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Wong I.L.K.,Hong Kong Polytechnic University | Wong I.L.K.,State Key Laboratory in Chinese Medicine and Molecular Pharmacology | Chan K.-F.,Hong Kong Polytechnic University | Chan K.-F.,State Key Laboratory in Chinese Medicine and Molecular Pharmacology | And 7 more authors.
Antimicrobial Agents and Chemotherapy | Year: 2014

Treatment of leishmaniasis by chemotherapy remains a challenge because of limited efficacy, toxic side effects, and drug resistance. We previously reported that synthetic flavonoid dimers have potent antipromastigote and antiamastigote activity against Leishmania donovani, the causative agent of visceral leishmaniasis. Here, we further investigate their leishmanicidal activities against cutaneous Leishmania species. One of the flavonoid dimers (compound 39) has marked antipromastigote (50% inhibitory concentrations [IC50s], 0.19 to 0.69 μM) and antiamastigote (IC50s, 0.17 to 2.2 μM) activities toward different species of Leishmania that cause cutaneous leishmaniasis, including Leishmania amazonensis, Leishmania braziliensis, Leishmania tropica, and Leishmania major. Compound 39 is not toxic to peritoneal elicited macrophages, with IC50 values higher than 88 μM. In the mouse model of cutaneous leishmaniasis induced by subcutaneous inoculation of L. amazonensis in mouse footpads, intralesional administration of 2.5 mg/kg of body weight of compound 39.HCl can reduce footpad thickness by 36%, compared with that of controls values. The amastigote load in the lesions was reduced 20-fold. The present study suggests that flavonoid dimer 39 represents a new class of safe and effective leishmanicidal agent against visceral and cutaneous leishmaniasis. © 2014, American Society for Microbiology.


Wong I.L.K.,Hong Kong Polytechnic University | Wong I.L.K.,State Key Laboratory in Chinese Medicine and Molecular Pharmacology | Chan K.-F.,Hong Kong Polytechnic University | Chan K.-F.,State Key Laboratory in Chinese Medicine and Molecular Pharmacology | And 5 more authors.
Journal of Medicinal Chemistry | Year: 2012

The present study found that synthetic flavonoid dimers with either polyethylene glycol linker or amino ethyleneglycol linker have marked leishmanicidal activity. Compound 39 showed very consistent and promising leishmanicidal activity for both extracellular promastigotes (IC50 ranging from 0.13 to 0.21 μM) and intracellular amastigotes (IC50 = 0.63 μM) irrespective of the drug-sensitivity of parasites. Moreover, compound 39 displayed no toxicity toward macrophage RAW 264.7 cells (IC 50 > 100 μM) and primary mouse peritoneal elicited macrophages (IC50 > 88 μM). Its high value of therapeutic index (>140) was better than other highly potent antileishmanials such as amphotericin B (therapeutic index = 119). Compound 39 is therefore a new, safe, and effective antileishmanial candidate compound which is even effective against drug-refractory parasites. © 2012 American Chemical Society.


Bin J.W.,Ocean University of China | Wong I.L.K.,Hong Kong Polytechnic University | Wong I.L.K.,State Key Laboratory in Chinese Medicine and Molecular Pharmacology | Hu X.,Hong Kong Polytechnic University | And 7 more authors.
Journal of Medicinal Chemistry | Year: 2013

A novel series of permethyl ningalin B analogues were synthesized and evaluated for their P-glycoprotein (P-gp)-modulating activities in a P-gp-overexpressing breast cancer cell line (LCC6MDR). Compounds 35 and 37, which possess one methoxy group and one benzyloxy group at aryl ring C, displayed the most potent P-gp-modulating activity. A 1 μM concentration of 35 and 37 resensitized LCC6MDR cells toward paclitaxel by 42.7-fold, with respective EC50 values of 93.5 and 110.0 nM. Their mechanism of P-gp modulation is associated with an increase in intracellular drug accumulation. Their advantages also include low cytotoxicity (IC50 for L929 fibroblast >100 μM) and high therapeutic indexes (>909 after normalization with their EC50 values). 35 is not a substrate of P-gp. They are potentially dual-selective modulators for both P-gp and breast cancer resistance protein transporters. The present study demonstrates that these new compounds can be employed as effective and safe modulators of P-gp-mediated drug resistance in cancer cells. © 2013 American Chemical Society.


Yuan J.,Ocean University of China | Wong I.L.K.,Hong Kong Polytechnic University | Wong I.L.K.,State Key Laboratory in Chinese Medicine and Molecular Pharmacology | Jiang T.,Ocean University of China | And 6 more authors.
European Journal of Medicinal Chemistry | Year: 2012

Three methylated quercetins and a series of O-3 substituted 5,7,3′,4′-tetra-O-methylated quercetin derivatives have been synthesized and evaluated on the modulating activity of P-gp, BCRP and MRP1 in cancer cell lines. Compound 17 (with a 2-((4-methoxybenzoyl)oxy)ethyl at O-3) is the most potent P-gp modulator. Three derivatives, compound 9 (3,7,3′,4′-tetra-O-methylated quercetin), compound 14 (with a 2-((3-oxo-3-(3,4,5trimethoxyphenyl)prop-1-en-1-yl)oxy)ethyl at O-3) and compound 17, consistently exhibited promising BCRP-modulating activity. Interestingly, compound 17 was found to be equipotent against both P-gp and BCRP. Importantly, these synthetic quercetin derivatives did not exhibit any inherent cytotoxicity to cancer cell lines or normal mouse fibroblast cell lines. These quercetin derivatives can be employed as safe and effective modulators of P-gp- or BCRP-mediated drug resistance in cancer. © 2012 Elsevier Masson SAS. All rights reserved.


Zhang P.Y.,Ocean University of China | Wong I.L.K.,Hong Kong Polytechnic University | Wong I.L.K.,State Key Laboratory in Chinese Medicine and Molecular Pharmacology | Yan C.S.W.,Hong Kong Polytechnic University | And 6 more authors.
Journal of Medicinal Chemistry | Year: 2010

A series of novel N-arylalkyl-3,4-diaryl-substituted pyrrole-2,5-diones were synthesized. They exhibited promising P-gp modulating activity in a P-gp overexpressing breast cancer cell line (LCC6MDR). Compound 6 (with three methoxy groups at D-ring) displayed the highest P-gp modulating activity. 6 at 1 μM can sensitize LCC6MDR cells toward paclitaxel by 18.2-fold. Interestingly, a synergy on modulating P-gp was noted when 6 and 25 were used together (fractional inhibitory concentration index FICI = 0.42). Combination of 6 (0.5 μM) and 25 (0.5 μM) resulted in a 66-fold sensitization of LCC6MDR cells toward paclitaxel. They also reversed P-gp mediated doxorubicin (DOX) and vincristine resistance. Kinetic characterization suggests that permethyl ningalin B analogues likely act as a noncompetitive inhibitor of P-gp-mediated DOX transport (Ki = 5.4-5.8 μM). The present study demonstrates that synthetic analogues of permethyl ningalin B can be employed as effective and safe modulators of P-gp-mediated drug resistance in cancer cells. © 2010 American Chemical Society.

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