Cytotoxic activity and volatile components of peel oil of Citrus volkameriana

Abstract

Citrus volkameriana Pasq. (Family: Rutacea) is a very common edible and medicinal plant growing in several places in the world including Egypt. We previously studied the toxicity of components of the leaves; however, the peel oil has not been fully analyzed. In the current study, peel oil of C. volkameriana was prepared by hydro-distillation method, and was analyzed for its components using gas chromatography and gas chromatography–mass spectrometry. The recovered oil was formulated as oil in water emulsion using a wet gum technique with gum acacia as an emulsifier. Two compounds were selected from the identified oil components, emulsified using the same technique, and tested for their cytotoxicity along with the emulsified oil on five human tumor cell lines, as well as on one human non-tumorigenic epithelial breast cell line. Our results showed that limonene (68.5%) was found to be the major oil constituent, followed by γ-terpinene (11.3%). Other minor oil components include thymol methyl ether (4%), 4-terpineol (2.9%), cymol (2.4%) and α-pinene (2.1%). The oil showed a very strong cytotoxic effect on the five human tumor cells tested with the highest effect on human hepatoma HepG2 cells (IC50 = 0.038 μL/mL), followed by the effect on human laryngeal carcinoma HEp2 cells (IC50 = 0.045 μL/mL), human breast adenocarcinoma MCF7 cells (IC50 = 0.075 μL/mL), human lung carcinoma A549 cells (IC50 = 0.093 μL/mL), and human cervical cancer Hela cells (IC50 = 0.13 μL/mL). In contrast, the oil showed a lower cytotoxic effect on the non-tumorigenic breast MCF10A cells (IC50 = 0.106 μL/mL). D-limonene possessed similar cytotoxic results as the oil, suggesting a vital role in the cytotoxic effect obtained with the oil. Furthermore, α-pinene showed a strong cytotoxic effect on MCF7 cells (IC50 = 0.072 μL/mL) with a weaker effect on the MCF10A cells (IC50 = 0.185 μL/mL). In conclusion, Citrus volkameriana peel oil and its components have the potential to act as promising cytotoxic agents.