Microemulsion of essential oils from citrus peels and leaves with anti-aging, whitening, and irritation reducing capacity

Although citrus essential oil is frequently used in cosmetics as fragrance, the biological activities related to skin benefits have been rarely investigated. This study aimed to investigate the anti-skin aging and anti-melanogenic effects of citrus oils and develop microemulsion system to reduce the irritation capacity of citrus oils. Oils from leaves and fruit peels of Citrus aurantifolia (Christm.) Swing and Citrus reticulata Blanco cv. Shogun were from hydro-distillation. Their chemical composition was analyzed using gas chromatography/mass spectrometry. Antioxidant activities were determined in terms of free radical scavenging activities, ferric reducing antioxidant power, and lipid peroxidation inhibition. Anti-aging and anti-melanogenic activities were investigated using related enzyme activity analysis. Oils with the most potent biological activities were selected for further incorporation into microemulsion. The irritation capacity of native and citrus microemulsion were investigated in human volunteers. Citrus oils comprised a range of chemicals, with limonene being a key component. All citrus oils demonstrated powerful antioxidative activities. C. reticulata dried peel oil significantly inhibited collagenase and tyrosinase activities, resulting in promising anti-aging and whitening properties. C. reticulata oil derived from dried peels (CR3) had a higher yield and more potent activity than the oils taken from fresh leaves and peels. Therefore, CR3 was developed into a microemulsion in which the internal droplet size was 266.5 ± 14.1 nm and the narrowest PDI of 0.396 ± 0.068. Microemulsion could significantly reduce the skin irritation property of CR3 in human volunteers. In conclusion, CR3 microemulsion was suggested as effective and safe for further cosmeceutical applications.