Armandela, DelvanEryanti, Yum2019-01-092019-01-092019-01-10wahyu sari yenihttp://repository.unri.ac.id/handle/123456789/9559Pyrazoline is an organic compound in alkaloid group with five-ring structure heterocyclic compound, containing three carbon atoms and two adjacent nitrogen atoms to one endocyclic double bond. Pyrazoline have various biological activities, such as antibacterial, anticancer, antiinflamatory, antidepressant, and antioxidant. The pyrazolines 3-(2-clorophenyl)-5-(2-methoxyphenyl)-1-phenyl-4,5-dihydropyrazole (PF-2Cl-2OMe) were synthesized by a one-pot three-component reaction between 2-methoxybenzaldehyde, 2-cloroacetophenone and phenylhydrazine with strong base catalyst (KOH) by microwave method. The purity of the compound was determined by the TLC test, the measurement of melting point and HPLC analysis. The structure of the synthesized compound was obtained from UV, FTIR, NMR and HRMS spectroscopy studies. It can be concluded that the optimum method to synthesize this compound is microwave method with yield of 40% and reaction time is relatively short. The toxicity of pyrazoline were evaluated by Brine Shrimp Lethality Test (BSLT) method. Pyrazoline PF-2Cl-2OMe compound showed non-toxic activity with LC50 = 226.46 μg/mL.enBrine Shrimp Lethality Testmicrowave irradiationpyrazolineArticle