Dudu Demir

New saccharin derivatives as tyrosinase inhibitors

A newly series of 6-(phenylurenyl/thiourenyl) saccharin (6a-y) derivatives were synthesized and their inhibitory effects on the diphenolase activity of banana tyrosinase were evaluated. A 70-fold purification of the enzyme with 6.85% yield was achieved by using a Sepharose 4B-l-tyrosine-p-amino benzoic acid affinity column. The result showed that all the synthesized compounds inhibited the tyrosinase enzyme activity. Among the compounds synthesized, 6-(3-iodophenylthiourenyl) saccharin (6s) was found to be most active one (K(i)=3.95 μM) and the inhibition kinetics analyzed by Lineweaver-Burk double reciprocal plots revealed that compound 6s was a competitive inhibitor. Structure-activity relationships study showed that generally, most of the 6-(phenylthiourenyl) saccharin derivatives (6m-y) exhibited higher inhibitory activity than 6-(phenylurenyl) saccharin derivatives (6a-l). An electron-withdrawing group at 3-position of phenylurenyl-ring increased in activity and the halogen series at 3-position of phenylthiourenyl-ring showed a qualitative relationship for higher inhibitory activity with increasing size and polarizability. We also calculated HOMO-LUMO energy levels and dipole moments of some selected the synthesized compounds (6a, 6h, 6m and 6s) using Gaussian software.

Synthesis and carbonic anhydrase inhibitory properties of novel coumarin derivatives

A newly series of water-soluble 1-alkyl-3-(4-methyl-7, 8-dihydroxy-2H-chromen-2-one) benzimidazolium chloride salts (3a-j) were synthesized and their inhibitory effects on the activity of purified human carbonic anhydrase (hCA) I and II were evaluated. hCA I and II from human erythrocytes were purified by a simple one step procedure by using Sepharose 4B-L-tyrosine-sulphanilamide affinity column. The result showed that all the synthesized compounds were inhibited the CA isoenzymes activity. Among them, 3g and 3j were found to be most active (IC50 = 22.09 µM and 20.33 µM) for hCA I and hCA II, respectively.

In vitro effects of some anabolic compounds on erythrocyte carbonic anhydrase I and II

The in vitro effects of the anabolic compounds, zeranol, 17 β-estradiol, diethylstilbestrol (DES), and trenbolone, on the activity of purified human carbonic anhydrase I and II were evaluated. In vitro CA enzyme activity was determined colorimetrically using the CO2 hydration method of Maren. IC50 values of the compounds that caused inhibition were determined by means of activity percentage diagrams. The IC50 concentrations of zeranol, 17 β-estradiol, DES and trenbolone on hCA I were 94, 55, 10, 898 µM and for hCA II 89, 159, 439 and 101 μM, respectively.

Purification and characterization of prophenoloxidase from Galleria mellonella L.

Abstract Prophenoloxidase (PPO) was purified from Galleria mellonella L. A 67-fold purification of the proenzyme with 352% yield was achieved by using a Sepharose 4B-L-tyrosine-p-amino benzoic acid affinity column. The purified enzyme was migrated as a single band on SDS-polyacrylamide gel electrophoresis. Km and Vmax values were 0.017 M and 1430.45 EU for catechol. Inhibition of PPO was investigated with inhibitors such as p-aminobenzoic acid, etyleneglycol, and ascorbic acid. Among them, ascorbic acid showed the strongest inhibitory activity with IC50 value of 2.94 μM. The current paper represents new strategies for the biological control of the Galleria mellonella L. insect.

Synthesis and carbonic anhydrase inhibitory properties of novel 1,4-dihydropyrimidinone substituted diarylureas

Abstract A new series of 1,4-dihydropyrimidinone (DHPM) substituted diaryl urea and thiourea derivatives were synthesized and their inhibitory effects on the activity of purified human carbonic anhydrase (hCA) I and II were evaluated. 4-Nitrophenyl-1,4-DHPM was prepared with dimedone, nitrobenzaldehyde and urea or thiourea and nitro group was reduced to amine derivative. The compound was reacted with isocyanates and isothiocyanates to get the final products. The results showed that all the synthesized compounds inhibited the carbonic anhydrase isoenzyme activity; 4c (IC50 = 66.23 µM for hCA I) and 4f (IC50 = 63.09 µM for hCA II) have the most inhibitory effect. The synthesized compounds are very bulky to be able to bind near the zinc ion and they much more probably bind as the coumarins and activators.

In vitro inhibition effect of some chalcones on erythrocyte carbonic anhydrase I and II

Abstract In this study, 4’-(phenylurenyl/thiourenyl)chalcones (14–25) were prepared from 4’-(phenylurenyl/thiourenyl)acetophenones and benzaldehyde derivatives by Claisen-Schmidt condensation. In vitro inhibition effects of chalcone derivatives on purified carbonic anhydrase I and carbonic anhydrase II were investigated by using the CO2 hydration method of Maren. The result showed that all the synthesized compounds inhibited the CA isoenzymes activity. 18 and 19 were found to be most active (IC50 = 25.41 μM and 23.06 μM) for hCA I, respectively. For hCA II, 24 is the most active compound (IC50 = 14.40 μM).

In vitro inhibition of polyphenol oxidase by some new diarylureas.

A new series of N,N′-diarylureas (1–9) was synthesized. These compounds were investigated as inhibitors of polyphenol oxidase (PPO) which had been purified from banana by an affinity gel comprised of Sepharose 4B-l-tyrosine-p-amino benzoic acid. Ki values for (1), (2), (3), (5), (6), (7) and (8) were determined as 0.285, 17.97, 0.187, 0.108, 0.063, 0.044 and 0.047 mM, respectively. Thus (2) was by far the most effective inhibitor. Interestingly, (4) and (9) behaved as an activator of PPO in this study.

Synthesis and carbonic anhydrase inhibitory properties of 1,3-dicarbonyl derivatives of methylaminobenzene-sulfonamide

Abstract 1,3-Dicarbonyl derivatives of methylaminobenzene-sulfonamide were synthesized and their inhibitory effects on the activity of purified human carbonic anhydrase (hCA) I and hCA II were evaluated. hCA I and hCA II from human erythrocytes were purified by a simple one-step procedure by using Sepharose 4B-L-tyrosine-sulfanilamide affinity column. Our results show that the synthesized compounds inhibited the activity of carbonic anhydrase (CA) I and CA II. Among them, 2b and 2e were found to be the most active (IC50 = 2.12 and 2.52 µM) for hCA I and hCA II, respectively.

Synthesis, structure-activity relationships and biological activity of new isatin derivatives as tyrosinase inhibitors.

A newly series of isatin derivatives (6a-t) containing alkyl/aryl urea groups were synthesized and their inhibitory effects on the diphenolase activity of banana tyrosinase were evaluated. Tyrosinase was purified from banana on an affinity gel comprised of Sepharose 4B-L-tyrosine-p-aminobenzoic acid. The results showed that all the synthesized compounds inhibited the tyrosinase enzyme activity. Among them, 1-(2,3-dioxoindolin-5-yl)-3-(4-nitrophenyl)urea (6l) was found to be most active compound (Ki = 24.96 µM). The inhibition kinetics was analysed by Lineweaver-Burk double reciprocal plots. It revealed that compound 6l was a competitive inhibitor. According to results of structure-activity relationship, generally, the compounds electron-donating group bonded to the phenyl ring have higher inhibitory activity against tyrosinase than halogen group bonded to the phenyl ring. The inhibitory activities of alkyl urea substituted compounds decreased with increasing carbon number of the alkyl groups at urea moiety. The halogen series at the para position of the phenyl ring showed a qualitative relationship for higher inhibitory activity with increasing size and polarizability. HOMOLUMO energy levels and dipole moments of some selected compounds (6a, 6d, 6h, 6l and 6o) were also calculated by Gaussian software.