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 richness in polyphenols that act as anti‐aging molecules. Hibiscus roseus is a perennial species naturalized in Italy, with beautiful soft pink flowers; its phenolic composition and biological activities have not been studied yet. The aim of this study was to characterize and quantify the phenolics and to evaluate the antioxidant, sun protection factor (SPF), and anti‐collagenase activities of the ethanolic extracts of H. roseus leaves (HL) and flowers (HF). p‐Coumaric, chlorogenic, and trans‐ferulic acids derivatives as well as quercetin and kaempferol flavonoids were the main phenolic compounds detected. 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 phloridzin was 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. The SPF and anti‐collagenase activity of both extracts were similar and comparable to those of synthetic standards. The overall results demonstrate that H. roseus extracts are promising sources of bioactive phenolic compounds that could be potentially applied as anti‐aging agents in skin‐care cosmetics.