Chemical composition and cytotoxicity of Philippine calamansi essential oil

Abstract

The development of drug resistance is widespread in today's arsenal of chemotherapeutic agents and this has brought renewed interest in the use of natural products. Calamansi (Citrus microcarpa B.) is an essential oil-rich citrus from the Philippines popularly used in beverages and condiments. Calamansi wastes from processing plants are underutilized and may pose environmental concerns if not properly processed. This study aims to determine the volatile composition, d-limonene content, and cytotoxicity of calamansi essential oil. The calamansi essential oil was prepared by steam distillation and characterized using Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy and Gas Chromatography analysis. Cytotoxicity on human mammary tumor cell line MCF-7 and Chinese hamster ovary non-tumor cell line AA8 were assessed by MTT assay. Gas Chromatography-Mass Spectrometry qualitative analysis results revealed that d-limonene is the major constituent of calamansi essential oil comprising at least 92.67% of the total oil. Quantification of d-limonene in essential oil using a reference standard by Gas Chromatography-Flame Ionization Detector has shown 98.1% w/w. The IC50 of calamansi essential oil on MCF-7 and AA8 cells were identified to be 7.98 ± 1.77 and 16.15 ± 8.35 μg/mL respectively. Our findings suggest that calamansi essential oil has greater cytotoxic activity on MCF-7 than AA8 and this activity can be directly attributed to the high amount of d-limonene and perhaps the presence of other terpenes that may also have synergistic effects with d-limonene. Calamansi essential oil can be a good candidate for a natural low-cost chemopreventive and chemotherapeutic agent. These findings are of considerable economic interest to Philippine calamansi industry which produces large amount of calamansi pericarp waste.