## 4 Discussion
The excessive production of ROS in normal cells leads to the initiation of DNA damage and carcinogenesis [1; 5; 46; 47]. Many plants have been reported to possess the antioxidant properties to decrease the ROS level in cancer cells [48; 49; 50]. Low ROS level plays an important part in cellular signaling, cell proliferation, and apoptosis [1; 51]. Moreover, cells have mechanisms to repair damaged DNA. However, if the damaged DNA cannot be repaired, cells will undergo apoptotic cell death. DNA damage-induced apoptosis is a cellular defense mechanism to eliminate genetically damaged cells [52; 53]. Apoptosis induction is, therefore, an endpoint for screening anticancer action [54; 55]. Our study found that BGR induced apoptosis in Jurkat cells at 24 h. During apoptosis, DNA is condensed and fragmented, and there is an externalization of phosphatidylserine to the outer side of the cell membrane of apoptotic cells. Later, phagocyte molecules involve in recognition and remove unrepairable apoptotic cells without triggering inflammation [55]. The flipping of phosphatidylserine can specifically bind with annexin V that can be detected by flow cytometry to indicate the early stage of apoptosis [55]. The cytotoxic effect of BGR occurred via apoptosis as the Jurkat treated cells were stained with annexin V. Moreover, caspase 3/7, that is the downstream effector caspases in the caspase cascade pathway [56], was increased in the BGR-treated Jurkat cells. Our results indicated that BGR induced an early stage of apoptosis detected by cells stained with annexin V measuring by flow cytometry and induced Jurkat cells to die via apoptotic death mode as observed from the increasing of caspase 3/7 activity. A previous study also reported that the fermented mixture of brown rice and rice bran induced apoptosis in human acute lymphoblastic leukemia cells [57], which is in agreement with our study. Several studies reported the contribution of plant phenolic content to antioxidant, cytotoxicity, and apoptosis in cancer cell lines [58; 59] as well as anthocyanin, one of the flavonoidgroups, for its cancer prevention activity [60; 61]. Hence, the phenolic content and anthocyanin content of BGR may contribute to its antioxidant, cytotoxicity, and apoptosis in the Jurkat cells. It should be noted that rice sprout is a young green leaf where the second metabolites or active compounds are synthesized after photosynthesis. The difference in the types and contents of compounds in the same plant found between studies could be affected by several factors such as different harvest time, age, parts, growing condition, and the type of solvent used for the extraction. The previous study extracted the rice sprout (20 g) with 1% hydrochloric acid in methanol (100 mL) twice each by sonication for 30 min [24]. Our study extracted the rice sprout (20 g) with 1% hydrochloric acid in methanol 1000 mL and sonicated for 30 min. A previous study of BGR and RD6 at the same harvest ages reported the existence of important phytochemicals, including total chlorophyll content (TCC), total flavonoid content (TFC), total phenolic content (TPC), total anthocyanin content (TAC), and the proximate composition (i.e., ash, moisture, fat, protein, carbohydrate, energy, and dietary fiber content) [24]. Moreover, protocatechuic acid, vanillic acid, and rutin were quantified in a different amount in BGR and RD6 [24]. The BGR and RD6 rice sprout used in the previous and the present study were at the same harvest age and grown under the same condition but extracted with a slightly different method. Moreover, the extract from BGR and RD6 could comprise of other phytoconstituents besides these identified compounds. The content of protocatechuic acid, vanillic acid, and rutin was not re-analyzed in the present study. Instead, the marker compounds--TPC and TAC--were quantified in the extract, as they reportedly attribute to antioxidant, antiproliferative, and apoptosis induction effects in other plants of other studies.