Melanotan and Melanotan 2 are both analogues of the peptide hormone alpha-melanocyte stimulating hormone (α-MSH) that tend to induce skin tanning. Unlike Melanotan 1, Melanotan 2 has been shown to have aphrodisiac properties, the additional effect of increasing libido. Melanotan 2 is a cyclic heptapeptide analogue of the alpha-melanocyte stimulating hormone (a-MSH).

The effects of Melanotan 2 on laboratory mice have demonstrated that the central melanocortin (MC) has been activated by melanotan 2 when fed and induced in the mice. The six-day treatment of Melanotan 2 has shown that the peptide actually reduced the body weight and the adipose tissue in the viscera of the mice and suppressed the caloric intake of the organism. This has implications for clinical applications of the possible treatment to reduce carbohydrate or calorie intake, especially for the overweight and the obese. Furthermore, the same study has also demonstrated that there was a sustained increase in the available oxygen consumption in obese animals. Melanotan 2 also helped reduce the level of serum insulin and cholesterol levels when compared with the control treatments. Furthermore, it has been suggested that melanotan 2 actually lowers the level of acetylcholine A carboxylase expression and even prevents the reduction of carnitine and palmitoyltransferase I mRNA in muscle-type tissues by pair-feeding in the muscles of obese rats. Moreover, the Melanotan 2 peptide actually increased the fat catabolism in the muscles and even improved the cholesterol metabolism (Li et al. 2004).

Melanotan 2 peptide was originally developed as a defence against the potential cancer-causing effects of the sun’s ultraviolet radiation through its action of stimulating natural melanin production in the absence of sunlight, which allows for the sunless darkening of skin tone.