Utilization of Gardenia jasminoides discarded leaves as agricultural by-products in nanoemulsions for cosmetic industry: Enhancing stability, controlled release, and prolonged skin retention

In the perfume industry, Gardenia jasminoides cultivation primarily focuses on the flowers, leading to the routine disposal of its leaves as agricultural waste. Therefore, this study aimed to evaluate the potential of G. jasminoides leaves for cosmeceutical applications and to develop a nanoemulsion. The leaves were extracted with ethanol using conventional maceration (three cycles of 24 h), maceration with continuous shaking (30 min), and ultrasonication for 30 min (ULT). The extracts were analyzed for their chemical constituents, including phenolics, flavonoids, and rutin. Their biological activities relevant to cosmeceutical applications, including antioxidant, anti-hyaluronidase, and anti-collagenase effects, were tested through in vitro assays. Their safety profiles, including irritation and cytotoxicity, were assessed. The most effective extract was incorporated into the optimized nanoemulsion of Calophyllum inophyllum oil and evaluated for the stability, release profile, and skin retention. ULT yielded the highest flavonoid and rutin content, exhibiting the most potent antioxidant (IC 50 = 33.2 ± 8.6 µg/mL) and anti-hyaluronidase activities (IC 50 = 66.6 ± 8.2 µg/mL), along with no irritation or cytotoxicity. After incorporation into the nanoemulsion, the droplet size was 182.2 ± 0.3 nm, with a narrow polydispersity index and a pronounced zeta potential. The nanoemulsion demonstrated enhanced phytochemical stability, controlled release, and prolonged skin retention compared to the aqueous solution. As rutin was released steadily over 12 h, this suggested its potential for prolonged dermal efficacy. These findings supported the use of ULT as a promising bioactive ingredient for cosmeceutical applications, with the nanoemulsion formulation enhancing its stability, release profile, and skin retention. Additionally, this study is the first to utilize G. jasminoides leaves in a cosmetic nanoemulsion, demonstrating practical implications for cosmetic applications. Future safety and efficacy evaluations in human volunteers would be warranted to translate these findings into practical cosmeceutical applications. • Gardenia jasminoides leaf by-product was beneficial for cosmeceutical applications • G. jasminoides extract showed strong antioxidant and anti-hyaluronidase activities • Nanoemulsion improved stability, controlled release, and prolonged skin retention