Phytochemical Screening and Antibacterial Activity Test of Rice Bran Ethanol Extract (Oryza sativa L.) on Membrane Leakage in Staphylococcus aureus / Skrining Fitokimia dan Uji Aktivitas Antibakteri Ekstrak Etanol Dedak Padi (Oryza sativa L.) terhadap Kebocoran Membran Bakteri Staphylococcus aureus

Background: Rice bran is commonly utilized only as animal feed and is often regarded as a byproduct of rice milling. However, rice bran contains flavonoid compounds that exhibit antibacterial activity. This study aims to explore the potential of rice bran as an antibacterial agent, specifically against Staphylococcus aureus, through antibacterial activity testing and analysis of cell membrane leakage mechanisms. Objective: This research aims to utilize rice bran by evaluating its antibacterial activity and its mechanism of bacterial membrane leakage against Staphylococcus aureus. Methods: This experimental study involved the collection of rice bran samples, plant determination, simplicia characterization, and extraction using maceration with 96% ethanol. Phytochemical screening was conducted to identify active compounds, while antibacterial activity was tested using the disk diffusion method (Kirby-Bauer) at concentrations of 10%, 12.5%, 25%, 50%, 70%, and 80%. The membrane leakage mechanism was assessed by measuring nucleic acid and protein leakage (UV-Vis spectrophotometry) as well as Ca²⁺ and K⁺ ion release (atomic absorption spectrophotometry, AAS). Data were statistically analyzed using SPSS. Results: The ethanolic extract of rice bran yielded a 26.38% extraction yield and contained secondary metabolites, including alkaloids, flavonoids, tannins, saponins, triterpenoids/steroids, and glycosides. The antibacterial assay revealed inhibition zones classified as strong activity. Furthermore, rice bran extract induced membrane leakage in S. aureus, evidenced by increased mean absorbance values and standard deviations for DNA, protein (UV-Vis spectrophotometry), and Ca²⁺ and K⁺ ions (atomic absorption spectrophotometry) with rising extract concentrations. Conclusion: Rice bran exhibits potential as an antibacterial agent against Staphylococcus aureus through a membrane leakage mechanism. These findings support the utilization of rice bran not only as animal feed but also as a source of bioactive antimicrobial compounds.

Latar Belakang: Dedak padi umumnya hanya dimanfaatkan sebagai pakan ternak dan sering dianggap sebagai limbah dari proses penggilingan padi. Padahal, dedak padi mengandung senyawa flavonoid yang memiliki aktivitas antibakteri. Penelitian ini bertujuan untuk mengeksplorasi potensi dedak padi sebagai agen antibakteri, khususnya terhadap Staphylococcus aureus, melalui uji aktivitas antibakteri dan mekanisme kebocoran membran sel. Tujuan Penelitian: Penelitian ini bertujuan untuk memanfaatkan dedak padi dengan menguji aktivitas antibakterinya serta mekanisme kebocoran membran sel bakteri Staphylococcus aureus. Metode: Penelitian eksperimental ini meliputi pengumpulan sampel dedak padi, determinasi tumbuhan, karakterisasi simplisia, dan ekstraksi menggunakan metode maserasi dengan pelarut etanol 96%. Skrining fitokimia dilakukan untuk mengidentifikasi senyawa aktif, sedangkan uji aktivitas antibakteri menggunakan metode difusi cakram (Kirby-Bauer) pada konsentrasi 10%, 12,5%, 25%, 50%, 70%, dan 80%. Mekanisme kebocoran membran sel diuji melalui pengukuran kebocoran asam nukleat, protein (spektrofotometer UV-Vis), serta ion logam Ca²⁺ dan K⁺ (spektrofotometer serapan atom/AAS). Data dianalisis secara statistik dengan SPSS. Hasil Penelitian: Ekstrak etanol dedak padi menghasilkan rendemen sebesar 26,38% dan mengandung alkaloid, flavonoid, tanin, saponin, triterpenoid/steroid, serta glikosida. Uji antibakteri menunjukkan zona hambat yang termasuk dalam kategori aktivitas kuat. Selain itu, ekstrak dedak padi menyebabkan kebocoran membran sel S. aureus, ditandai dengan peningkatan absorbansi DNA, protein, serta ion Ca²⁺ dan K⁺ seiring dengan meningkatnya konsentrasi ekstrak. Kesimpulan: Dedak padi memiliki potensi sebagai agen antibakteri terhadap Staphylococcus aureus melalui mekanisme kebocoran membran sel. Temuan ini mendukung pemanfaatan dedak padi tidak hanya sebagai pakan ternak, tetapi juga sebagai sumber senyawa bioaktif antimikroba.