Are there any natural remedies for gangrene in a diabetic?

See a specialist! This is not a condition that should be taken lightly and should be properly evaluated by a professional. Gangrene can rapidly beome infected and disseminate into sepsis.
No! Gangrene is a major complication of diabetes when poor blood flow to a limb with damaged nerves causes damage to the tissue. This is a medical emergency where the goal is preserving as much healthy tissue as possible while keeping away infections. While not clear what "natural" means in this setting, this generally requires traditional medical care from a vascular surgeon or wound care team.