Henamayee et al. [1] reviewed the anti-cancer properties of rhein, a naturally derived anthraquinone found in the rhubarb (Rheum rhabarbarum) leaves and many Aloe species. Current research supports rhein to be a multitargeted cytotoxicity compound. The chemopreventive activity of rhein was demonstrated in vivo or in vitro with various cancer types, including breast, cervical, colon, glioma, leukemia, liver, lung, nasopharyngeal, ovarian, pancreatic, and oral.

Anti-cancer cytotoxicity can directly or indirectly restore the suppressed immune response within the tumor microenvironment. Ooi et al. [2] reviewed the health-promoting properties and clinical applications of rice bran arabinoxylan compound (RBAC), a hydrolyzed extract of defatted rice bran modified with the shiitake mushroom enzyme. RBAC is also an anti-cancer nutraceutical that can upregulate the cytotoxic activity of natural killer cells, enhance phagocytic cellular functions, and induce the maturation and activation of dendritic cells. Moreover, the immunomodulatory, anti-inflammatory, antioxidant, and anti-angiogenic properties of RBAC are also promising for a wide range of applications beyond cancer.

Thymol is a phenolic compound found in the essential oil of thyme (Thymus spp.). Günes-Bayir et al. [3] studied the cytotoxic, genotoxic, and antioxidative effects of thymol on healthy cells and gastric adenocarcinoma cells. The study demonstrated that thymol at low concentrations provides antioxidative protection to healthy cells in vitro while inducing toxic effects in adenocarcinoma cells. The dose-dependent hormetic impact of thymol of different cell lines makes thymol a potential anti-cancer agent.

[References]

1. Henamayee, S.; Banik, K.; Sailo, B.L.; Shabnam, B.; Harsha, C.; Srilakshmi, S.; Naidu, V.G.M.; Baek, S.H.; Ahn, K.S.; Kunnumakkara, A.B. Therapeutic emergence of rhein as a potential anticancer drug: A review of its molecular targets and anticancer properties. Molecules 2020, 25, 2278, doi:10.3390/molecules25102278.
2. Ooi, S.L.; Pak, S.C.; Micalos, P.S.; Schupfer, E.; Lockley, C.; Park, M.H.; Hwang, S.-J. The health-promoting properties and clinical applications of rice bran arabinoxylan modified with shiitake mushroom enzyme—A narrative review. Molecules 2021, 26, 2539, doi:10.3390/molecules26092539.
3. Günes-Bayir, A.; Kocyigit, A.; Guler, E.M.; Dadak, A. In vitro hormetic effect investigation of thymol on human fibroblast and gastric adenocarcinoma cells. Molecules 2020, 25, 3270, doi:10.3390/molecules25143270.