Indian Journal of Experimental Biology Vol. 53, November 2015, pp. 753-761 Grapevine fruit extract protects against radiation-induced oxidative stress and apoptosis in human lymphocyte Indrani Singha & Subir Kumar Das* Department of Biochemistry, College of Medicine & JNM Hospital, WBUHS, Kalyani, Nadia-741 235, West Bengal, India Received 15 April 2015; Revised 31 May 2015 Ionizing radiation (IR) causes oxidative stress through overwhelming generation of reactive oxygen species (ROS) in the living cells leading the oxidative damage further to biomolecules. Grapevine (Vitis vinifera L.) posses several bioactive phytochemicals and is the richest source of antioxidants. In this study, we investigated V. vinifera for its phytochemical content, enzymes profile and, ROS- and oxidant-scavenging activities. We have also studied the fruit extract of four different grapevine viz., Thompson seedless, Flame seedless, Kishmish chorni and Red globe for their radioprotective actions in human lymphocytes. The activities of ascorbic acid oxidase and catalase significantly (P <0.01) differed among extracts within the same cultivar, while that of peroxidase and polyphenol oxidase did not differ significantly. The superoxide radical-scavenging activity was higher in the seed as compared to the skin or pulp of the same cultivar. Pretreatment with grape extracts attenuated the oxidative stress induced by 4 Gy γ-radiation in human lymphocytes in vitro. Further, γ-radiation-induced increase in caspase 3/7 activity was significantly attenuated by grape extracts. These results suggest that grape extract serve as a potential source of natural antioxidants against the IR-induced oxidative stress and also inhibit apoptosis. Furthermore, the protective action of grape depends on the source of extract (seed, skin or pulp) and type of the cultivars. Keywords: Antioxidants, Caspase 3/7, Ionizing radiation, Polyphenols, Radioprotective agents, ROS, Vitis vinifera. Ionizing radiation (IR) is widely used in modern medicine for diagnostic and therapeutic purposes, including cancer treatment 1-3 . Increased utilization of γ-radiation for medical and industrial purposes has lead to increased radiation hazards in humans. In radiotherapy of cancer, normal cells are also damaged during the exposure γ-radiation 3 . Radiation hazards are mainly manifested by radiolysis of body water 4 . Low Linear Energy Transfer (LET) radiations act by generating the free radicals 5 . These free radicals interact with different components of the cells including cell membrane and different intracellular molecules like DNA, RNA and proteins, resulting in cellular dysfunction and mortality 5-7 . Subcellular membranes, in view of their high content of polyunsaturated fatty acids, are major targets of oxidative damage and their adverse alterations can lead to undesirable consequences 8 . IR induces the production of reactive oxygen species (ROS) and promotes changes in the expression of several apoptotic proteins, leading to elevated apoptosis 9 . Therefore, it is crucial to identify an effective radioprotective agent capable of protecting against the radiation-induced cell death by scavenging the free radicals. Although several synthetic compounds have been found to be good radioprotectors, their practical application remains limited due to the high systemic toxicity at their optimum protective dose 4 , which accentuated the search for either less or non-toxic radioprotective compounds of biological origin. Plants rich in antioxidants and minimally toxic in nature are known for use in amelioration of the damage caused by oxidative stress 6,7,10 . Flavonoids, a family of natural products present in many fruits, vegetables, and beverages, exhibit pharmacological properties including the anti-inflammatory, hepatoprotective, and antioxidant actions 11-14 . These natural products of plant origin also react with and scavenge free radicals and reactive molecules produced by oxidative stress. These interactions are facilitated by their polyphenol ring structure with hydroxyl and methoxyl groups, or both that can specifically bind to or react with a base or other groups in the DNA backbone, as well as trap or scavenge the ROS. These polyphenolic compounds considerably mitigate the damaging effects of ionizing —————— *Correspondence: Phone: +91 33 2582 8562 E-mail: drsubirkdas@gmail.com