Anticancer activity, apoptosis and a structure-activity analysis of a series of 1,4-naphthoquinone-2,3-bis-sulfides.

We have previously reported on the synthesis of 1,4-naphthoquinone-sulfides and in this investigation we report on their anticancer activity against 6 human cancer cell lines to evaluate their cytostatic effects. The 1,4-naphthoquinone-2,3-bis-sulfides were most effective against melanoma (UACC62) (GI50 = 6.5-10 µM) and prostate (PC3) (GI50 = 5.51-8.53 µM) cancer cell lines. They exhibited better cytostatic effects than etoposide (GI50 = 0.56-36.62 µM), parthenolide (GI50 = 3.58-25.97 µM) and VK3 (GI50 = 3.41-22.59 µM) against several of the cancer cell lines. These compounds are generally more selective for cancer cells than for normal human lung fetal fibroblasts (WI-38). One compound produces ROS which results in breast (MCF7) cancer cell death caused by apoptosis as evidenced by caspase 3/7 activation. Apoptosis was found to occur by a mitochondrial pathway and not by cell cycle arrest. Gene expression studies showed that p53 (a tumour suppressor), Mdm-2 (a p53 regulator) and Bcl-2 (apoptosis inhibitor) were up-regulated during apoptosis induction. These results encourage further research for potential application in cancer chemotherapy.

Anticancer activities of vitamin K3 analogues.

In a previous study we reported on the synthesis of 1,4-naphthoquinone-sulfides by thiolation of 1,4-naphthohydroquinones with primary aryl and alkyl thiols using laccase as catalyst. These compounds were synthesized as Vitamin K3 analogues. Vitamin K3 (VK3; 2-methyl-1,4-naphthoquinone; menadione) is known to have potent anticancer activity. This investigation reports on the anticancer activity of these VK3 analogues against TK10 renal, UACC62 melanoma, MCF7 breast, HeLa cervical, PC3 prostate and HepG2 liver cancer cell lines to evaluate their cytostatic effects. A 1,4-naphthohydroquinone derivative exhibited potent cytostatic effects (GI50 = 1.66-6.75 µM) which were better than that of etoposide and parthenolide against several of the cancer cell lines. This compound produces reactive oxygen species and disrupts the mitochondrial membrane potential in the MCF7 breast cancer cell line which is an indication that the cells undergo apoptosis. The 1,4-naphthoquinone sulfides also had potent cytostatic effects (GI50 = 2.82-9.79 µM) which were also better than that of etoposide, parthenolide and VK3 against several of the cancer cell lines. These compounds are generally more selective for cancer cells than for normal human lung fetal fibroblasts (WI-38). They also have moderate to weak cytostatic effects compared to etoposide, parthenolide and VK3 which have potent cytostatic effects against WI-38. One analogue induces apoptosis by activating caspases without arresting the cell cycle in the MCF7 breast cancer cell line. These results inspire further research for possible application in cancer chemotherapy.

Investigation of the antimicrobial and anticancer activity of aminonaphthoquinones.

In this study, we report on the inhibitory activity of synthesized aminonaphthoquinones against two bacterial and one fungal species to determine their antimicrobial properties. A minimum inhibitory concentration (MIC) of 7.8 µg/mL was obtained against the fungus, Candida albicans, which was better than that of Amphotericin B (MIC = 31.25 µg/mL). Escherichia coli (Gram -), was inhibited at a MIC of 23.4 µg/mL and Staphylococcus aureus (Gram +) at a MIC of 31.3 µg/mL. The aminonaphthoquinones were also screened against HCT116 colon, PC3 prostate and HepG2 liver cancer cell lines to evaluate their cytostatic effects. They had potent activity (GI50 = 5.87-9.90 µM) which was about three-6-fold better than that of parthenolide (GI50 = 25.97 µM) against the prostate cancer cell line. These compounds were generally more selective for cancer cells than for normal human lung fetal fibroblasts (WI-38).

A one-pot laccase-catalysed synthesis of coumestan derivatives and their anticancer activity.

Suberase®, a commercial laccase from Novozymes, was used to catalyse the synthesis of coumestans. The yields, in some cases, were similar to or better than that obtained by other enzymatic, chemical or electrochemical syntheses. The compounds were screened against renal TK10, melanoma UACC62 and breast MCF7 cancer cell-lines and the GI50, TGI and LC50 values determined. Anticancer screening showed that the cytostatic effects of the coumestans were most effective against the melanoma UACC62 and breast MCF7 cancer cell-lines exhibiting potent activities, GI50=5.35 and 7.96µM respectively. Moderate activity was obtained against the renal TK10 cancer cell-line. The total growth inhibition, based on the TGI values, of several of the compounds was better than that of etoposide against the melanoma UACC62 and the breast MCF7 cancer cell lines. Several compounds, based on the LC50 values, were also more lethal than etoposide against the same cancer cell lines. The SAR for the coumestans is similar against the melanoma UACC62 and breast MCF7 cell lines. The compound having potent activity against both breast MCF7 and melanoma UACC62 cell lines has a methyl group on the benzene ring (ring A) as well as on the catechol ring (ring B). Anticancer activity decreases when methoxy and halogen substituents are inserted on rings A and B.

One-pot laccase-catalysed synthesis of 5,6-dihydroxylated benzo[b]furans and catechol derivatives, and their anticancer activity.

A commercial laccase, Suberase® from Novozymes, was used to catalyse the synthesis of 5,6-dihydroxylated benzo[b]furans and catechol derivatives. The yields were, in some cases, similar to or better than that obtained by other enzymatic, chemical or electrochemical syntheses. The synthesised derivatives were screened against renal (TK10), melanoma (UACC62), breast (MCF7) and cervical (HeLa) cancer cell lines. GI50, TGI and LC50 are reported for the first time. Anticancer screening showed that the cytostatic effects of the 5,6-dihydroxylated benzo[b]furans were most effective against the melanoma (UACC62) cancer cell line with several compounds exhibiting potent growth inhibitory activities (GI50=0.77-9.76 µM), of which two compounds had better activity than the anticancer agent etoposide (GI50 0.89 µM). One compound exhibited potent activity (GI50=9.73 µM) against the renal (TK10) cancer cell line and two exhibited potent activity (GI50=8.79 and 9.30 µM) against the breast (MCF7) cancer cell line. These results encourage further studies of the 5,6-dihydroxylated benzo[b]furans for their potential application in anticancer therapy.

Antimalarial and anticancer activities of artemisinin-quinoline hybrid-dimers and pharmacokinetic properties in mice.

Malaria, one of the three most important life-threatening infectious diseases, is recommended to be treated with ACT (artemisinin combination therapy) against which Plasmodium falciparum already displayed resistance. Two artemisinin-4-amino-quinoline hybrid-dimers (1 and 2), previously synthesized, possessed low nanomolar in vitro antiplasmodial activity, while poorly toxic against mammalian cells. They are here investigated to ascertain whether this antimalarial activity would be carried on in vivo against Plasmodium vinckei. During the four day treatment, parasitemia of less than 1% were observed on day 5 after doses from 2.5 mg/kg ip and 50 mg/kg po for hybrid-dimer 1, and from 7.5 mg/kg ip and 25 mg/kg po for hybrid-dimer 2. Snapshot pharmacokinetic analysis demonstrated that the antiplasmodial activity of these C-10-acetal artemisinin dimers may be due to active metabolites, which were confirmed by in silico findings. Hybrid-dimer 1 also displayed potent in vitro activity against tumor cells and was found to be more active than etoposide against TK10, UACC62 and MCF7 cell lines (TGI values 3.45 vs. 43.33 µM, 2.21 vs. 45.52 µM and 2.99 vs. >100 µM, respectively). The 1,3-diaminopropane linker, present in hybrid-dimer 1, was therefore identified as the optimum linker.

A laccase-catalysed one-pot synthesis of aminonaphthoquinones and their anticancer activity.

Nuclear monoamination of a 1,4-naphthohydroquinone with primary aromatic amines was catalysed by the commercial laccase, Novozym 51003, from Novozymes to afford aminonaphthoquinones. The synthesis was accomplished by reacting a mixture of the primary amine and 1,4-naphthohydroquinone in succinate-lactate buffer and a co-solvent, dimethylformamide, under mild reaction conditions in a vessel open to air at pH 4.5 and pH 6.0. Anticancer screening showed that the aminonaphthoquinones exhibited potent cytostatic effects particularly against the UACC62 (melanoma) cancer cell line (GI(50)=3.98-7.54 µM). One compound exhibited potent cytostatic effects against both the TK10 (renal) and the UACC62 (melanoma) cancer cell line. The cytostatic effects of this compound (GI(50)=8.38 µM) against the TK10 cell line was almost as good as that of the anticancer agent, etoposide (GI(50)=7.19µM). Two compounds exhibited potent cytostatic effects against both the UACC62 (melanoma) and the MCF7 (breast) cancer cell lines. The total growth inhibition (TGI) of most of the compounds was better than that of etoposide against the UACC62 cell line. Three compounds (TGI=7.17-7.94 µM) exhibited potent cytostatic effects against the UACC62 cell line which was 7 to 8-fold better than that of etoposide (TGI=52.71 µM). The results are encouraging for further study of the aminonaphthoquinones for potential application in anticancer therapy.