Objective
The objective of the work was to optimize the brazilin content and antibacterial activity of Caesalpinia sappan L. heartwood extract using computer software.

Methods
Two independent factors were studied: extraction temperature (45–95 °C) and extraction time (30–60 min). In addition, five dependent factors were monitored, including extraction yield, brazilin content, and clear zones against Staphylococcus aureus TISTR 1466, Staphylococcus epidermidis TISTR 518 and Propionibacterium acnes DMST 14961. The brazilin content was quantified by high-performance liquid chromatography and antibacterial activity was determined by disc diffusion assay.

Results
The high temperature provided high total extract yield as well as brazilin content, while extraction time had little effect on yield or brazilin content. Extraction time had a positive effect, while extraction temperature had little effect on clear zone against S. aureus. The largest clear zone against S. epidermidis was achieved at low extraction temperature and high extraction time. Conversely, low extraction time and high extraction temperature provided the largest clear zone against P. acnes. The optimal conditions providing the highest brazilin content was an extraction temperature and extraction time of 95 °C and 30 min, respectively. The same optimal conditions also provided the simultaneous greatest antibacterial activity against the three bacteria. Modeled optimal conditions were validated be conducting extraction using these values. Yield and antibacterial activity of the resulting extract demonstrated that the model had a low percentage error.

Conclusion
The optimal condition will be used as a standard condition for extraction of C. sappan heartwood to maximize brazilin content and antibacterial activity.

Key words: Antibacterial activity, Brazilin, Caesalpinia sappan, Optimization