Sustainable Use of Chrysanthemum indicum var. aromaticum as Value-Added Green Materials in Microemulsion Hydrogels

The essential oil extracted from the flowers of Chrysanthemum indicum var. aromaticum (CIA) has excellent biological properties; however, the stems and leaves of CIA often get wasted. Maximizing the use of these wastes will help solve the sustainability issues of CIA resources. The present study analyzed the chemical compositions of CIA flower essential oil (CO) and stem and leaf extract (CE) by gas chromatography–mass spectrometry (GC–MS) and ultra-performance liquid chromatography–mass spectrometry (UPLC-MS). Then, the phytochemical properties, stability, antioxidant capacity, and cell (human L929) toxicity of CO and CE were further evaluated. Finally, oil-in-water microemulsion (ME) and hyaluronic acid hydrogel systems composed of CO and CE were developed to deliver bioactive ingredients effectively. The analysis identified 64 and 31 compounds in CO and CE, respectively, and indicated them as readily available sources of natural antioxidants, such as flavonoids and phenols. In addition, the formulation of the ME system (CIA-ME) improved CO stability and increased CE loading; these optimal formulations (ME, CIA-ME, CIA-ME gel) exhibited good stability, rheological properties, and sustained release properties without causing cell toxicity and skin irritation. The CIA-ME significantly inhibited intracellular tyrosinase activity and decreased intracellular melanin production in a dose-dependent manner. It also demonstrated skin photoprotection and inhibited tyrosinase, collagenase, and elastase activities. Overall, CIA as a plant raw material can serve as a promising topical cosmetic or medicine prototype. Applying CO and CE in combination provides a basis for the sustainable utilization of CIA resources.