As this discussion suggests, MP contains the same compound that is the medical mainstay of PD treatment. Therefore, for safety purposes, it has to be regarded like any other medication taken for PD, with an understanding of its efficacy, side effects, and potential interactions.
There are many other “natural” products that claim that they help PD. Many of these products make these claims without evidence, or with meager evidence, that they work. Calling a product “natural”, does not let a manufacturer off the hook from proving that the product works. All remedies derived from plants can and should be held to the same standards of proving their efficacy as any other treatment. This typically means that a clinical trial must be conducted to determine whether the treatment works and is safe to use.