Radical scavenging and cytotoxicity evaluation of eight extracts of <i>Citrus limon</i> and <i>Citrus aurantifolia</i>

Abstract

Cancer is a global cause of death characterized by uncontrolled proliferation and spread of abnormal cells. Eight extracts composed of the leaf, stem bark, seeds and juice of each of Citrus limon and C. aurantifolia were subjected to in vitro antioxidant assay using DPPH, brine shrimp lethality bioassay (BSL) and cytotoxicity MTT colorimetric assay using human cancer cell lines. Extracts of C. aurantifolia stem bark and leaf had IC₅₀ of 28.2±0.11 and 47.2±0.39μg/mL, respectively and displayed better radical scavenging activity compared to the other extracts, Ascorbic acid, the reference drug, had an IC₅₀ of 9.2±0.14 μg/mL. Citrus limon stem bark (LC₅₀=10.0±0.33) and C. limon leaf (LC₅₀= 5.0±0.74 μg/mL) extracts were observed to be strongly cytotoxic compared to cyclophosphamide (LC₅₀=98.76±0.15 μg/mL), while the other extracts were either non, weakly, or moderately toxic in BSL assay. Citrus aurantifolia leaf extract (CC₅₀=4.02±2.85 μg/mL, CC₅₀=5.45±2.8 μg/mL) retained a comparable cytotoxicity to cyclophosphamide (CC₅₀=2.23±0.14 μg/ mL, CC₅₀=2.66±0.8 μg/mL) on Rd and Hep-2c human cancer cell lines, respectively. The other extracts exhibited varying degrees of cytotoxicity. This study demonstrated that the extracts of both Citrus species had weak DPPH radical scavenging activity. Citrus aurantifolia leaf extract displayed potent toxicity in BSL assay and on the two human cancer cell lines; Rd and Hep-2c used in the study and were selective to cancer cells than the normal cell, Vero.

Keywords: Citrus limon, Citrus aurantifolia, DPPH Antioxidant, Brine Shrimp Lethality, Human cancer cell lines