An updated review of Cucurbitacins and their biological and pharmacological activities

Cucurbitacins (Cus) are a class of highly oxidized tetracyclic triterpenoids that confer a bitter taste to cucurbits such as cucumber, melon, watermelon, squash, and pumpkin. To date, a large number of Cus and Cu-derived compounds have been isolated from the Cucurbitaceae family and from other species of the plant (Alghasham, 2013; Shang et al., 2014). Cus have a range of biological and pharmacological activities that first attracted attention in the 1960s (Chen et al., 2012). Cucurbitacin B (CuB) and Cucurbitacin E (CuE) have been particularly widely studied (Lan et al., 2013). Recent reports have demonstrated that CuE has growth-inhibitory effects in the proliferation of many cancer cells such as bladder cancer, hepatocellular carcinoma, pancreatic cancer, breast cancer, and leukemia (Dong et al., 2010; Sörensen et al., 2012). CuB has been shown to have antimicrobial and anti-inflammatory activity. However, most reports on CuB focus on its anticancer activity. CuB inhibits the growth of human malignant cells, both in vitro and in vivo, and has been shown to be effective against breast cancer, head and neck squamous cell carcinoma, pancreatic cancer, hepatocellular carcinoma, osteosarcoma, and myeloid leukemia (Duangmano et al., 2010; Kausar et al., 2013; Guo et al., 2014a). Consequently, natural and semisynthetic Cus are proposed as a promising source for the development of new drugs for the prevention and treatment of various cancers. Here, we summarize key recent studies that have evaluated the biological and pharmacological activities of Cu and its derivatives (Table 1).