**Abstract**

The WHO says that annual cases of cancer will increase from 14 million in 2012 to 22 million in the next two decades. Cancer is the second cause of death in the world; in 2015, it caused 8.8 million deaths. On the other hand, it is necessary to consider that 70% of the total deaths due to this disease occur in developing countries, who have the least resources to acquire the drugs of choice for the treatment of this disease. Although there are treatments and these are effective, there are currently cases of resistance to drugs used to treat this disease, which has led to the search for new sources of drugs or compounds effective against the cancer being active; plants are the possible sources to achieve this. Cucurbitaceae is a family of plants widely distributed on the planet which has been used traditionally for the treatment of this disease and from they have been isolated different cucurbitanes. These compounds possess a wide biological activity, antidiabetic, anti-inflammatory, hepatoprotective, or cytotoxic and antitumoral effects. The aim of this review is to present 51 cucurbitacin compounds and 2 with different structures isolated from Cucurbitaceae plants with cytotoxic or antitumoral activity.

**Keywords:** cucurbitacin, Cucurbitaceae, cytotoxic, cancer, natural product

## **1. Introduction**

Cancer is an abnormal growth of cells, which begin to divide without stopping and can form solid tumors. Cancer is a collection of more than 100 different diseases with genetic changes, which can be inherited or be caused by environmental exposure to chemicals, tobacco smoke, or radiation, such as UV rays from the sun.

Cancer is the second leading cause of death in the US and is responsible for approximately 1 out of every 4 deaths. Globally, nearly 1 in 6 deaths is due to cancer. Approximately, 70% of deaths from cancer occur in low- and middle-income countries. There were 14.1 million new cancer cases, 8.2 million cancer deaths, and 32.6 million people living with cancer (within 5 years of diagnosis) in 2012 worldwide, based on World Health Organization (WHO) estimates. A total of 57% (8 million) of new cancer cases, 65% (5.3 million) of cancer deaths, and 48% (15.6 million) of 5-year prevalent cancer cases occurred in less-developed regions [1, 2].

#### *Pharmacognosy - Medicinal Plants*

The most common treatments for cancer are surgery, chemotherapy, and radiation therapy, and in many cases, they are used in combination [3]. These treatments can be effective but can cause side effects, such as anemia, appetite loss, fatigue, and alopecia [4].

### **1.1 Generalities of the Cucurbitaceae family**

 Plants are an important source of compounds currently used in cancer chemotherapy. The Cucurbitaceae family, also called cucurbits, contains 120 genera with 825 species that are widely distributed in tropical and temperate regions [5], and those with edible fruits were the first cultivated plants in Europe and America. Many species of the Cucurbitaceae family are used as human food [6]. Most of the species in this family are annual vines, and some are lianas, thorny shrubs, or trees. The most important genera of this family are *Cucurbita* (squash, pumpkin, zucchini), *Lagenaria* (calabash), *Citrullus* (watermelon), *Cucumis* (cucumber, various melons), and *Luffa* (luffa).

### **1.2 Cucurbitanes of the Cucurbitaceae family with cytotoxic effects**

Some cucurbitanes have been isolated from different species of the Cucurbitaceae family. These compounds exhibit an extensive range of biological actions, specifically antidiabetic, anti-inflammatory, cytotoxic, hepatoprotective, cardiovascular, and antiparasitic effects [7].

Cucurbitacins are characteristic compounds in many species of cucurbits. These compounds are tetracyclic triterpenes arising from a rearrangement of the protostane cation and are unsaturated and polyfunctional oxygenated compounds and occur most often as glycosides. They are particularly toxic and bitter chemicals, and their cytotoxicity contributes to their toxicity [8]. Cucurbitanes are found in many plants.

The most significant mechanisms of the apoptotic effects of cucurbitacins are their ability to modify the mitochondrial transmembrane potential and transcriptional activity via nuclear factors or genes and their ability to activate or inhibit pro- or antiapoptotic proteins.

Similar to other plant-derived compounds, cucurbitacins exert toxic effects in different cancer cell lines by inducing apoptosis. The main mechanism of this induction is the ability to modify the mitochondrial transmembrane potential [6].

Therefore, some compounds obtained from Cucurbitaceae could be useful scaffolds for developing new drugs. We consider it necessary to review the main chemicals from this genus with potential anticancer activity.

#### **2. Cucurbitacins tetracyclic triterpenoids**

 Cucurbitacins are primarily tetracyclic triterpenoids (**Figure 1**) that compose a class of biochemical compounds contained in plants of the family Cucurbitaceae, which include the Thai medicinal plants *Trichosanthes cucumerina* L. and *T. kirilowii*  Maximowicz, the leaves and fruits of the Tunisian plant *Ecballium elaterium*; the fruits of *Cucurbita pepo* cv. dayangua; the roots of *Cayaponia tayuya* (Tayuya), which has long been used in folk medicines from Brazil, Peru, and Colombia; *C. racemosa*  Cong., the roots of *Hemsleya amabilis*, an ancient Chinese remedy, *Cucumis melo* L., *Momordica balsamina* L. (balsam pear), *Cucurbita andreana* (winter squash), and *Citrullus colocynthis* (bitter cucumber). Below, the most important cucurbitacins that have shown interesting cytotoxicity and anticancer activity are listed.

*Cytotoxic and Antitumoral Activities of Compounds Isolated from Cucurbitaceae Plants DOI: http://dx.doi.org/10.5772/intechopen.82213* 

#### **Figure 1.**

*General structure of cucurbitacin tetracyclic triterpenoid.* 
