Valuable products from the flowers of lemon (Citrus limon (L.) Osbeck) and grapefruit (Citrus paradisi Macfad.) Italian trees

Citrus products are items of fundamental importance in the global market. The fruit of lemon (Citrus limon (L.) Osbeck) are mainly processed for the production of the juice, and of the peel essential oil, as a by-product. The same can be said for grapefruit (Citrus paradisi Macfad.), even if its production quantities are considerably lower. In the present study, the absolutes obtained from the flowers of Italian lemon and grapefruit plants were evaluated for their chemical composition and sensory properties. The GC analysis unveiled a volatile composition different from that of peel oils, being present compounds such as indole (0.04-0.22%) and methyl anthranilate (0.31-3.63%). The GC findings were correlated with sensory evaluation, carried out by a panel of trained assessors, that highlighted a pronounced floral character in grapefruit, while a predominant citrusy note was described in lemon. By means of an MDGC system, equipped with a chiral selector, a number of optical isomers were separated, allowing to define the enantiomeric ratios in these matrices for the first time. The nonvolatile fraction of the absolutes was investigated about its coumarin content by exploiting LC-UV and LC-MS methodologies. The predominant coumarins in grapefruit were epoxyaurapten (20,977.0 ± 300.1 mg L−1) and aurapten (3259.0 ± 68.4 mg L−1). A total amount of 9587.0 ± 210.6 mg L−1 was determined in lemon absolute, the highest content being that of bergamottin (2776.0 ± 65.5 mg L−1). The findings obtained in this study highlight the valuable properties of the absolutes of lemon and grapefruit flowers, as unique raw material for perfume and cosmetic industries.