Aktivitas Antibakteri Sediaan Nanoemulsi Gel Minyak Jarak (Castor oil) terhadap Bakteri Propionibacterium acnes dan Staphylococcus aureus serta Mekanisme Kerjanya

Abstract

Background: Acne vulgaris is a chronic inflammatory skin condition associated with excessive sebum production, follicular blockage, and bacterial colonization, primarily by Propionibacterium acnes and Staphylococcus aureus. Castor oil (Ricinus communis L.) contains bioactive fatty acids with known antibacterial and anti-inflammatory activities, making it a potential candidate for topical anti-acne formulations. Objective: This study aimed to identify the chemical constituents of castor oil, formulate it into a nanoemulgel, evaluate its physicochemical characteristics, assess its antibacterial activity against Propionibacterium acnes and Staphylococcus aureus, and elucidate its antibacterial mechanism of action. Methods: The chemical composition of castor oil was analyzed by Gas Chromatography-Mass Spectrometry (GC-MS). Nanoemulgel formulations containing 1%, 2%, and 4% castor oil were prepared and evaluated for organoleptic properties, pH, viscosity, spreadability, particle size, stability, and antibacterial activity using the agar diffusion method. The antibacterial mechanism was investigated by measuring nucleic acid and protein leakage via UV-Visible spectrophotometry and ion leakage (Ca²⁺ and K⁺) via Atomic Absorption Spectrophotometry (AAS). Results: GC-MS analysis identified oleic, palmitic, and stearic acids as major components of castor oil. The nanoemulgel exhibited favorable physicochemical properties, particle sizes of 100–500 nm, and stability over 12 weeks at various storage conditions. The 4% formulation demonstrated the largest antibacterial inhibition zones. Mechanistic studies showed increased membrane permeability, evidenced by nucleic acid/protein leakage (absorbance 0,225 nm -0,419 nm) and ion leakage (Ca²⁺: 112.86–118.31 ppm; K⁺: 121.66–125.47 ppm). Conclusion: Castor oil nanoemulgel at 4% concentration exhibited promising stability and antibacterial activity, supporting its potential as a topical anti-acne treatment.