Antibacterial Activity of Lotus (Nelumbo nucifera Gaertn.) Leaf Ethanol Extract against Escherichia coli and Staphylococcus aureus / Uji Aktivitas Antibakteri Ekstrak Etanol Daun Seroja (Nelumbo nucifera Gaertn.) terhadap Escherichia coli dan Staphylococcus aureus

Introduction: The increasing occurrence of bacterial infections and antimicrobial resistance has encouraged the investigation of medicinal plants as potential sources of antibacterial compounds. Lotus (Nelumbo nucifera Gaertn.) leaves contain several classes of secondary metabolites that may contribute to antibacterial activity. Objective: This study evaluated the antibacterial activity of lotus leaf ethanol extract against Escherichia coli and Staphylococcus aureus and identified the major classes of secondary metabolites present in the extract. Methods: This laboratory experimental study used lotus leaf extract prepared by maceration with 96% ethanol. The simplicia was characterized and subjected to phytochemical screening. Antibacterial activity was evaluated using the paper-disc diffusion method on Mueller–Hinton agar at extract concentrations of 10%, 15%, and 20%, with clindamycin as the positive control and dimethyl sulfoxide as the negative control. Each treatment was tested in triplicate. Inhibition-zone diameters were analyzed using one-way analysis of variance followed by Tukey's HSD test. Results: The lotus leaf material contained alkaloids, flavonoids, saponins, tannins, steroids, and triterpenoids. Against E. coli, the mean inhibition-zone diameters at concentrations of 10%, 15%, and 20% were 13.60, 15.40, and 16.60 mm, respectively; the corresponding values against S. aureus were 14.56, 15.21, and 18.13 mm. Differences among treatments were statistically significant for both test bacteria (p<0.001). Conclusion: Lotus leaf ethanol extract exhibited concentration-dependent antibacterial activity against E. coli and S. aureus, with the strongest inhibition observed at 20%. Further studies should determine the minimum inhibitory and bactericidal concentrations and characterize the active antibacterial constituents.

Pendahuluan: Meningkatnya kejadian infeksi bakteri dan resistensi antimikroba mendorong eksplorasi tumbuhan obat sebagai sumber senyawa antibakteri. Daun seroja (Nelumbo nucifera Gaertn.) mengandung berbagai golongan metabolit sekunder yang berpotensi berkontribusi terhadap aktivitas antibakteri. Tujuan: Penelitian ini bertujuan mengevaluasi aktivitas antibakteri ekstrak etanol daun seroja terhadap Escherichia coli dan Staphylococcus aureus serta mengidentifikasi golongan metabolit sekundernya. Metode: Penelitian eksperimental laboratorium ini menggunakan ekstrak daun seroja yang dibuat melalui maserasi dengan etanol 96%. Simplisia dikarakterisasi dan diskrining secara fitokimia. Aktivitas antibakteri diuji menggunakan metode difusi cakram pada Mueller–Hinton agar dengan konsentrasi ekstrak 10%, 15%, dan 20%; klindamisin digunakan sebagai kontrol positif dan dimetil sulfoksida sebagai kontrol negatif. Setiap perlakuan diuji sebanyak tiga kali. Diameter zona hambat dianalisis menggunakan ANOVA satu arah dan dilanjutkan dengan uji Tukey HSD. Hasil: Bahan uji daun seroja mengandung alkaloid, flavonoid, saponin, tanin, steroid, dan triterpenoid. Rerata diameter zona hambat terhadap E. coli pada konsentrasi 10%, 15%, dan 20% berturut-turut sebesar 13,60; 15,40; dan 16,60 mm, sedangkan terhadap S. aureus sebesar 14,56; 15,21; dan 18,13 mm. Terdapat perbedaan bermakna antarperlakuan pada kedua bakteri uji (p<0,001). Kesimpulan: Ekstrak etanol daun seroja menunjukkan aktivitas antibakteri yang meningkat seiring kenaikan konsentrasi terhadap E. coli dan S. aureus, dengan penghambatan terbesar pada konsentrasi 20%. Penelitian lanjutan diperlukan untuk menetapkan konsentrasi hambat dan bunuh minimum serta mengidentifikasi senyawa aktif antibakterinya.