<![CDATA[Abstract: Indonesia has a high diversity of flora and fauna in the world. Many types of plants can be used as a medicinal plant; one of them is yellow root (Arcengelisia flava Merr.) which has been known empirically by the Dayak community in Central Kalimantan as natural herbs to treat jaundice. This study aimed to determine the antibacterial effect of the yellow root bark extract against Staphylococcus aureus and Escherichia coli. This study was conducted in the Laboratory of Pharmacology and the Laboratory of Microbiology Faculty of Medicine University of Sam Ratulangi. This was an experimental laboratory study using the Kirby-Bauer modified technique. Yellow root bark extract was obtained from maceration process using ethanol 96%. The antibacterial effect was tested by using the well diffusion method. The results showed that distilled water, the negative control, did not generate inhibition zone around the wells. Ciprofloxacin, the positive control, had the greatest diameter of inhibitory zone. The average diameter of inhibition zone generated by ciprofloxacin was 39.23 mm against Staphylococcus aureus and 40.95 mm against Escherichia coli. Meanwhile, yellow root extract generated an average diameter inhibition zone of 12.27 mm against Staphylococcus aureus and 14.44 mm against Escherichia coli. Conclusion: Yellow root bark extract potentially had antibacterial effect against Staphylococcus aureus and Escherichia coli. Keywords: antibacterial, yellow root bark, Staphylococcus aureus, Escherichia coli. Abstrak: Indonesia memiliki keberagaman flora dan fauna yang tinggi di dunia. Banyak jenis tanaman yang dapat dijadikan sebagai tanaman obat, salah satunya akar kuning (Arcangelisia flava Merr.) yang telah lama dikenal secara empiris oleh masyarakat dayak di Kalimantan Tengah sebagai tanaman herbal alami untuk mengobati penyakit kuning. Penelitian ini bertujuan untuk mengetahui efek antibakteri dari ekstrak batang akar kuning terhadap bakteri Staphylococcus aureus dan Escherichia coli dan dilakukan di Laboratorium Farmakologi, dan Laboratorium Mikrobiologi Fakultas Kedokteran Universitas Sam Ratulangi. Jenis penelitian ini eksperimental laboratorium dengan metode modifikasi Kirby-Bauer. Uji efek antibakteri menggunakan metode sumuran. Esktrak batang akar kuning diperoleh dari proses maserasi dengan etanol 96%. Hasil penelitian memperlihatkan akuades sebagai kontrol negatif tidak menimbulkan zona hambat di sekitar sumur. Siprofloksasin sebagai kontrol positif memiliki diameter zona hambat yang paling besar. Rerata diameter zona hambat yang dihasilkan oleh siprofloksasin 39,23 mm terhadap Staphylococcus aureus dan 40,95 mm terhadap Escherichia coli. Ekstrak akar kuning menghasilkan rerata diameter zona hambat sebesar 12,27 mm terhadap Staphylococcus aureus dan 14,44 mm terhadap Escherichia coli. Simpulan: Ekstrak batang akar kuning berpotensi memiliki efek antibakteri terhadap bakteri Staphylococcus aureus dan Escherichia coli. Kata kunci: antibakteri, ekstrak akar kuning, staphylococcus aureus, escherichia coli]]>
