## 1 Introduction
From products of plant origin, the extraction of elements of interest is achieved so that they can be applied against neoplastic cells, either in isolation or when looking for a possible improvement of their antitumor activity when they are transported in nanoparticles (NPs). For this reason, numerous preclinical studies are being carried out to verify the possible chemopre and therapeutic effect of these elements, with the aim of incorporating them as adjuvants to treatments with current scientific evidence to increase the beneficial effect on patients [14]. Among the various groups of natural products with anticarcinogenic action are polyphenols, terpenoids, cardiac glycosides, saponins, flavonoids and others [15]. One of the most studied groups that stand out for their bioactivity are polyphenols, which are chemical substances found in fruits, cereals and vegetables that have anti-inflammatory and anticarcinogenic activities (Figure 1) [16]. Within them, we can distinguish flavonoids, flavanes, flavonoids and flavanones [15; 17]. Cardiac glycosides have also been shown to be useful as anti-arrhythmic agents and are beneficial for heart failure, increasing cardiac contraction by inhibiting the sodium-potassium ATPase pump [15; 18]. Furthermore, terpenoids are compounds derived from mevalonic acid, which have anti-inflammatory, antineoplastic and antibacterial activities. One of the most widely used is paclitaxel, which is used in many centers as an antitumor agent for treating different types of cancer, such as ovarian, breast and lung cancers [19]. Finally, saponins show interesting analgesic, anti-inflammatory and anti-tumor effects [15]. Nanotechnology is defined as the design of structures that have a size set on the nanometric scale (1-100 nm), and these structures are applicable in various sectors such as nutrition [20,21]. In addition, related to health, nanomedicine can be a good tool for cancer diagnosis, tumor cell treatment (development or controlled release of drugs) or tissue regeneration [22]. Additionally, these nanoformulations have been used for the encapsulation of small bioactive plant compounds, such as curcumin or quercetin, with proven efficacy [20]. Therefore, nanotechnology is shown as a strategy to effectively encapsulate bioactive compounds derived from plant extracts, allowing their entry into cells and producing an improved cytotoxic effect compared to the use of free extracts. In addition, natural extracts are a great alternative to traditional drugs because, through their reducing power, they can offer stability to nanoformulations synthesized from them, generating additional cytotoxicity to tumor cells without any damage to non-tumor cells [23]. Previously, metallic nanoformulations (silver and gold) have been presented that are able to encapsulate these compounds correctly based on green synthesis with few steps. This process is based on the reductive capacity of plant extracts, which allows the conversion of metal salts into nanoformulations without requiring other compounds during the synthesis process. In addition, many of these nanoparticles are able to exert a better therapeutic effect compared to the extract from which they are derived since they specifically encapsulate bioactive compounds with the highest cytotoxic activity [24,25]. On the other hand, nanoformulations of other metals (such as nickel) have been synthesized using root extracts and possess clear antioxidant, antibacterial and antitumor activities [26]. The discovery of new plant extracts that possess high cytotoxic activity on tumor cells is of great interest for the possible improvement of current treatments available for CRC. In addition to this, their nanoencapsulation could lead to more effective entry of bioactive compounds into cells, thereby increasing their efficacy.