No designations such as alpha-oryzanol, beta-oryzanol, etc. appear to be in use, and according to [this WebMD entry][1], as well as [this PubChem document][2], 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][3]:  

>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][4] 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.


  [1]: http://www.webmd.com/vitamins-supplements/ingredientmono-770-gamma%20oryzanol.aspx?activeingredientid=770
  [2]: https://pubchem.ncbi.nlm.nih.gov/compound/6450219#section=Top
  [3]: http://www.chemicalbook.com/ProductChemicalPropertiesCB5758140_EN.htm
  [4]: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4377434/