Inhibitory effects of fruit extracts on nitric oxide-induced proliferation in MCF-7 cells Rajarajeswaran Jayakumar, M.S. Kanthimathi ⇑ Department of Molecular Medicine, Faculty of Medicine, University of Malaya, 50603 Kuala Lumpur, Malaysia article info Article history: Received 26 May 2010 Received in revised form 6 September 2010 Accepted 14 November 2010 Available online 24 November 2010 Keywords: Sodium nitroprusside Polyphenols Flavonoids Scavenging of nitric oxide abstract Nitric oxide is a free radical involved in the pathogenesis of cancer by increasing tumour vascularization and metastasis. Studies using nitric oxide inhibitors have shown decrease in tumour growth and a role in cancer therapy. To analyse the effect of fruits on nitric oxide, we carried out experiments using a nitric oxide donor on the breast cancer cell line, MCF-7. Proliferating MCF-7 cells were treated with the meth- anolic extract of the fruits. The inhibitory activity of fruit extracts on cell proliferation was measured using the MTT assay. Chiku and dragon fruit showed high inhibitory activity when compared to the other fruits tested. The total polyphenol and flavonoid content and nitric oxide scavenging activity were found to be high in pomegranate, chiku, litchi, durian, grape and apple. This study shows that phytochemicals present in fruits scavenge nitric oxide and inhibit MCF-7 cell proliferation. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction Free radicals are formed either by endogenous processes or exogenous exposures and are involved in the pathogenesis of chronic diseases like cancer, ageing and atherosclerosis (Halliwell, Gutteridge, & Cross, 1992). Nitric oxide is a simple, inorganic gas- eous free radical. It is an important signalling molecule synthesised during the conversion of L-arginine to citrulline by nitric oxide syn- thase (Knowles & Moncada, 1994). Nitric oxide increases tumour vascularization through angiogenesis which increases tumour growth and facilitates metastasis (Ng et al., 2007). Increased expression of nitric oxide synthase was observed in many human malignant tumors (Lin, Chen, Ye, & Zhu, 2003; Liu, Chan, & Mahen- dran, 2003; Vakkala et al., 2000). Inano and Onoda (2003) showed that nitric oxide derived from inducible nitric oxide synthase is in- volved in radiation-induced initiation of tumorigenesis. Inhibition of nitric oxide synthase using selective inhibitors resulted in the reduction of tumour growth (Thomsen & Miles, 1998). However, the nitric oxide inhibitors also had deleterious side effects. Lopez et al. (2004) showed that administration of the nitric oxide syn- thase inhibitor, 546C88, resulted in adverse effects, including, de- creased cardiac output, pulmonary hypertension, systemic arterial hypertension, heart failure and increased mortality in sep- tic shock patients. 7-Nitro indazole, an inhibitor of central nitric oxide synthase, induces depression, motor deficit and decrease in sleep stages (Dzoljic, de Vries, & van Leeuwen, 1996). N G -nitro-L- arginine methyl ester (L-NAME), an inhibitor of inducible nitric oxide synthase, dose dependently induced motor deficits in mice models (Araki et al., 2001). Fruits are rich in antioxidants such as flavonoids, anthocyanins, carotenoids, and vitamins (Duan, Jiang, Su, Zhang, & Shi, 2007; Her- nandez, Lobo, & Gonzalez, 2006). They exhibit antioxidant, anti- inflammatory, anti-cancer, anti-mutagenic, anti-carcinogenic and anti-bacterial properties (Bala & Grover, 1989; Bowen-Forbes, Zhang, & Nair, 2008; Negi, Jayaprakasha, & Jena, 2008; Omoni & Aluko, 2005). Epidemiological studies have shown that increased consumption of fruits is associated with a reduced risk of develop- ing cancer (Block, Patterson, & Subar, 1992). A study by Ahn et al. (2004) on breast cancer patients showed that the consumption of fruits has an inverse association with the risk of breast cancer. MCF-7, an oestrogen receptor-positive human breast cancer cell line, is commonly used in the analysis of anticancer activities of synthetic drugs, plant extracts and phytochemicals. In the present study we analysed the inhibitory effects of a number of fruits on nitric oxide-induced proliferation of MCF-7 cells. This further emphasises the benefit of consuming fruit to prevent and protect against cancer. Polyphenols present in the fruits contribute to can- cer inhibitory effects and are beneficial to human health. 2. Materials and methods 2.1. Fruits Thirteen varieties of commonly consumed fruits were pur- chased from the local market. They were chiku (Manilkara zapota), pomegranate (Punica granatum), mangosteen (Garcinia mangos- tana), kiwi fruit (Actinidia deliciosa), papaya (Carica papaya), star 0308-8146/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodchem.2010.11.093 ⇑ Corresponding author. Tel.: +60 3 79674913; fax: +60 3 79674957. E-mail address: kanthi@um.edu.my (M.S. Kanthimathi). Food Chemistry 126 (2011) 956–960 Contents lists available at ScienceDirect Food Chemistry journal homepage: www.elsevier.com/locate/foodchem