**6. Some scientifically validated antidiabetic plants**

**Agent Mechanism Site of action Advantages Side effects**

GI tract Low risk

Effective and inexpensive

Weight loss Does not cause hypoglycaemia

Decreases postprandial plasma triglyceride

levels

Hypoglycaemia and weight gain.

Nausea and diarrhoea. Hypoglycaemia occurs when combined with sulfonylurea or insulin

Increased liver enzymes,

gain, oedema, mild

Diarrhoea, abdominal pain, flatulence; Serum levels of

transaminases increases at

weight

anaemia

doses

Pancreatic beta cells

Liver

Fat, muscle

**5. Drug-induced diabetic mellitus and their mechanisms of action**

The most common drugs that are currently being used for the experimental induction of diabetes are alloxan and streptozotocin (STZ). Streptozotocin (STZ) is a synthetic antineoplas‐ tic agent that is classified as an anti-tumour antibiotic and is chemically related to other nitrosureas used in cancer chemotherapy [37]. Intra-venous injection of 60mg/kg dose of streptozotocin in adult Wistar rats, makes pancreas swell and at last causes degeneration in Langerhans islet beta cells and induces experimental diabetes mellitus in 2-4 days [37]. Both alloxan and STZ have been extensively documented for the induction of diabetes via free radical generation and depletion of antioxidant defense system [38-40]. STZ has been reported to significantly decrease the activity of erythrocytes antioxidative enzymes catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GPx) [38-39]. Several drugs, with pharmacological properties including theophylline, aspirin, isoniazid and nalidixic acid can cause transient hyperglycaemia in over dosage, but only streptozotocin, alloxan and the rodenticide vacor are likely to cause permanent diabetes. Alloxan and the product of its reduction, dialuric acid, establish a redox cycle with the formation of superoxide radicals that undergo dismutation to produce hydrogen peroxide via Fenton reaction [41]. Similarly, the

Stimulating insulin production by inhibiting the K-

Decreases insulin resistance

Reduce insulin resistance by activating PPAR-γ

Reduces intestinal

glucose absorption

ATP channel

100 Antioxidant-Antidiabetic Agents and Human Health

Sulphonylureas

Metformin

Thiazolidinediones

α-glucosidase inhibitors

Adapted from Kavishankar *et al*. [36].

**Table 1.** Synthetic drugs and their side effects

Recently, Etuk *et al.* [42] reported that the following medicinal plants have been validated scientifically as potent antidiabetic plants: *Acacia arabica* (Lam.) Muhl. ex Willd. (Family:

Mimosaceae), *Aegle marmelos* (L.) Correa ex Roxb. (Family: Rutaceae), *Allium cepa* L. (Family: Liliaceae), *Allium sativum* L. (Family: Alliaceae), *Aloe vera* (L.) Burm.f. (Family: Aloaceae), *Anthemis mobilis* Linn*.* (Family: Compositae), *Areca catechu* L. (Family: Arecaceae), *Artemisia pallens* Wall. ex DC. (Family: Compositae), *Annona squamosa* L. (Family: Annonaceae), *Andrographis paniculata* Nees (Family: Acanthaceae), *Aerva lanata* (L.) Juss. ex Schult. (Family: Amaranthaceae), *Asteracantha longifolia* Nees (Family: Acanthaceae), *Azadirachta indica* A. Juss. (Family: Meliaceae), *Biophytum sensitivum* (L.) DC. (Family: Oxalidaceae), *Bombax ceiba* L. (Family: Bombacaceae), *Beta vulgaris*

L. (Family: Chenopodiaceae), *Brassica juncea* (L.) Czern. (Family: Brassicaceae), *Barleria lupulina* Lindl. (Family: Acanthaceae), *Boerhavia diffusa* L. (Family: Nyctaginaceae), *Brickellia veronicaefolia* A. Gray (Family: Asteraceae), *Cassia auriculata* L. (Family: Leguminosae), *Caesalpinia bonducella* (L.) Roxb. (Family: Cesalpinaceae), *Capparis decidua* (Forsk.) Edgew. (Family: Capparidaceae) *Cajanus cajan* (L.) Millsp. (Family: Fabaceae), *Citrullus colocynthis* (L.) Schrad. (Family: Cucurbitaceae), *Coccinia indica* Wight & Arn. (Family: Cucurbitaceae), *Casearia esculenta* Roxb. (Family: Flacourtiaceae), *Catharanthus roseus* (L) G. Don. (Family: Apocyna‐ ceae), *Camellia sinensis* Kuntze (Family: Theaceae), *Coriandrum sativum* L. (Family: Apiaceae).
