Dual Modulatory Effects of Phytochemicals from Iris ×germanica L. var. florentina Dykes Rhizome Extract on Melanogenesis

Abnormal skin pigmentation can cause significant esthetic concerns and impact quality of life. As melanin determines pigmentation, melanogenesis is a key target to manage pigmentation disorders. This study investigated the effects of extracts from the rhizome of <i>Iris ×germanica</i> L. var. <i>florentina</i> Dykes (often called <i>Iris florentina</i> L.) on melanogenesis. Active phytochemicals were identified by combining LC-MS-MS metabolic profiling with subsequent bioassay-directed fractionation of chromatographic eluent collected into 96-well plates. Fractions 41-43 increased melanin and contained germanaism B, providing evidence that it is a melanogenesis stimulator. In contrast, fractions 90-93 reduced melanin and contained iriflorental and iripallidal, identified as prospective melanogenesis inhibitors. To explore extract-based applications, the plant was subjected to ethanolic, chloroform, and supercritical carbon dioxide (SC-CO₂) extractions and tested in skin equivalent tissues. The ethanolic extract (rich in germanaism B) increased pigmentation, while the chloroform extract (higher in iriflorental and iripallidal) decreased it. The SC-CO₂ extract, with minimal germanaism B and enriched iriflorental and iripallidal, showed stronger depigmenting effect. This study is the first to report that rhizome of <i>I. florentina</i> contains phytochemicals with opposing effects on melanogenesis. Through different extraction processes, targeted extracts from a single botanical can address both hyper- and hypopigmentation, offering a novel approach to pigmentation modulation.