BIOPOLYMER-BASED EMULGEL OF KASTURI (CITRUS MICROCARPA BUNGE) ESSENTIAL OIL: STABILITY, SPF, ANTIOXIDANT, AND ANTIBACTERIAL PROPERTIES

Objective: To develop a biopolymer-based emulgel of kasturi essential oil and evaluate its physical stability, photoprotection, antioxidant, and antibacterial performance. Methods: Oil of kasturi was obtained by steam distillation and profiled by gas chromatography–mass spectrometry (GC–MS). Twelve formulations were prepared and subjected to stability, pH, viscosity, spreadability, and phase separation tests. Bioactivity assays included antioxidant activity using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) method, in vitro sun protection factor (SPF) with the Mansur method, and antibacterial activity against Staphylococcus aureus using the disc diffusion method. Results: Essential oil yield from fresh Citrus microcarpa peels obtained by non-optimised steam distillation was 0.34% w/w, which lies at the lower end of values reported for this species and other citrus peels under similar conditions; notably, optimized hydrodistillation of Citrus microcarpa can afford higher yields; density 0.84 g/mL; 41 compounds were identified (dominant D-limonene). Formula 2 (F2) (sodium carboxymethyl cellulose (Na-CMC)), formula 4 (xanthan gum), and formula 12 (sodium alginate) passed accelerated tests and remained stable under freeze–thaw. Antioxidant activity (inhibitory concentration 50% (IC₅₀), ppm): kasturi oil (95.905), F2, F4, and F12 (99.255-171.834). SPF values for F2, F4, and F12 were 19.38–44.13, and kasturi oil (12.20). Antibacterial testing against Staphylococcus aureus produced small inhibition zones; F2, F4, and F12 were 2.00–4.54 mm, far below the positive control chloramphenicol (31.50 ± 0.00 mm). Conclusion: F2, F4, and F12 were physically stable. F2 showed the highest in vitro SPF estimate, but this value is likely overestimated and requires in vivo confirmation before firm photoprotective claims can be made. All emulgel formulations exhibited a weak antibacterial effect, and the overall antioxidant activity of the oil was also very weak.