Because of the extensive biological functions of natural substances such as bioflavonoids, and their high safety and low costs, they could have high priority application in the health care system. The antioxidant properties of rutin, a polyphenolic bioflavonoid, have been well documented and demonstrated a wide range of pharmacological applications in cancer research. Since chemotherapeutic drugs have a wide range of side effects and rutin is a safe anticancer agent with minor side effects so recent investigations are performed for study of mechanisms of its anticancer effect.Both in-vivo and in-vitro examinations on anticancer mechanisms of this natural agent have been widely carried out. Regulation of different cellular signaling pathways such as Wnt/β-catenin, p53-independent pathway, PI3K/Akt, JAK/STAT, MAPK, p53, apoptosis as well as NF-ĸB signaling pathways helps to mediate the anticancer impacts of this agent. This study tried to review the molecular mechanisms of rutin anticancer effect on various types of cancer. Deep exploration of these anticancer mechanisms can facilitate the development of this beneficial compound for its application in the treatment of different cancers.

The reports show that rutin has good potentials as an anticancer agent; however, rutin has poor bioavailability due to its low aqueous solubility. The present study was aimed at preparing and evaluating physicochemical properties as well as the anticancer activities of rutin nanocrystals (RNs). RNs were prepared via the ultrasonication method. The prepared nanocrystals then were physicochemically characterized by the conventional techniques. The cytotoxic effect of RNs and free rutin on the HN5 head and neck squamous carcinoma cell line was assessed. The HGF1-PI1 cells as normal oral cells were treated by RNs. Cells were also exposed to rutin and RNs to determine their effects on the expression of caspase-8, caspase-9, Bcl-2, and Bax genes. The prepared RNs have a mean particle size of 75 ± 0.16  nm and quasispherical morphology. Rutin displayed no significant cytotoxic effect on HN5 cells to 2000 μM. However, RNs displayed a cytotoxic effect with IC50 of 30.51 μM and 27.34 μM in 24 and 48 h incubation times, respectively ( p < 0.05 ). RNs had cytotoxic effect 100 times more than rutin on HN5 cells. There was no significant cytotoxic effect on HGF1-PI1 treated by RNs in 24 and 48 h. The expression of Bcl-2 mRNA was significantly decreased in attendance of RNs compared to the control group ( p < 0.05 ). The increase in Bax/Bcl-2 ratio was revealed within IC50 of RNs in 24 h. Our results confirm that the anticancer effect of RNs is significantly more than that of rutin. The activation of the mitochondria-dependent apoptotic pathway of RNs occurred via modulation of Bcl-2 and Bax expression. These results suggest that RNs may be useful in the development of a cancer therapy protocol.