i dont think so because what absorves the microwaves and turns them to heat are the water molecules. water boils at 100 C (212F), therefore in theory is impossible reach higher temperatures than it. even if it were possible, the THC boils at somewhat like 200 C, so there is no need to worry about it.
if you want be sure, microwave just a very small amount of weed... i assure you the weed will just become hot and dry, but no harm will be done to it.
Coelho Reviewed by Coelho on . How to increase the potency of MJ Here there is something i think is the dream of every stoner... how to increase the potency of hemp... and the recipe is very simple: "The potency of marijuana can be increased by about 50% simply by simmering a water slurry of the material for 2 hours. Add water as necessary to maintain the level. Cool and filter the mixture, and refrigerate the aqueous solution. Dry the leaf material at low heat. Drink the tea before smoking the marijuana. The effects are much more intense and last longer Rating: 5