Cytotoxic Effects of Essential Oils of Some Iranian Citrus Peels

There have been efforts to overcome the problem in treatment of cancer using medicinal plants. It has been shown that Citrus essential oil of contains different terpens with antitumor activities. In this study we sought to determine the cytotoxicity of essential oils of Iranian Citrus limon (L.), C. medica (L.), C. sinsensis (L.) peels on cancer cell lines. Essential oils were prepared by hydrodistilation and characterized by GC-MS. The effects of C. limon (5-40 µg/ml), C. medica and C. sinensis (0.25-10 µg/ml) on two human tumor cell lines (MCF-7 and Hela) were determined. Different concentrations of essential oils were added to cultured cells and incubated for 72 h. Cell survival was evaluated using the MTT-based cytotoxicity assay. While limonene comprise about 98.4% and 98.8% of content of C. limon and C. sinensis essential oils respectively, its’ percentage in C. medica was only 56.6%. In C. medica there was a considerable amount of β-pinene, γ-terpinene, α-terpinolene and trans-α-bergamotene. IC₅₀ of essential oil for MCF-7 cell line was: C. limon ≈ 10 µg/ml, C. medica ≈ 1 µg/ml and C. sinensis ≈ 0.5 µg/ml. For Hela cell line IC₅₀ was: C. limon ≈ 17 µg/ml, C. medica ≈ 1 µg/ml and C. sinensis ≈ 3 µg/ml. Our findings revealed that C. limon and C. sinensis had a greater cytotoxic effect on MCF-7 than that on Hela cells. Also, comparing IC₅₀, our findings indicated that C. medica and C. sinensis were more cytotoxic than C. limon. Comparison of the essential oil component of C. limon with C. medica, shows the presence of β-pinene (16.3%), α-terpineol (11.3%), γ-terpinene (4.4%), and trans- α-bergamotene (3.4%), which were not found in C. limon. Hence, it could be concluded that these components may have greater cytotoxic effects or they may also have synergistic effects with limonene.