Antibacterial Activity Test of Fractionated Alkaloid Extract from Raru Bark (Cotylelobium melanoxylon Pierre) Against Escherichia coli and Staphylococcus aureus Bacteria / Uji Aktivitas Antibakteri Fraksinasi Alkaloid Ekstrak Kulit Kayu Raru (Cotylelobium melanoxylon Pierre) Terhadap Bakteri Escherichia coli dan Staphylococcus aureus

Background: Indonesia is rich in medicinal plants, including Cotylelobium melanoxylon Pierre (raru bark), traditionally used to treat diarrhea, malaria, and diabetes. However, scientific validation of its alkaloid compounds and antibacterial potential is still limited. Objective: This study aimed to (1) fractionate alkaloids from raru bark extract using chloroform liquid-liquid extraction, (2) identify alkaloid functional groups via FT-IR spectroscopy, (3) quantify alkaloid levels in ethanol and methanol extracts using UV spectrophotometry, and (4) evaluate their antibacterial activity against Escherichia coli and Staphylococcus aureus. Methods: The research stages included plant material processing, ethanol/methanol extraction, phytochemical screening, alkaloid fractionation with chloroform, FT-IR analysis, UV spectrophotometry for alkaloid quantification, and antibacterial testing via disc diffusion at 40%, 50%, and 60% concentrations. Results: Alkaloid fractions were successfully isolated, containing functional groups N-H, C-N, C=O, aromatic C=C, and sharp C=O. The methanol extract yielded higher alkaloid levels (21.03 ± 0.10%) than ethanol (18.95 ± 0.09%). The 50% alkaloid fraction showed the strongest antibacterial activity, with inhibition zones of 21.1 mm (E. coli) and 23.1 mm (S. aureus). Conclusion: Raru bark alkaloids exhibit significant antibacterial effects, with methanol extract demonstrating superior alkaloid content and efficacy.

Latar Belakang: Indonesia memiliki keanekaragaman tumbuhan obat, termasuk kulit kayu raru (Cotylelobium melanoxylon Pierre) yang secara empiris digunakan untuk mengobati diare, malaria, dan diabetes. Namun, validasi ilmiah senyawa alkaloid dan potensi antibakterinya masih terbatas. Tujuan: Penelitian ini bertujuan untuk (1) memfraksinasi alkaloid ekstrak kulit kayu raru dengan ekstraksi cair-cair kloroform, (2) mengidentifikasi gugus fungsi alkaloid menggunakan spektroskopi FT-IR, (3) menentukan kadar alkaloid ekstrak etanol dan metanol dengan spektrofotometri UV, dan (4) menguji aktivitas antibakterinya terhadap Escherichia coli dan Staphylococcus aureus. Metode: Tahapan meliputi pengolahan sampel, ekstraksi etanol/metanol, skrining fitokimia, fraksinasi alkaloid, analisis FT-IR, penetapan kadar alkaloid, dan uji antibakteri dengan metode difusi cakram pada konsentrasi 40%, 50%, dan 60%. Hasil: Fraksi alkaloid berhasil diisolasi dan mengandung gugus fungsi N-H, C-N, C=O, C=C aromatik, dan C=O tajam. Kadar alkaloid tertinggi ditemukan pada ekstrak metanol (21,03 ± 0,10%) dibanding etanol (18,95 ± 0,09%). Fraksi 50% menunjukkan aktivitas antibakteri terkuat dengan zona hambat 21,1 mm (E. coli) dan 23,1 mm (S. aureus). Kesimpulan: Alkaloid kulit kayu raru efektif sebagai antibakteri, dengan ekstrak metanol memberikan kadar dan aktivitas lebih optimal.