Citral or dimethyl octadien al is a mixture
Citral or 3,7-dimethyl-2,6-octadien-1-al is a mixture of two stereoisomeric monoterpene aldehydes (the trans isomer geranial, citral A (40–62%)) and the cis isomer neral, citral B (25–38%) and serves one of the main constituent of essential oils of C. citratusis used in cosmetic, food, fungicides, perfumery and pharmaceuticals.Citral is also found in essential oils of several plants,such as Melissa, lemon, etc. In MCF-7 cells, citral (IC50, 180μM) inhibited the breast cancer cells growth,induced apoptosis, arrested the Superoxide Dismutase (SOD) Activity Assay Kit mg arrest at G2/M phase and reduced prostaglandin E2 level . Additionally, C. citratus essential oil for 24h (IC50 200μg/mL) reduced the growth of HeLa and ME-180 cells while citral suppressed the cell proliferation (IC50 of 300 and 500μg/mL, respectively) and promoted apoptosis through the increased production in intracellular ROS and dissipation of MMP in HeLa and ME-180 cells . Citral at concentration of 44.5μg/mL was reported to induce apoptotic activity in hematopoietic cancer cell lines through the activation of caspase-3 and DNA fragmentation in BS-24-1, JURKAT and U937 cells . Recently, citral was shown to inhibit the proliferation of pancreatic cell tumor lines (MIA PaCa-2 cells) and human B-lymphoma (DeFew cells) . Citral from Verbena officinalis essential oil at lower concentration was shown to induced higher apoptosis that is thought to be via procaspase-3 activation in lymphocytes collected patients with chronic lymphocytic leukemia as compared to normal blood donors . In another study, citral induced apoptosis in acute promyelocytic leukemia NB4 cells via mitochondrial-mediated apoptosis and inactivation NF-κB in dose- and time-dependent manner . Citral was also reported to inhibit the proliferation of p53-expressing ECC-1 and OVCAR-3 cells and p53-deficient SKOV-3 cells by inducing G1/S cell cycle arrest and apoptosis via modulation of Bax and Bcl-2 expression and activation of cleaved caspase-3 . Furthermore, citral promoted endoplasmic reticulum (ER) stress in SKOV-3 cells by increasing the ER stress markers CHOP, GADD45, EDEM, ATF4, Hsp90, ATG5, and phospho-eIF2α.Citral in combination with curcumin synergistically induced arrestment of cell cycle at G0/G1 phase and apoptosis via elevation of ROS, activation of p53 and poly (ADP-ribose) polymerase-1 in MCF 7 and MDA MB 231 cell without affecting normal breast cells, MCF 10A . The co-treatment of retinoic acid and citral (3.12/5–12.5/20μg/mL) was shown to induce apoptosis and modulate G1 phase by upregulating cyclin D and p21 and downregulating cyclin A in A549 cells . The promotion of apoptosis in cancer cells has been the main therapeutic approach for treatment of various cancers , . Cellular apoptosis can be induced via two major pathways which are the death receptor (extrinsic) pathway and the mitochondrial (intrinsic) pathway that ultimately lead to the cascade caspases activation that are responsible to execute apoptosis through proteolytic cleavage of proteins . Additionally, p53, a 53kD nuclear phosphoprotein is a tumor suppressor protein that is encoded by the TP53 gene in human has been reported to play a cardinal role in cellular stress responses pathways that includes cell cycle arrest, senescence, inhibition of cell proliferation and apoptosis ,  The p53 is known to enhance cellular apoptosis by targeting Bax activation which then shift the balance between the anti- and proapoptotic proteins , . Furthermore, the elevation of intracellular ROS is known to induce the activation of p53 that is sensitive towards cellular redox change and ultimately, leads to apoptosis ,  In the present study, we demonstrated that citral inhibited the growth of HCT116 and HT29 colorectal cancer cell lines by activating p53 and inducing ROS-mitochondrial-mediated apoptosis through the modulation of Bax, Bcl-2 and Bcl-xL expression and concomitant activation of caspase-3.