Phenolic Compounds from Leaves and Flowers of Hibiscus roseus: Potential Skin Cosmetic Applications of an Under-Investigated Species

The use of plant extracts in skin-care cosmetics is a modern trend due to their richnessin polyphenols that act as anti-aging molecules. Hibiscus roseus is a perennial species naturalizedin Italy, with beautiful soft pink flowers; its phenolic composition and biological activities havenot been studied yet. The aim of this study was to characterize and quantify the phenolics and toevaluate the antioxidant, sun protection factor (SPF), and anti-collagenase activities of the ethanolicextracts of H. roseus leaves (HL) and flowers (HF). p-Coumaric, chlorogenic, and trans-ferulic acidsderivatives as well as quercetin and kaempferol flavonoids were the main phenolic compoundsdetected. Catechin, epicatechin, kaempferol-3-O-rutinoside, kaempferol-3-O-glucoside, kaempferol-7-O-glucoside, tiliroside, oenin, and peonidin-3-O-glucoside were detected only in HF, while phloridzinwas exclusive from HL, which also showed greater amounts of hydroxycinnamic acid derivatives.HF was richer in flavonoids and total phenolics, also exhibiting greater antioxidant capacity. TheSPF and anti-collagenase activity of both extracts were similar and comparable to those of syntheticstandards. The overall results demonstrate that H. roseus extracts are promising sources of bioactivephenolic compounds that could be potentially applied as anti-aging agents in skin-care cosmetics.