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P-1571 4α-Phorbol 12,13-Diacetate, >99%

[4α-PDA]

P-1571PR

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M.W. 448.51

C₂₄H₃₂O₈

[56144-62-8]

Storage: Store at or below -20 ºC in the dark. Solubility: Soluble in DMSO or ethanol. Disposal: A

IMPORTANT NEW DATA: 4α-Phorbol Ester Activation of TRPV4 Channels! Though long thought to be a biologically inactive or extremely weak phorbol ester analog (i. e., an ED50 >25 µM for binding to protein kinase C), 4α-PDA may prove to be a modestly potent activator of TRPV4 channels, with utility for structure-activity studies of this phenomenon. The supposition of agonist activity for 4α-PDA on TRPV4 channels is based on the potent agonist response elicited by the very similar compound, 4α-PDD, in systems containing human VRL-2 and murine TRP12 channels [Watanabe, H., et al. "Activation of TRPV4 channels (hVRL-2/mTRP12) by phorbol derivatives." J. Biol. Chem. 277: 13569-13577 (2002)]. See the entry for 4α -PDD, Cat. No. P-2170, for an extensive description of these new and exciting results.

Chemical Structures. The primary structural difference between 4α-PDA and the highly potent phorbol ester-type PKC activators is the configuration at C4. In the highly active phorbol ester family, the hydroxy group at C4 is in the β configuration, i. e., rising up out of the two-dimensional structure as viewed on paper or a computer monitor. The 4α-phorbol esters such as 4α-PDBu, 4α-PDD, 4α-PDA, and 4α-PMA have the 4-OH group oriented down below the paper or computer screen's two-dimensional plane.

Nomenclature. Unless "4α" is specified, all "phorbol" compounds are automatically defined, by operation of standard chemical nomenclature conventions, as having the 4β-configuration, as part of the meaning of the word "phorbol". This is much like the word "cholesterol", which automatically means that its hydroxy group at carbon 3 is in the β configuration; there is no need to specify "3β-cholesterol", whereas a cholesterol derivative with a 3α hydroxy group would require a "3α-cholesterol" specification.

To avoid confusion in this field, it is useful to note that, technically, 4α-PDA is not a "phorbol ester", it is a "4α-phorbol ester", and the structural differences, though minor overall, are quite significant biologically. Given the extreme differences in their biological properties, both on PKC and TRPV4 channel-based phenomena, efforts to maintain distinctive names for members of these two biologically quite distinct classes of compounds appear to be well justified.