"There are also radioprotectant drugs used on Earth to treat radiation exposure"
Uhm, not really. I am not aware of any valid scientific evidence of anything that protects against radiation.
There are 2 possible things you were thinking of here, the most likely being those radiation pills that were handed out during chernobyl and fukushima. These pills do not directly protect against radiation, but simply help the body remove certain elements such as Iodine and Strontium. These are by far the most dangerous releases from both accidents as the body focuses them in relatively small areas ( in the case of Iodine, it's in the Thyroid Gland, massively increasing the chances of Thyroid Cancer. ) Naturally, these would not work at all on Mars as you are not ingesting radioactive Iodine there. There are indeed some pretty nasty potential side-effects from these, but it's better than cancer.
The second possibility is a pair of herbs that each had a study done and found the blood samples tested were partially protected against the effects of radiation.
Sounds good...until you read that the test contained a whopping 5 samples. If you tossed a coin 5 times, and got tails 5 times..I'd hardly say that's evidence for a coin always landing on tails.
Then theres also a bunch of typical new age claims with absolutely no real evidence. They couldn't even be bothered to do a test of 5 samples.