There is only one specific species of hoodia that has been claimed to have appetite suppressant qualities: Hoodia gordonii. A product could say it has "hoodia" and contain another species, not this one.
There is no published research that shows that any company has been able to manufacture an effective drug based on hoodia gordonii. A few major pharm companies (such as Pfizer) have held the rights to make such a drug, but never found a way to do it.
Even if some "miracle" over-the-counter supplement claimed to have hoodia of any type, there is no guarantee that it would. Many many many many nutritional supplements are found, upon testing, that they contain little or none of the active ingredient they claim to have.