Stimulation of mouse melanocyte proliferation by Piper nigrum fruit extract and its main alkaloid, piperine

During a herbal screening programme to find potential repigmenting agents f or the treatment of vitiligo, Piper nigrum L. fruit (black pepper) extract was found to possess growth-stimulatory activity towards cultured melanocyt es. Its aqueous extract at 0.1 mg/ml was observed to cause nearly 300% stim ulation of the growth of a cultured mouse melanocyte line, melan-a, in 8 da ys (p < 0.01). Piperine (1-piperoylpiperidine), the main alkaloid from Pipe r nigrum fruit, also significantly stimulated melan-a cell growth. Both Pip er nigrum extract and piperine induced morphological alterations in melana cells, with more and longer dendrites observed. The augmentation of growth by piperine was effectively inhibited by RO-31-8220, a selective protein ki nase C (PKC) inhibitor, suggesting that PKC signalling is involved in its a ctivity. This is the first full report on such an activity of black pepper and piperine.