(3.P) Are natural attacks treated as melee weapons?

[Hogsy]

As the title. For example, one of my players is sporting a DCA/Dragon Shen homebrew of my own making and he wants to put Wrathful Healing on his mighty fists amulet. I couldn't find anything on the web so I'm asking the playground. Does the fact that natural attacks are not specified as melee weapons mean that anything that applies to melee weapons do not apply to natural attacks? If they aren't, does that mean that the Amulet is some sort of specific ruling that bypasses the one above, or are natural attacks simply restricted to flat enhancement bonuses?