Sintesis dan uji aktivitas antibakteri secara in vitro senyawa turunan N-asetil pirazolina tersubstitusi gugus hidroksi berbahan dasar vanilin

OKTA SURYANI, Dr. Tutik Dwi Wahyuningsih, M.Si; Prof. Dr. Harno Dwi Pranowo, M.Si.

2014 | Tesis | S2 Ilmu Kimia

Telah dilakukan sintesis turunan senyawa N-asetil-2-pirazolina dan uji antibakterinya secara in-vitro. Sintesis senyawa pirazolina dilakukan melalui reaksi sikloadisi antara 1-(2,4-dihidroksifenil)-3-(3,4- dimetoksifenil)-2-propen-1-on (kalkon 1) dan 1-(2,4-dihidroksifenil)-3-(4-hidroksi-3-metoksifenil)-2-propen-1-on (kalkon 2) dengan hidrazin monohidrat dalam suasana asam. Senyawa kalkon disintesis dari vanilin dan veratraldehida dengan 2,4 dihidroksiasetofenon melalui kondensasi Claisen Schmidt dalam suasana basa. Senyawa kalkon 1 disintesis dari veratraldehida menggunakan KOH 40% (b/b dalam akuades) melalui pengadukan selama 48 jam pada temperatur kamar. Senyawa kalkon 2 disintesis dari vanilin dengan penambahan KOH 40% dan katalis KSF montmorilonit melalui pengadukan pada temperatur kamar selama 48 jam dilanjutkan dengan refluks selama 24 jam. Kalkon 1 dan 2 masing-masing direaksikan dengan hidrazin monohidrat sehingga menghasilkan senyawa 1-asetil-3-(2,4-dihidroksifenil)-5-(3,4-dimetoksifenil)-2-pirazolina (pirazolina 1) dan 1-asetil- 3-(2,4-dihidroksifenil)-5-(4-hidroksi-3-metoksifenil)-2-pirazolina (pirazolina 2). Reaksi dilakukan dengan metode refluks selama 4 jam dalam pelarut metanol menggunakan katalis asam asetat glasial. Produk hasil sintesis dikarakterisasi dengan spektrometer FT-IR, GC-MS, 1H- dan 13C-NMR. Uji antibakteri dilakukan dengan metode difusi sumuran terhadap bakteri Gram positif (Staphylococcus aureus, Bacillus cereus, Bacillus subtilis) dan Gram negatif (Eschericia coli, Shigella flexneri) dengan kontrol positif tetrasiklin (100 ppm) dan kontrol negatif dimetilsulfoksida DMSO (99,9%). Hasil penelitian menunjukkan bahwa senyawa kalkon 1 dan 2 telah berhasil disintesis dengan rendemen masing-masing sebesar 80,91 dan 68,90%. Senyawa target pirazolina 1 dan 2 telah berhasil disintesis dengan rendemen masing-masing sebesar 55,56 dan 66,10%. Senyawa pirazolina 1 menunjukkan aktivitas sebagai antibakteri pada bakteri Gram positif namun tidak memiliki aktivitas terhadap bakteri Gram negatif. Aktivitas tertinggi ditunjukkan dengan nilai DDH (mm)/konsentrasi (ppm) terhadap Staphylococcus aureus (9,75/300). Senyawa pirazolina 2 menunjukkan aktivitas sebagai antibakteri pada bakteri Gram positif dan Gram negatif. Aktivitas tertinggi terhadap bakteri Gram positif Bacillus subtilis (8,00/300) dan Gram negatif yaitu Escherichia coli (4,50/500).

Synthesis of N-acetyl-2-pyrazoline derivatives and their antibacterial activity have been carried out. The synthesis of pyrazolines were performed via cycloaddition of 1-(2,4-dihydroxyphenyl)-3-(3,4- dimethoxyphenyl)-2-propen-1-on (chalcone 1) and 1-(2,4-dihydroxyphenyl)-3-(4-hydroxy-3-methoxyphenyl)-2-propen-1-on (chalcone 2) by reaction with hydrazine monohydrate in acidic condition. Chalcones were synthesized from vanillin and veratraldehyde by reaction with 2,4-dihydroxyacetophenone through Claisen Schmidt condensation. Chalcone 1 was synthesized from veratraldehyde using KOH 40% (w/w in aquadest) under stirring at room temperature for 24 h. Chalcone 2 was produced by stirring the mixture of vanillin with KOH 40% for 48 h and refluxing for 24 h, continually. Synthesis of 1-acetyl-3-(2,4-dihydroxyphenyl)-5-(3,4-dimethoxyphenyl)-2-pyrazoline (pyrazoline 1) and 1-acetyl- 3-(2,4-dihydroxyphenyl)-5-(4-hiydroxy-3-methoxyphenyl)-2-pyrazoline (pyrazoline 2) were performed by refluxing chalcone 1 and 2 by reaction with hydrazine monohydrate in glacial acetic acid for 4 h. All the synthesized compounds were characterized using FTIR, GC-MS 1H- and 13C-NMR spectrometers. Further, all the pyrazolines (1 and 2) were screened for their in-vitro antibacterial activities by agar well-diffusion against Gram positive (Staphylococcus aureus, Bacillus cereus, Bacillus subtilis) and negative (Eschericia coli, Shigella flexneri) bacterial, tetracycline (100 ppm) as positive control and dimethylsulfoxide (DMSO 99.9%) as negative control. The result showed that chalcones 1 and 2 have been succesfully synthesized in 80.91 and 68.90% yield, respectively. Furthermore, the cycloaddition reaction yielded the pyrazoline 1 and 2 in 55.56 and 66.10%, respectively. Pyrazoline 1 showed significant antibacterial activity against Gram-positive bacterial and found inactive against Gram negative bacterial. The highest activity showed by its zone of inhibitions(mm)/concentration(ppm) against Staphylococcus aureus (9.75/300). Good antibacterial activity for both Gram negative and positive bacterial was observed for Pyrazoline 2. Zone of inhibitions for gram positive showed by Bacillus subtilis (8.00/300) and Gram-negative Escherichia coli (4.50/500).

Kata Kunci : N-asetil-2-pirazolina, kalkon, vanilin, veratraldehida, antibakteri