Three types of coumarin derivatives were synthetised using the Knoevenagel condensation technique. All of these compounds have been characterised by the Fourier Transform Infrared (FTIR) and the Nuclear Magnetic Resonance (NMR) spectroscopy (1H NMR, 13C NMR) to evaluate their chemical properties. The first step of synthesis involved preparing 3-acetylcoumarin 1 followed by the synthetisation of hydrazine thiosemicarbazide coumarin derivative 2 by treating thiosemicarbazide in the presence of a catalytic amount of glacial acetic acid. The hydrazinyl thiazolyl of coumarin derivative 3 was prepared using the cyclisation of compound 2 with 3- bromoacetylcoumarin. The presence of the hydrazine and thiazole groups of the latter synthetised derivatives were confirmed using an NMR analysis that depicted the bond attachment of the imine and thiazole groups in the molecular structure of the first derivative 1. An in-vitro cytotoxicity study of the synthetised coumarin derivatives were screened using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay on Human Periodontal Ligament Fibroblast (HPDLF) cells. The cytotoxicity study demonstrates that the coumarin derivatives which contain the hydrazinyl thiazolyl group exhibit less toxicity values at a concentration of 5.51 mM for a half maximal inhibitory concentration (IC50). The heterocyclic groups of the derivatives backbone will eventually contribute to promising biological properties of a biomaterial.