4-Methyl-2,4-bis(4-hydroxyphenyl)pent-1-ene

MBP is a phenol derivative with a 3D structure similar to progesterone.^[7] It therefore also shows a similar reactivity and binding to progesterone binding sites in the body. Due to its increased length compared to BPA, MBP binds stronger to progesterone binding sites than the unmetabolized BPA.

BPA is manufactured by acid catalyzed condensation of acetone and phenol, the industrially scaled process is widely known and studied.^{[8][9][10][11][12]} After ingestion of BPA mammals can metabolize it to form MBP as one of the major active metabolites.^[1] A synthetic way to make MBP has also been reported.^[13] In this research, BPA is heated to 240 °C under reduced pressure and in the presence of a catalytic amount of sodium hydroxide. The formed 4-isopropenylphenol then dimerizes to form MBP.

MBP has no currently known uses; however, BPA has been widely used in plastic food packing such as bottles and coatings of metal cans, to protect the food from direct contact with metal. The FDA has assured that accidental consumption of packaging material can occur, but in safe doses. Due to widespread use of BPA, more waste is produced that poses a potential threat to aquatic organisms. In a recently conducted study, statistical data was gathered to assess pollution levels of BPA across the world. Across 31 countries the highest BPA levels were found in fish – 9340 ng/g and it made up 71% of the researched species (117 out of 162). There are also 55 countries which have reported BPA levels with the highest geometric levels of BPA (ng/L) being observed in Iran, Taiwan, Nigeria and Singapore.^[14]

MBP shares similarities with BPA, being one of its active metabolites. Along these, its main mechanism of action is thus also comparable. MBP is an endocrine disruptor. To be more precise, it is an antagonist for estrogen receptor ER-β.^[15] It binds to this receptor instead of estrogen. This receptor is important for the regulation oncogene expression. Uncontrolled activation may lead to an increased risk of ER-regulated cancers such as breast-,^[4] ovarian-,^[5] uterine-, and prostate cancer.^[6]

Computational studies have shown that MBP can function antagonistically to progesterone within the human progesterone receptor. With the potency of binding to the receptor being calculated as numerically close to that of progesterone itself.^[7] The uncontrolled signalling via hPR during crucial times could lead to adverse effects. The main concern being the possibility of this happening during pregnancy. It would have a similar effect as antiprogresteron,^[16] possibly inducing labour and resulting in a miscarriage. BPA, MBP's precursor, has been shown to have toxic effect on oocyte maturation,^[17] and it is thought that MBP could have a similar such pathway.^[18]

MBP is also predicted to target multiple kinases. The most notable among these being CAMK2G, CAMK2D, ERK/Akt, and RIPK1. CAMK2G and CAMK2D belong to the same calcium/calmodulin dependent protein kinase subfamily. These kinases play important roles in signalling pathways in the cardiovascular system. CAMK2G and CAMK2D have been shown to be critical within cardiac remodeling.^[19] While the role and function of these kinases is known, the exact mode of action and effect of MBP upon them remains unexplored.

ERK and Akt are two kinases regulating the cellular signalling surrounding apoptosis of neuronal cells.^[3] MBP interferes with the regular signalling of these two kinases, causing cell death through the activation of ERK and inactivation of Akt. This mechanism of cell death could be a sign of MBP being a risk factor for the development of neurodegenerative diseases. Aside from possibly interfering with ERK/Akt directly, it has also been shown that MBP can target RIPK1. Which plays a role in cell death and inflammation.^[20] Including the activation of ERK and other mitogen-activated protein kinases.^[21]

eNOS or endothelial nitric oxide synthase catalyses the nitric oxide formation within the cell lining of blood vessels. This nitric oxide factors in the process of cell proliferation as well as blood vessel formation and -alteration.^[22] The pathways controlled by eNOS also play key roles in the maintenance of vascular homeostasis.^[23] It has been shown that MBP inhibits the formation of the nitric oxides necessary for these signalling pathways.^[18] Thus possibly leading to detrimental effects to the growth of new blood vessels, and the continued homeostasis of existing ones.

In a study where they research the affinity of MBP and BPA to estrogen receptors (ERα and ERβ) the potency varied among the different assay methods but the estrogenicity of MBP was several-fold to several thousand-fold higher than BPA.^[1]

MBP just like BPA may be linked to the development of diabetes mellitus. BPA is also linked to disorders of reproductive function, obesity, and cancer which in turn might be linked to MBP.^[15]