Breast cancer is considered as one of the most common cancers all over the world. A huge effort has been made to create a safe and cost effective breast cancer treatment. All of these features exist in the plants sources. In this study, the effect of local vegetable salad, Premna serratifolia (Bebuas) against MCF-7 cells (human breast adenocarcinoma) was determined. The optimum condition to extract breast cancer cytotoxic compound from the plant was investigated and the exact cytotoxic compound was identified as well. To determine the plant cytotoxicity effect against MCF-7 cells, MTT assay was used. Two important parameters in the sonication extraction method which are duration of time and temperature were optimized by carrying out a series of experiments which were designed by Face Centered Central Composite Design (FCCCD). The extraction efficiency of each experiment was determined by measuring the yield of extract and the half maximal inhibitory concentration (IC50) of the extract against MCF-7 cells. The results obtained from the experiments were fitted to the second order polynomial model to generate equation that was used to determine best extraction processing condition. Based on the generated equation, the best sonication processing condition to extract the cytotoxic compound is at 30oC for 67 min. Analysis of variance (ANOVA) showed that the duration of extraction time has great influence (p<0.05) on the yield of crude extract, while both parameters, time and temperature significantly (p<0.05) affected the IC50 value of the plant extract. Two purified compounds from the plant, acacetin and acacetin-7-O-glycoside were identified to be responsible for the cytotoxicity activity. Conclusively, in terms of pharmaceutical and medical field applications; the optimal extraction processing condition obtained from this study ensures that the extraction of cytotoxic compound from the plant is conducted at the low temperature and short duration of time. Further study on the identified compounds is required as it is a potential candidate for anticancer drug.