Vitamin E isomers and cancer research: A review

Each year, thousands of new cancer cases are reported all over the world. Among them, breast, colorectum, lung, nasopharynx and liver cancers are the top 5 cancer cases reported in 2018 in Malaysia (World Health Organization, 2020). In the same year, lung, colorectum, breast, liver and leukaemia cancer were the major death cancer cases in Malaysia. Radiotherapy, chemotherapy, and surgery are commonly used to treat cancer. However, they may cause some serious side effects apart from the common effects such as nausea and vomiting. Thus, more studies were done to search for alternative cancer treatments to reduce or eliminate these side effects. Vitamin E (tocopherol and tocotrienol) is one of the natural ingredients that were studied recently, and the compound was reported to show an anticancer properties. Tocopherol and tocotrienol were further divided into α-, β-, γ- and δ-tocopherol and tocotrienol but not all isomers were extensively studied. Most studies focusing on the examined isomers were in vitro investigations, with a few extending to in vivo studies. Only a few studies have progressed to clinical studies. This review aims to provide comprehensive information of previous studies on isoforms of vitamin E towards cancer studies.