Cancer:
Lung, colon, acute myeloid leukemia, T lymphoma, Ehrlich carcinoma, gastric, esophageal squamous cell, chronic myelogenous leukemia

Action: Dox-induced cardiotoxicity, anti-oxidant

Isorhamnetin, the anti-tumor component of Hippophae rhamnoides Linn, is also a member of the ßavonoid class of compounds. Its chemical name is 3,5,7-trihydroxy-2-(4-hydroxy-3-methoxyphenyl) chromen-4-one and its molecular formula is C16H12O7.

Lung Cancer

Isorhamnetin shows good inhibitory effects on human lung adenocarcinoma A549 cells, human colon cancer HT-29 cells, human chronic myeloid leukemia K562 cells, human acute myeloid leukemia HL-60 cells, mouse T lymphoma YAC-1 cells and mouse Ehrlich carcinoma. In terms of its mechanism of action, it seems that isorhamnetin simultaneously reduces the expression of Bcl-2 and increases the expression of Bax, which activates caspase-9 and its downstream factor caspase-3, thus resulting in cell death (Zhu et al. 2005).

Colorectal Cancer

It was demonstrated that isorhamnetin prevents colorectal tumorigenesis. Dietary isorhamnetin decreased mortality, tumor number, and tumor burden by 62%, 35%, and 59%, respectively. Magnetic resonance imaging, histopathology, and immunohistochemical analysis revealed that dietary isorhamnetin resolved the DSS-induced inflammatory response faster than control diet.

These observations suggest the chemo-protective effects of isorhamnetin in colon cancer are linked to its anti-inflammatory activities and its inhibition of oncogenic Src activity and consequential loss of nuclear β-catenin, activities that are dependent on CSK expression (Saud et al., 2013).

Gastric Cancer

The potential effects of isorhamnetin (IH), a 3'-O-methylated metabolite of quercetin, were investigated on the peroxisome proliferator-activated receptor γ (PPAR-γ) signaling cascade using proteomics technology platform, gastric cancer (GC) cell lines, and xenograft mice model.

It was observed that IH exerted a strong anti-proliferative effect and increased cytotoxicity in combination with chemotherapeutic drugs. IH also inhibited the migratory/invasive properties of gastric cancer cells, which could be reversed in the presence of PPAR-γ inhibitor.

Using molecular docking analysis, Ramachandran et al. (2013) demonstratd that IH formed interactions with seven polar residues and six nonpolar residues within the ligand-binding pocket of PPAR-γ that are reported to be critical for its activity and could competitively bind to PPAR-γ. IH significantly increased the expression of PPAR-γ in tumor tissues obtained from xenograft model of GC. Overall, these findings clearly indicate that anti-tumor effects of IH may be mediated through modulation of the PPAR-γ activation pathway in GC.

Cardiac-protective; Doxorubicin

Isorhamnetin is a natural anti-oxidant with obvious cardiac-protective effect. Its action against doxorubicin-induced cardotoxicity and underlying mechanisms were investigated. Doxorubicin (Dox) is an anthracycline antibiotic for cancer therapy with limited usage due to cardiotoxicity. The aim of this study is to investigate the possible protective effect of isorhamnetin against Dox-induced cardiotoxicity and its underlying mechanisms. In an in vivo investigation, rats were intraperitoneally (i.p.) administered with Dox to duplicate the model of Dox-induced chronic cardiotoxicity.

Daily pre-treatment with isorhamnetin (5 mg/kg, i.p.) for 7 days was found to reduce Dox-induced myocardial damage significantly, including the decline of cardiac index, decrease in the release of serum cardiac enzymes, and amelioration of heart vacuolation. In vitro studies on H9c2 cardiomyocytes, isorhamnetin was effective to reduce Dox-induced cell toxicity. Isorhamnetin also potentiated the anti-cancer activity of Dox in MCF-7, HepG2 and Hep2 cells. These findings indicated that isorhamnetin can be used as an adjuvant therapy for the long-term clinical use of Dox (Sun et al., 2013).

Chronic Myelogenous Leukemia

The isorhamnetin 3-o-robinobioside and its original extract, ethyl acetate extract, from Nitraria retusa leaves, were evaluated for their ability to induce anti-oxidant and anti-genotoxic effects in human chronic myelogenous leukemia cell line. They were shown to have a great anti-oxidant and anti-genotoxic potential on human chronic myelogenous leukemia cell line K562 (Boubaker et al., 2012).

Esophageal Cancer

The flavonol aglycone isorhamnetin shows anti-proliferative activity in a variety of cancer cells and it inhibits the proliferation of human esophageal squamous carcinoma Eca-109 cells in vitro (Shi et al., 2012).

Cancer:
Actions: Overcomes MDR; P-glycoproteins, breast cancer resistance proteins (BCRP), efflux transporters

Flavonoid isorhamnetin occurs in various plants and herbs, and demonstrates various biological effects in humans. This work will clarify the isorhamnetin absorption mechanism using the Caco-2 monolayer cell model. The isorhamnetin transport characteristics at different concentrations, pHs, temperatures, tight junctions and potential transporters were systemically investigated.

Isorhamnetin was poorly absorbed by both passive diffusion and active transport mechanisms. Both trans- and paracellular pathways were involved during isorhamnetin transport. Active transport under an ATP-dependent transport mechanism was mediated by the organic anion transporting peptide (OATP); isorhamnetin’s permeability from the apical to the basolateral side significantly decreased after estrone-3-sulfate was added (p<0.01).

Efflux transporters, P-glycoproteins (P-gp), breast cancer resistance proteins (BCRP) and multidrug resistance proteins (MRPs) participated in the isorhamnetin transport process. Among them, the MRPs (especially MRP2) were the main efflux transporters for isorhamnetin; transport from the apical to the basolateral side increased 10.8-fold after adding an MRP inhibitor (MK571).

References

Boubaker J, Ben Sghaier M, Skandrani I, et al. (2012). Isorhamnetin 3-O-robinobioside from Nitraria retusa leaves enhance anti-oxidant and anti-genotoxic activity in human chronic myelogenous leukemia cell line K562. BMC Complement Altern Med, 12:135. doi: 10.1186/1472-6882-12-135.

Ramachandran L, Manu KA, Shanmugam MK, et al. (2013). Isorhamnetin inhibits proliferation and invasion and induces apoptosis through the modulation of peroxisome proliferator-activated receptor γ activation pathway in gastric cancer. J Biol Chem, 288(26):18777. doi: 10.1074/jbc.A112.388702.

Saud SM, Young MR, Jones-Hall YL, et al. (2013). Chemo-preventive activity of plant flavonoid isorhamnetin in colorectal cancer is mediated by oncogenic Src and β -catenin. Cancer Res, 73:5473.

Shi C, Fan LY, Cai Z, Liu YY, Yang CL. (2012). Cellular stress response in Eca-109 cells inhibits apoptosis during early exposure to isorhamnetin. Neoplasma, 59(4):361-9. doi: 10.4149/neo_2012_047.

Sun J, Sun G, Meng X, et al. (2013). Isorhamnetin protects against doxorubicin-induced cardiotoxicity in vivo and in vitro. PLoS One, 8(5):e64526. doi: 10.1371/journal.pone.0064526.

Zhu L, Wang ZR, Zhou LM, et al. (2005). Effects and mechanisms of isorhamnetin on lung carcinoma. Space Med Med Eng (Chin), 18:381-383.

Duan J, Xie Y, Luo H, Li G, Wu T, Zhang T. (2014) Transport characteristics of isorhamnetin across intestinal Caco-2 cell monolayers and the effects of transporters on it. Food Chem Toxicol. 2014 Apr;66:313-20. doi: 10.1016/j.fct.2014.02.003.