Methods for the treatment of conditions related to hydrogen sulfide

A method comprising, treating a neurodegenerative disease that is associated with decreased activity of H2S in an animal in need thereof, wherein the disease that is associated with decreased activity of H2S in an animal is Alzheimer's disease or Parkinson's disease, by orally administering to the animal, an effective amount of a compound of formula (I) and pharmaceutically acceptable salts thereof

• wherein:
• R1 represents a (1-6C)alkoxycarbonyl group or a (1-6C)alkanoyl group, wherein the (1-6C)alkoxycarbonyl group and the (1-6C)alkanoyl group may bear one, two or three substituents selected from hydroxy, (1-6C)alkoxy, (1-6C)alkanoyloxy, carboxy and (1-6C)alkoxycarbonyl;
• R2 represents a hydroxyl group or a (1-6C)alkoxy group;
• and
• R3 represents a (1-6C)alkanoyl group that may bear one, two or three substituents selected from hydroxy, (1-6C)alkoxy, (1-6C)alkanoyloxy, carboxy and (1-6C)alkoxycarbonyl;
• or
• a compound of formula (IV) and pharmaceutically acceptable salts thereof
• wherein:
• R10 represents a hydrogen atom, a (1-6C)alkoxycarbonyl group or a (1-6C)alkanoyl group, wherein the (1-6C)alkoxycarbonyl group and the (1-6C)alkanoyl group may bear one, two or three substituents selected from hydroxy, (1-6C)alkoxy, (1-6C)alkanoyloxy, carboxy and (1-6C)alkoxycarbonyl;
• and
• one of R11 and R12 represents a (1-6C)alkoxy group, and the other of R11 and R12 represents a hydroxy group or a (1-6C)alkoxy group.