You cannot patent something which exists in nature. This is the main reason that pharmaceutical companies ignore plant based drugs and go for deadly chemical cocktails ... further lines of BS
Pharmaceutical companies get patent protection for the *processes* that make ALL KINDS of things that already exist in nature - and don't discriminate between molecules that originated in plants, animals, bacteria, fungi, or anything else.
Biotech firms take it a step further (or closer, as the case may be), in that we tend to target those large, very complex molecules (like proteins) that are much more specifically targeted to the disease/symptom of interest, so as not to cause all the collateral damage side effects. DNA patents don't even enter into it. We usually patent the process for making the end product, and may also try to patent the product itself IF we have made some small modification to it.
The process goes something like this:
(1) Find the gene that codes for a particular protein of interest in the human body.
(2) Change that gene just a little bit so that the final protein is also changed a little bit, ostensibly to improve the 'performance' of the protein (e.g., make it last longer in the body)
(2) Splice that gene into a cell line that you can get to grow fast and make many, many copies of that protein.
(3) Patent the process of making that protein outside of the human body (it's novel)
(4) Also patent the protein itself - it's been changed enough that it does NOT exist in nature.
(5) Profit! *
* Step 5 only occurs after 10-15 years of development, testing, scale-up, clinical trials, and several hundred millions of dollars - sometimes billions - and only about 1% of proteins hat start out looking good make it to the end of the process. And timing your patent application is crucial - apply too late, and another company could scoop you, but apply too soon, and by the time the product is approved by the FDA and ready to market, you could have used up a good portion of the years of your patent protection.