in Vitro Antimicrobial Activities of Some Schiff Bases · and Their Ni (il) Complexes

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FABAD]. Pharm. Sci., 19, 5-8, 1994

BILIMSEL ARAŞTIRMALAR / RESEARCH ARTICLES

in Vitro Antimicrobial Activities of Some Schiff Bases · and Their Ni (il) Complexes

Fatma GÜMÜŞ*, Perihan GÜRKAN**, Necla GÜNDÜZ***, Ufuk ABBASOGLU****

Summary: In this study, in vitro antimicrobial activities of a series of 5-and/or-5 '-substituted-N-salicylidene-o- hydroxyanilines and their Ni (II) complexes were investi- gated with the aim of revealing ^therelationship between the structures and· the biological activities of the com- pounds.

Ali the compounds of which synthesis and structure elu- cidations reported in a previous paper^1, were tested for their in vitro antimicrobial activites against some Gram- positive (Staphylococcus aureus) and Gram-negative (Escherichia cali) bacteria and some yeast-like fungi (Candida albicans and Candida parapsilosis) with Mi- crodilution Broth Method.

The test results showed that, the Ni ^(II)complexes of the Schiff bases tested were equally or less active against all of the microorganisms used titan their corresponding li- gands. It was seen that, in general, in vitro antifungal ac- tivities of the ligands and their Ni (II) complexes were higher than their in vitro antibacterial activities. It was determined that most of· the ligands and the complexes had MIC (minimum Inhibitory Concerıtration) values of 25-50 µg/mL against the bacteria used and most of the ligands hal more antifungal activity (MIC: 12.5 µg/mL) than their Ni (II) complexes.

Keywords Schiff Bases, N-salicylidene-o- hydroxyanilines, Ni ^(II)complexes of N-

salicylidene-o-hydı:oxyanilines, in vitro antibacterial activity, in vitro antifungal activity.

Geliş tarihi 6.7.1993 Kabul tarihi : 10.11.1993

(*) Gazi University, Faculty of Pharmacy, Department of Pharmaceutical Chemistry, 06330, Ankara-TÜRKIYE . . (**) Gazi University, Science and .fut Faculty, Department of

Oıemistry, 06330, Ankara-TURKIYE.

(***) Ankara University, Faculty .'?f Science, Department of Chemistry, ^06100ı.Ankara-TURKIYE.

(****) Gazi University, Faculty of PI'!armacy, Depaı;tment of Microbiology, 06330, Ankırra-TÜRKIYE.

Bazı Schift Bazları ve Ni (II) Kompleks'lerinin fn Vitro Antimikrobiyal Aktiviteleri

Özet: Bu çalışmada, yapıları ile biyolojik aktiviteleri

arasındaki ilişkiyi araştırmak amacı ile bir seri 5-ve/veya- 5 '-sübstitüe-N-salisiliden-o-hidroksianilin türevi ^bileşiğin ve bu bileşiklerin Ni .(Il) komplekslerinin in vitro antimik- robiyal aktivite çalışmaları yapıldı.

Daha iinceki bir ^çalışmada¹ sentez ve yapı aydınlatmaları bildirilmiş olan tüm bileşiklerin, bazı Gram-pozitif (Stap- hylococcus aureus) ve Gram-negatif (Escherichia coli) bakteri türlerine ve ^bazımaya benzeri mantarlara (Candi- da albicans ve Candida parapsilosis) ^karşıolan in vitro an- timikrobiyal aktiviteleri Mikrodilüsyon Broth ^yönteıiıi

kullanılarak denendi.

Test sonuçları, Schiff bazlarının Ni (II) komplekslerinin,

kullanılan tüm mikroorganizmalara ^karşıolan antimikro- biyal aktivitelerinin ligandları ile aynı veya onlarınkinden

daha az olduğunu gösterdi.

Genel olarak, ligandların ve komplekslerin in vitro anti- fungal aktivitelerinin, in vitro antibakteriyel f}ktivitelerin- den daha fazla olduğu görüldü. Ligandların ve Ni ^(II) komplekslerinin çoğunun kullanılan bakterilere karşı 25- 50 µg/mL (MIK (Minimum Inhibisyon Konsantrasyonu)

değerlerine sahip olduğu ve ligantların çoğunun antifun- gal aktivitelerinin (MIK ⁼12.5 µg/mL) Ni ^(Il)kompleksle- rinin antifungal aktivitilerinden daha fazla ^olduğusap-

tandı.

Anahtar Sözcükler

Inlroduction

Schiff Bazları, N-salisiliden-o- hidroksianilinler, N-salisiliden- o-hidroksianilinlerin Ni ^(II) kompleksleri, in vitro antibak- teriyel aktivite, in vitro antifun- gal aktivite.

Schiff Bases and their metal complexes find re- markable applications in pharmacology. They are known to possess antibacterial, antifungal, antitu- berculotic and antitumor activities2.

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Gümüş et all.

With the exception of a few reports mentioned about antibacterial activies of 5-bromo3,4, 5- methly4 and 5'-chloro3 substituted salicylidene-o- hydroxyanilines, antibacterial4, herbicidalS, anti- fungal6, plant growth inhibitor7, antitumor8 activities have been reported for some salicylidene-o- hydroxyanilines but not far its 5-and/or 5'- substituted derivatives.

lt was alsa reported that Co (Il) complex of salicylidene-o-hydroxyaniline had antitumor9, antiim- flammatory 10 activities and Cu (Jl) and Ni (II) complexes of the mentioned compound had antiim- flammatory 11 and antifungaJlO activities respec- tively.

As it is well known that many biological processes involve hydrolysis of proteins and peptides and cer- tain proteolytic enzymes require metal ions for their activities and hydrolysis reactions. it is alsa well known that there are some relationships between the antimicrobial activities of some ligands and the metaJs12. It was therefore planed to test the in vitro antimicrobial activities of some 5-and/ or-5'- substituted-N-salicylidene-o-hydroxyanilines and their Ni (Il) complexes aganist some Gram-positive and Gram-negative bacteria and some yeast like fungi in order to determine whether there is a structure-activity relationships between the ligands and their Ni (!!) complexes.

Materials and Methods

Synthesis of the Ligands and Their Ni (Il) Complexes:

Figure 1. The general structure of the ligands

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Figure 2. The pseudo-octahedral structure of the complexes

The synthesis and the structure elucidations of the compounds were reported in a previous paperl.

The ligands (Figure 1) derived from salicylalde- hyde and o-hydroxyaniline were synthesized by using appropriate amines and aldehydes.

All Ni (II) complexes of the ligands were prepared from equimolar amounts of the ligand and nickel- ll-acetate.

The composition and the structures of Ni (Il) complexes were elucidated on the hasis of elemental analysis, magnetic susceptibility measurements, in- frared spectra and electronic spectra.

Ali of the complexes were found to have a pseudo- octahedral structure (Figure 2).

Microbiological Methods

The in vitro antimicrobial activity of the compounds was tested by Microdilution Broth Methodl3.

Test Microorganisms and Culture Media:

Microorganisms utilized in the assay included S.

aureus ATCC 25923, E. coli ATCC 25922, C. albicans, C. parapsilosis.

Mueller-Hinton Broth (Oxoid) was used for dilut- ing bacteria suspension and for two-fold dilution of the compounds.

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Pluırm. Sci., 19, 5-8, 1994

Sabouraud Liquid medium (Oxoid) was used for yeast-like fungi for the same purpose.

Equipmen!:

FalconR microplates which have 96 wells were used for microdilution method. Brinkman transfer pipet- teR was used for two-fold dilution of the test compounds in the wells.

in Vitro Antimicrobial Assays:

0.1 mi of Müeller-Hinton Broth or Sabouraud Liquid Medium were placed into each well of microplates.

Each of the compounds tested and the standards ampicillin trihidrate and clotrimazole were dis- solved in DMSO at 800 µg/ml concentrations.

The two-fold dilutions of the compounds (400, 200, 100, ... , 3.125 µg/ mL) were made by dispensing the stock solutions to the remaining wells.

Suspensions of microorganisms at ¹⁰⁶CFU /mi concentration were inoculated ^ıothe two-fold diluted

solution of the compounds, consequently the micro- organism concentrations in each well were approxi- mately 5xlü4 CFU / mL.

Minimum inhibitory concentrations (MIC's) were defined as the lowest concentration of the compounds that inhibited visible growth of microorganisms after incubation at 36"C for 16 hours for bacteria or 48 hours far yeast like fungi in the humid chamber. ^Itwas determined that the solvent had no antimicrobial activity against any of the test microorganisms. MIC values of the compounds are presented in Table 1.

Results and Discussion

The in vitro antibacterial activity of the compounds against S. aureus and E. cali and the in vitro antifungal activity of the compounds against C. albicans and C. parapsilosis are presented in Table ^l.

The data for ampicillin trihidrate and clotrimazole are included far comparison. A comparative study of the MIC values indicated that the in vitro antimicrobial activities of ali the compounds tested were less than that of standard ampicilline tri-

Table 1. in Vitro Antimicrobial Activity Data of the Schiff Bases and their Ni (II) Cornplexes

&·J-©

1 1

R

".

MIC(µg/mL) MIC(µg/mL)

R R' Compound S.a.a E.c.b C.a.c C.p.d R R' Compound ^S.a.a ^E.c.b ^C.a.c ^C.p.d

H H 11 12.5 25 12.5 12.5 H H Ni(IJ)Ll 12.5 25 25 12.5

a

^H ¹² ²⁵ ⁵⁰ ^12.5 ^12.5

a

^H ^Ni(IJ)L2 ⁵⁰ ⁵⁰ ⁵⁰ ⁵⁰

Br H 13 50 ¹⁽⁾⁽⁾ 50 50

NO, H IA 50 50 25 12.5 N02 H Ni(IIJL4 50 50 50 50

oı, H 15 50 50 25 12.5 oı, H Ni(IJ)L5 50 50 25 25

H

a

^u; ²⁵ ²⁵ ^12.5 ^12.5 ^H

a

^Ni(!J)L6 ²⁵ ⁵⁰ ^12.5 ^12.5

H Br 17 25 25 12.5 12.5 H Br Ni(l!)L7 25 50 25 12.5

H N0₂ Ni(Il)5'-N0₂ 25 50 50 50

H CH3 lB 25 50 12.5 12.5 H CH, Ni(II)LB 50 50 25 25

a a

¹⁹ ^12.5 ²⁵ ^12.5 ^12.5

a a

^Ni(I!)L9 ⁵⁰ ⁵⁰ ²⁵ ²⁵

Br ^Br ^LlO ²⁵ ⁵⁰ ²⁵ ²⁵

N0₂ N0₂ L11 50 50 25 12.5 Br Br ^Ni(I!)LlO ²⁵ ⁵⁰ ²⁵ ²⁵

NO, NO, Ni(IJ)Lll 50 50 50 50

oı, oı, L12 50 50 12.5 12.5 CH, ^oı, Ni(IJ)L12 100 100 100 50

Ampicillin 6.25 6.25

trihidrate

Ootrimazole 6.25 6.25

a Staphylococciıs aureus, bEscherichia cali, CCandida albicans, dCandida parapsilosis

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Gümüş et all.

hidrate and clotrimazole. The Ni (II) complexes of the Schiff bases tested were equally or less active against ali of the rnicroorganisms used than their corresponding ligands. in general, in vitro antifungal activities of the Schiff bases and the cornplexes were higher than their in vitro antibacterial ac- ti vi ties.

Most of the ligands had rnore in vilro antifungal activity agamst. C. albicans and C. parapsilosis than their corresponding Ni (II) cornplexes. Except far L5, L6, L10, ali the ligands had 2-4-fald rnore antifungal activity against C. albicans than their corresponding cornplexes.

Except far Ll, L6, L7, L10, the ligands gave 2-3-fold better activity against C. parapsilosis than the cornplexes.

It was seen that 5,5'-dichloro and 5.5'-dirnethyl substituted-N-salicylidene-o-hydroxyanilines (L9 and L12) were rnore active against ali the rnicroorganisrns tested than their cornplexes [Ni (!I) L9 and Ni (II) L12

J.

it was observed that there was not any relation- ship between the type (electron donar or acceptor) and the position of the substituents and the activity. It is interesting to note that except far L9, unsubstituted salicylidene-o-hydroxyaniline (Ll) and its Ni (II) cornplex (Ni(Il)Ll) are rnore active gainst S.

aureus than their derivatives substituted with electron donar and/ or electron acceptor groups. Ex- cept far L6, L7, L9, unsubstituted salicylidene-o- hydoroxyaniline (Ll) and its Ni (lI) cornplex are rnore active against E. coli than their substituted derivatives.

Theoretically, it is possible to say that, since the ligands investigated have a higher antifungal activity than their Ni (il) cornplexes, the ligands rnay form a cornplex with sorne of the trace ele- rnents of the rnicroorganisrns which are necessary far their growth.

References

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