H37Ra, H37Rv, MDR, and XDR strains were all about 12.5 µg/ml. Moreover, combinations of (-)-deoxypergularinine with the first-line standard drugs rifampicin or isoniazid afforded six- and eight-fold reductions in drug MIC values, respectively, against strain H37Ra. CONCLUSIONS (-)-Deoxypergularinine exerts anti-tubercular activities not only against normal tuberculosis strains but also MDR/XDR strains, and synergic effects with rifampicin and isoniazid for the H37Ra strain. The alkaloid may be valuable for targeting M/XDR M. tuberculosis.

Acute, subchronic oral toxicity, toxicokinetics, and genotoxicity studies of DFC-2, an antitubercular drug candidate

ABSTRACT The infectious disease tuberculosis remains a serious global health issue and is responsible for nearly 1.8 million deaths every year. In our previous study, DFC‐2 was confirmed to show anti‐tubercular activity against drug‐susceptible and drug‐resistant strains of Mycobacterium tuberculosis. To support the safety‐in‐use of DFC‐2 as an anti‐tubercular drug, DFC‐2 was tested via single‐ and 28‐day repeated‐dose oral toxicity study and mutagenicity assays. In the oral toxicity study, a single oral dose of DFC‐2 at 2000 mg/kg did not produce deaths or abnormal lesions in the internal organs of rats. The results of a 28‐day orally repeated dose of DFC‐2 did not show treatment‐related deaths or obvious toxicity symptoms in the animals treated with a dose of 300 mg/kg/day during the experimental period. Therefore, the no‐observed‐adverse‐effect level (NOAEL) of DFC‐2 was determined as 300 mg/kg/day for both male and female rats. In addition, DFC‐2 showed no genetic toxicity in in vitro bacterial reverse mutation test, in vitro chromosomal aberration test, and in vivo mouse bone marrow micronucleus formation test. These results indicate that DFC‐2 is a promising anti‐tubercular drug candidate with a favorable safety profile. HighlightsOral toxicity (acute, subchronic) and genotoxicity of a new antitubercular drug candidate, DFC‐2, was investigated in rats.No acute oral toxicity or adverse effects were observed at dosages up to 2000 mg/kg body weight.NOAEL (No observed adverse effect level) for subchronic toxicity (28 days) in rats is 300 mg/kg/day.Negative outcomes obtained in the genotoxicity tests.

Naphthofuroquinone derivatives show strong antimycobacterial activities against drug-resistant Mycobacteria

Tuberculosis, one of the world’s major health problems, has become more serious due to the emergence of multi-drug resistant (MDR) and extensively drug-resistant (XDR) Mycobacterium tuberculosis (MTB). In this study, we performed three anti-MTB assays to evaluate the anti-mycobacterial activity of naphthofuroquinone derivatives against drug-resistant MTB. Among them, methyl 5-[2-(dimethylamino)ethoxy]-7,12-dioxo-7,12-dihydrodinaphtho[1,2-b:2′,3′-d]furan-6-carboxylate (DFC2) exhibited strong anti-mycobacterial activity against MTB H37Ra, H37Rv and four drug-resistant MTB strains. The MIC of DFC2 ranged from 0.19–0.39 μg/ml to 0.78–1.56 μg/ml against all tested MTB strains. Moreover, DFC2 showed low cytotoxicity against fibroblast cells (L929) at concentrations 10–40-fold higher than their MICs. The IC50 value of DFC2 against L929 cells was 15.218 μg/ml. In addition, DFC2 reduced the number of intracellular M. tuberculosis in macrophages in a dose-dependent manner. Taken together, our results indicate DFC2 to be promising new candidate agents for the treatment of tuberculosis.

In vitro activity of collinin isolated from the leaves of Zanthoxylum schinifolium against multidrug- and extensively drug-resistant Mycobacterium tuberculosis

BACKGROUND Tuberculosis is a very serious infectious disease that threatens humanity, and the emergence of multidrug-resistant (MDR), extensively drug-resistant (XDR) strains resistant to drugs suggests that new drug development is urgent. In order to develop new tuberculosis drug, we have conducted in vitro anti-tubercular tests on thousands of plant-derived substances and finally found collinin extracted from the leaves of Zanthoxylum schinifolium, which has an excellent anti-tuberculosis effect. PURPOSE To isolate an anti-tubercular bioactive compound from the leaves of Z. schinifolium and evaluate whether this agent demonstrates any potential in vitro characteristics suitable for the development of future anti-tubercular drugs to treat MDR and XDR Mycobacterium tuberculosis. METHODS The methanolic extracts of the leaves of Z. schinifolium were subjected to bioassay-guided fractionation against M. tuberculosis using a microbial cell viability assay. In addition, following cell cytotoxicity assay, an intracellular anti-mycobacterial activity of the most active anti-tubercular compound was investigated after it was purified. RESULTS The active compound with anti-tubercular activity isolated from leaves of Z. schinifolium was identified as a collinin. The extracted collinin showed anti-tubercular activity against both drug-susceptible and -resistant strains of M. tuberculosis at 50% minimum inhibitory concentrations (MIC50s) of 3.13-6.25 µg/ml in culture broth and MIC50s of 6.25-12.50 µg/ml inside Raw264.7 and A549 cells. Collinin had no cytotoxicity against human lung pneumocytes up to a concentration of 100 µg/ml (selectivity index > 16-32). CONCLUSIONS Collinin extracted from the leaves of Z. schinifolium significantly inhibits the growth of MDR and XDR M. tuberculosis in the culture broth. In addition, it also inhibits the growth of intracellular drug-susceptible and drug-resistant tuberculosis in Raw264.7 and A549 cells. To our knowledge, this is the first report on the in vitro anti-tubercular activity of collinin, and our data suggest collinin as a potential drug to treat drug-resistant tuberculosis. Further studies are warranted to assess the in vivo efficacy and therapeutic potential of collinin.

In vitro Antitubercular Activity of 3‐Deoxysappanchalcone Isolated From the Heartwood of Caesalpinia sappan Linn.

Responsible for nearly 1.5 million deaths every year, the infectious disease tuberculosis remains one of the most serious challenges to global health. The emergence of multidrug‐resistant tuberculosis and, more recently, extensively drug‐resistant tuberculosis poses a significant threat in our effort to control this epidemic. New drugs are urgently needed to combat the growing threat of antimicrobial resistance. To achieve this goal, we screened approximately 500 species of medicinal plant methanol extracts and their solvent partitioned fractions for potential inhibitors of Mycobacterium tuberculosis growth. Using microdilution screening, the ethyl acetate solvent partitioned fraction from the heartwood of Caesalpinia sappan exhibited strong antitubercular activity. We isolated the active compound and identified it as 3‐deoxysappanchalcone. The extracted 3‐deoxysappanchalcone possessed activity against both drug‐susceptible and drug‐resistant strains of M. tuberculosis at MIC50s of 3.125–12.5 μg/mL in culture broth and MIC50s of 6.25–12.5 μg/mL inside macrophages and pneumocytes. 3‐Deoxysappanchalcone was also found to act in partial synergy with streptomycin/ethambutol against M. tuberculosis H37Rv. 3‐Deoxysappanchalcone had no cytotoxicity against the A549 cell line up to a concentration of 100 μg/mL (selectivity index > 8–32). Further studies are warranted to establish the in vivo effect and therapeutic potential of 3‐deoxysappanchalcone. Copyright