# Plant-Derived Bioactive Compounds for Rhabdomyosarcoma Therapy In Vitro: A Systematic Review
## 4 Discussion  
The incidence of sarcomas is around 7% in children, and half of these patients are diagnosed with RMS [1; 2]. In recent years, despite progress in the treatment of RMS, the results have not been as expected since it has metastasized in more cases. Because of this, new and more effective treatments are needed. Therapies derived from natural products are powerful current and future research tools to use in combination with classic cancer treatments to increase survival and decrease their toxicity [4; 58; 59]. Most of the research studies included in this systematic review are based on in vitro cell death through apoptosis. The most commonly used cell line has been RD, an embryonal RMS cell. However, they have also been used in the most malignant histological variant, that is, the alveolar, being the RH-30 cell line the most used [21; 23; 24; 26; 49]. In RH-30 and RMS-13, both alveolar RMS cell lines, it has been shown that apoptosis can occur both through the intrinsic pathway and through caspase activation [24; 26]. Many of the extracts were obtained with polar solvents, for example, methanol or ethanol. In the specific case of apoptosis, it was observed that methanol is the most commonly used solvent, and its extracts have apoptotic potential against the RH-30 and RD cell lines [21; 23]. On the contrary, it should be noted that, in the scientific literature on extraction methods for bioactive compounds of plant origin, ethanol is the most commonly used for the extraction of polyphenols [60]. However, for RMS cells, most of the extracts were obtained with methanol, showing high amounts of polyphenols and flavonoids. Flavonoids and phenols are the most common bioactive compounds in plant extracts. The extraction methodology using solvents such as methanol and ethanol enhances the extraction of these bioactive compounds [61]. Although these extracts may contain other compounds, it is those of a phenolic nature that present the greatest antioxidant and antitumor bioactivity. In fact, in the case of _Phyllanthus deblilis_ extract [62], the antiproliferative and antioxidant activity were greater in plant roots since they contained more phenols. The IC\({}_{50}\) value of the root extract in the RD cell line was 216.52 \(\pm\) 11.90 \(\upmu\)g/mL, highlighting that _Phyllanthus deblilis_ did not show cytotoxicity against healthy cells used as a control (CC-1). Regarding the analysis of plants studied in this systematic review, _Cherospondias axillaris_[49; 50] was the only plant species studied in two different scientific articles published in 2020. Its mechanism of action was different depending on the part of the plant used for the extract, showing better results from the extract obtained from its fruits. Therefore, it is important to know which part of the plant has been used for the extract since they may have different compounds. The genus _Veronica_ appeared in two different studies, although they analyzed different species [28; 43]. Some species of the genus _Berberis_ were analyzed in three different articles, according to which apoptosis was the mechanism of cell death [23; 24; 27]. However, this does not mean that these plant extracts or isolated bioactive compounds were more relevant than the rest against RMS. In addition to the use of the plant extract against the tumor individually, synergy studies have been carried out with the chemotherapy regimens used clinically. In seven of the articles included in this systematic review, the functional extracts were studied together with or in comparison with chemotherapy drugs. Some of them have proven that the combination of chemotherapy and plant extract achieves a greater cytotoxic effect against tumor cells and less toxicity in non-tumor cells, as shown in _Curcuma amada_, _Ficus carica_, _Tecoma stans_, and _Narcissus tazetta_[19; 26; 39]. In four articles, the antitumor activity of the extract was simply compared with that of the chemotherapy agent, as in the methanol extract of _Spondias mombin_ seeds against the RD cell line.