Antioxidant Capacity, Cytotoxicity, and Acute Oral Toxicity of Gynura bicolor

Gynura bicolor (Compositae) which is widely used by the locals as natural remedies in folk medicine has limited scientific studies to ensure its efficacy and nontoxicity. The current study reports the total phenolic content, antioxidant capacity, cytotoxicity, and acute oral toxicity of crude methanol and its fractionated extracts (hexane, ethyl acetate, and water) of G. bicolor leaves. Five human colon cancer cell lines (HT-29, HCT-15, SW480, Caco-2, and HCT 116), one human breast adenocarcinoma cell line (MCF7), and one human normal colon cell line (CCD-18Co) were used to evaluate the cytotoxicity of G. bicolor. The present findings had clearly demonstrated that ethyl acetate extract of G. bicolor with the highest total phenolic content among the extracts showed the strongest antioxidant activity (DPPH radical scavenging assay and metal chelating assay), possessed cytotoxicity, and induced apoptotic and necrotic cell death, especially towards the HCT 116 and HCT-15 colon cancer cells. The acute oral toxicity study indicated that methanol extract of G. bicolor has negligible level of toxicity when administered orally and has been regarded as safe in experimental rats. The findings of the current study clearly established the chemoprevention potential of G. bicolor and thus provide scientific validation on the therapeutic claims of G. bicolor. 1. Introduction Plants have been used to maintain human health for a very long time. It is well known that some of the plant species possess interesting bioactivities with potential therapeutic applications which can benefit us. Gynura bicolor, locally known as “Hong Feng Cai” (Chinese) and “Sambung Nyawa Ungu” (Malay), belongs to the botanical family of Compositae. The leaves of G. bicolor distinctively show reddish purple color on the abaxial side and green color on the adaxial side. The native geographic distribution of G. bicolor occurs in China, Taiwan, Myanmar, and Thailand. The G. bicolor is consumed as a culinary cooked vegetable and believed to confer a wide range of benefits such as anticancer, anti-inflammatory, and possibly antihypertensive effects. G. bicolor is also used for post-labor recovery, blood circulation improvement, treatment of dysmenorrhea, hemoptysis, and diabetes by the locals [1–3]. Although G. bicolor is widely used in Malaysia, there are no recorded data of locally grown G. bicolor species. Scientific studies on the use of locally grown G. bicolor to ensure its efficacy and nontoxicity have not been carried out. Several phytochemical and biological reports showed that G. bicolor