GAA and obesity due to melanocortin 4 receptor deficiency: They can be categorized into the following groups: (a) plant serine protease inhibitors for their potential use in agriculture like plant defense, (b) alpha-glucosidase inhibitors from plants as potential candidates for the treatment of type 2 diabetes, and (c) carbonic anhydrase inhibitors as candidates for the treatment of glaucoma and obesity (Figure 1).