This invention relates to novel compounds with skin lightening properties based on an aromatic hydrazine carboxyimidoamide structure, topical skin lightening compositions comprising the same and a method of skin lightening using the said compositions. In particular, the skin lightening benefit is selected from any one of the group consisting of treating melasma, treating post-inflammatory hyperpigmentation, treating age spots, treating dark spots and treating uneven skin tone.Desired skin colour is a major unmet consumer need around the world and especially in Asia. Consumers particularly desire even skin colour, absence of age spots (solar lentigines), absence of hyperpigmentation and lighter overall skin tone. One solution is to use biological actives that reduce the activity of melanocyte cells in skin. These cells, present in the basal layer of the epidermis, make the dark coloured pigment melanin and export it, in small export vesicles called melanosomes, to the neighbouring keratinocytes. It is well described in the literature that compounds which reduce melanin synthesis when topically applied to the skin will reduce skin darkness over time and can generate a more even skin tone.Tyrosinase is a very popular target for the regulation of melanocyte pigment production. However effective inhibitors of tyrosinase are bedevilled by safety issues causing, for example, melanocyte cell death, permanent depigmentation, irritation and allergic reactions. Often effective inhibitors kill melanocytes (for example hydroquinone) or cause sensitisation reactions. There is therefore a great need for safe and effective inhibitors of skin pigment production that work through an alternative safe mechanism.The inventors have observed that selected compounds of the same generic structure inhibit the production of soluble melanin by B16 mouse melanoma cells without cell toxicity.
