Lycopene in citrus fruit: biochemical mechanisms, molecular insights and health implications

Accumulation of the carotene lycopene in <i>Citrus</i> is an unusual trait found in a limited number of pummelos, grapefruits, oranges, lemons and related hybrids, imparting a distinctive pink-to-red color to the fruit. This phenotype most often arises from spontaneous bud-sport mutations and is generally confined to the inner fruit tissues (endocarp), although in some cultivars lycopene is also found in the rind (flavedo) or albedo. Pink-fleshed cultivars typically show an altered carotenoid profile, particularly in the pulp, with higher total carotenoid levels than their parental or standard counterparts. Comparative analyses across citrus species and cultivars reveal both shared and distinct patterns in carotenoid accumulation and tissue-specific pigmentation. The genetic and molecular bases of these changes are not yet fully resolved and appear to differ among species and cultivars. Beyond their scientific interest, these cultivars present promising opportunities for commercial development due to their striking coloration and provide enhanced nutritional value because of their high carotenoid levels. This review integrates and compares evidence from multiple citrus species and cultivars on the origin and diversity of lycopene-accumulating <i>Citrus</i>, their characteristic carotenoid composition, the proposed molecular and biochemical mechanisms leading to lycopene accumulation, and the nutritional and health implications of pink-fleshed cultivars.