What does "gamma" in gamma-oryzanol mean?

The structure of gamma-oryzanol is:


[![γ-Oryzanol structure](https://i.stack.imgur.com/YOelF.png)](https://i.stack.imgur.com/YOelF.png)


What does the "gamma" in its name mean?




No designations such as alpha-oryzanol, beta-oryzanol, etc. appear to be in use, and according to [this WebMD entry](http://www.webmd.com/vitamins-supplements/ingredientmono-770-gamma%20oryzanol.aspx?activeingredientid=770), as well as [this PubChem document](https://pubchem.ncbi.nlm.nih.gov/compound/6450219#section=Top), another name for gamma-oryzanol is simply "oryzanol". 


There seems to be some ambiguity as to just what oryzanol, or gamma-oryzanol refers to. According to [Chemical Book](http://www.chemicalbook.com/ProductChemicalPropertiesCB5758140_EN.htm): 



> 
> Gamma Oryzanol is a mixture of 6 substances derived from rice bran oil, including sterols and ferulic acid, called Cycloartanyl Ferulate or Triterpene alcohol ferulate. 
> 
> 
> 


But then other sources, including [this US National Institutes of Health](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4377434/) publication, consider gamma-oryzanol composed of four components: 



> 
> There are four main components of γ-oryzanols, namely, cycloartenyl ferulate, 24-methylene cycloartenyl ferulate, campesteryl ferulate, and sitosteryl ferulate [original publication: *Lerma-García M. J., Herrero-Martínez J. M., Simó-Alfonso E. F., Mendonça C. R. B., Ramis-Ramos G. Composition, industrial processing and applications of rice bran γ-oryzanol. Food Chemistry. 2009;115(2):389–404. doi: 10.1016/j.foodchem.2009.01.063* 
> 
> 
> 


Further confusing the issue is that the PubChem article referenced above gives a single structure for gamma oryzanol (the same as that given in the OP), but does not include any physical properties that one would expect for a single pure compound (i.e. no melting point, solubility, vapor pressure data) although it does give the molecular weight. Again, PubChem lists "oryzanol" as a synonym and does not have any other oryzanol-named compound in it's database.


**Summary TL/DR:**  

The gamma in "gamma-oryzanol" doesn't refer to a specific structure or isomer and there is no corresponding compounds named alpha-oryzanol, beta-oryzanol, etc. Rather, the term gamma-oryzanol is also simply called "oryzanol" and it refers to a combination of several different moieties as described above.


 8

Some works directly mention the alpha and beta designated substances – that were (incl. gamma) rather fractions obtained during first historic isolations:[1]



> 
> (…) Oryzanol occurs in the unsaponifiable fraction of rice bran oil and is so named because it was first discovered in rice bran oil (*Orysae Sativa L.*) (Kaneko and Tsuchiya, 1954)[2] and contained a hydroxyl group. Oryzanol was originally considered a single compound but later was determined to be a mixture of ferulic acids esterified with normal sterols or triterpene alcohols, called **α-**, **β-** and **γ-oryzanol**, of which γ-oryzanol has been the most commonly mentioned. The sterol components of γ-oryzanol are primarily campesterol and sitosterol, and the triterpene alcohol components are cycloartenol and 24-methylene cycloartanol (…)
> 
> 
> 


Other text sound like alpha a beta fractions were not oryzanol at all:[3]



> 
> (…) During their studies, a number of lipid fractions were isolated from rice bran oil; the third (**gamma**) fraction isolated was **oryzanol**[2]. Its chemical composition was later identified as a mixture of 
>  ferulic acid esters of various plant sterols (…)
> 
> 
> 


(Hard to tell, the article[2] is in Japanese.)


As airhuff already said in his answer, **γ-oryzanol** (or just **oryzanol**) is a mixture of various sterol [ferulates](https://en.wikipedia.org/wiki/Ferulic_acid), which now usually are listed by their chemical names, however a couple of notable compendia[4,5] list the two major[6] formerly isolated constituents under names **oryzanol A** and **C** (no B, since it turned out to be a mixture of A and C[7]).


![Fig. - structures](https://i.stack.imgur.com/OHIKt.png)


* (I) **oryzanol A**, CAS 21238-33-5, cycloartenyl ferulate,  

9,19-cyclo-5α-lanost-24-en-3β-yl (2*E*)-3-(4-hydroxy-3-methoxyphenyl)prop-2-enoate
* (II) **oryzanol C**, CAS 469-36-3, 24-methylenecycloartanyl ferulate,  

24-methylidene-9,19-cyclo-5α-lanostan-3β-yl (2*E*)-3-(4-hydroxy-3-methoxyphenyl)prop-2-enoate


Your structure happens to be **oryzanol A**.




---


References:


1. Huang, C. J. [Potential Functionality and Digestibility of Oryzanol as Determined Using in Vitro Cell Culture Models](https://digitalcommons.lsu.edu/gradschool_dissertations/261), Dissertation thesis, Louisiana State University and Agricultural and Mechanical College, **2003**.
2. Kaneko, R.; Tsuchiya, T. [New Compound in Rice Bran and Germ Oils](https://doi.org/10.1246/nikkashi1898.57.526). *J. Chem. Soc. Jpn.* **1954**, *57*, 526–529.
3. Wheeler, K. B.; Garleb, K. A. [Gamma Oryzanol—Plant Sterol Supplementation: Metabolic, Endocrine, and Physiologic Effects](https://doi.org/10.1123/ijsn.1.2.170). *International Journal of Sport Nutrition* **1991**, *1* (2), 170–177.
4. O’Neil, M. J.; Heckelman, P.; Koch, C.; Roman, K. *The Merck Index*, 14th ed.; **2006**.
5. Hill, R. A.; Makin, H.; Kirk, D.; Murphy, G. Dictionary of Steroids; CRC Press, **1991**.
6. Xu, Z.; Godber, J. S. [Purification and Identification of Components of γ-Oryzanol in Rice Bran Oil](https://doi.org/10.1021/jf981175j). *J. Agric. Food Chem*. **1999**, *47* (7), 2724–2728.
7. Shimizu, M.; Ohta, G. [Studies on the Constituents of Rice Bran Oil. V. Reexamination of Oryzanol-B](https://doi.org/10.1248/cpb.8.108). *Chem. Pharm. Bull.* **1960**, *8* (2), 108–111.


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