Lipolytic effects of citrus peel oils and their components

This study was conducted to determine the lipolytic effects of eight kinds of citrus peel oils and their components. All of the citrus peel oils revealed lipolytic effects on olive oil model solution ranging from 10.9 to 73.8%. Hakyul (Citrus natsudaidai Hayata) showed the highest lipolytic effect (73.8%), followed by yuza (Citrus junos Sieb. ex Tanaka, 68.1%) and lemon (Citrus limonium, 63.4%), and their effects were comparable with or stronger than that of 5 mM raspberry ketone (p < 0.05). Among 17 authentic compounds relating to citrus peel oils, octanal (78.6%) showed the highest lipolytic effect, followed by gamma-terpinene (76.3%), limonene (75%), terpinen-4-ol (70.7%), nerol (69.9%), p-cymene (67.7%), and geranyl acetate (67.2%), and their effects were stronger than that of 5 mM raspberry ketone (p < 0.05). Ethyl acetate, alpha-pinene, myrcene, citronellal, linallyl acetate, and citronellol exhibited poor lipolytic effect in the model solution. Lipolytic effect was found to be high when the oils included a higher content of gamma-terpinene and p-cymene. Limonene showed potential lipolytic effect, and its effect is likely to be enhanced by the presence of gamma-terpinene and p-cymene. It is considered that monoterpene hydrocarbons consisting of one or two double bonds would have stronger lipolytic effect than those having three double bonds.