Raw polysaccharides, previously described in detail, were isolated from the flowers of Hibiscus sabdariffa L. and fractionated by ion exchange chromatography into one neutral and three acidic subfractions. Raw polysaccharides and all acidic subfractions caused a strong induction of proliferation of human keratinocytes (HaCaT) of up to 40 %, while the neutral polymers were ineffective. While mitochondrial activity was not influenced, raw polysaccharides induced early differentiation of primary natural human keratinocytes, as determined by involucrin formation.