**6. Selected antioxidant-rich natural plants with antidiabetic potentials**

### **6.1.** *Sclerocarya birrea*

**Figure 7.** The chemical structure of catechins

326 Antioxidant-Antidiabetic Agents and Human Health

**Figure 8.** The chemical structure of cinnamic acid.

Cinnamon, used extensively since ancient times in food as a herb or spice, has been shown to ameliorate the symptomsofmetabolic syndromes, suchas insulinresistance andelevatedlevels of glucose and lipids [166]. Cinnamon bark contains cinnamic acid, cinnamaldehyde and cinnamic alcohol [167]. Cinnamic acid has been reported to exhibit several pharmacological propertiesincludinghepatoprotective[168],antioxidant[169]andanti-diabeticproperties[170].

Cinnamic acid was recently reported to be capable of preventing advanced glucated endproducts (AGEs)-mediated diabetic complications. It inhibited the formation of AGEs in a bovine serum albumin (BSA)/fructose system, as well as reduced the levels of fructosamine, the formation of N-(carboxymethyl) lysine (CML) and the level of amyloid cross beta-structure [167]. Sinapic acid is a 4-hydroxy-3, 5-dimethoxy cinnamic acid derivative. It is widely distributed in edible plants such as cereals, nuts, oil seeds and berries [171]. Sinapic acid is a potent antioxidant [172]. Sinapic acid possesses potential anti-hyperglycemic effects, through an increase in insulin production associated with a subsequent increase in the activity of

**5.7. Cinnamic acids**

*Sclerocarya birrea* (Family : Anacardiaceae) is a medium-size-to-large deciduous tree widely used for the treatment of proctitis, dysentery, and diarrhea in South Africa and Africa at large and its antimicrobial and antiparasitic properties has been documented [174-175]. *Sclerocarya birrea* is widely used as traditional remedy against diabetes in Africa [176] and has a significant hypoglycemic effect [177]. The methanolic extracts of different parts of the tree such as the leaves, fruit juice, roots and stem-bark has antioxidant properties [61] due to high contents of flavonoids and polyphenolic compounds.

**Figure 9.** *Sclerocarya birrea* plant

#### **6.2.** *Prosopis glandulosa*

*Prosopis glandulosa* (Family: Fabaceae) commonly known as Honey mesquite is a small to medium height tree or shrub that is thorny and branching near the ground found mostly in southern parts of India. The bark and leaves are used by the tribes and native medical practitioners to treat various ailments such as leprosy, dysentery, bronchitis, asthma, leuco‐ derma, piles, and tremors of the muscles, tumors, eye diseases and rheumatism [178]. It is commonly found in the dry, arid regions of the northern and north-western Cape of South Africa. Literature studies have indicated that the plant contains flavan-3-ol dimer, mesquitol [179-180] and catechin [181]. Phytochemical screening of leaves from *Prosopis glandulosa* indicates the presence of alkaloids, glycosides, flavonoids, phenolic compounds, steroids and terpenoids [182].

**7. Conclusion**

over the world.

**Author details**

Ayodeji B. Oyenihi1

ban, South Africa

The pathophysiology of most of the diseases affecting mankind today (*diabetes mellitus* inclusive) seems to have a common denominator, namely oxidative stress. Although, it is a wide topic with several theories, mechanisms, sites and targets of action, reactive oxygen species (ROS) have been implicated in the management of many diseases. As a result, antiox‐ idants have received overwhelming attention in recent years with many outstanding achieve‐ ments. Most therapeutic agents and drugs are either antioxidants or act primarily to prevent the formation of excess ROS. Therefore it is not surprising to note that natural products with antioxidant properties from plant origin are again gaining prominence in research circles all

Antioxidant -Rich Natural Products and Diabetes Mellitus

http://dx.doi.org/10.5772/57192

329

Currently, a lot of therapeutic agents with different modes of action have been designed to combat hyperglycemia; the efficacy and effectiveness of these agents are limited due to several reasons. Individual agent with particular mechanism of action can only act on part of the pathogenic process and only to a partial extent [188-189]. Also, several defects in the patho‐ physiology of diabetes remain unresolved, and therefore, result in the inability to single out a drug target to focus on as human systems are too interwoven and complex to be fully under‐ stood through conventional experimental protocols [190]. However, combination of natural products and phytomedicines from different plants present in most traditional medicines appears to take a different, more holistic approach. These medicinal preparations contain a variety of natural products that act synergistically on a variety of targets through different mechanisms fighting the disease in a more efficient manner. Consequently, the conventional, unidirectional therapeutic method in the management of diabetes seems to be gradually

, Oluwafemi O. Oguntibeju3

1 Department of Biochemistry, School of Life Sciences, University of KwaZulu-Natal, Dur‐

2 Department of Wellness Sciences, Faculty of Health & Wellness Sciences, Cape Peninsula

3 Oxidative Stress Research Centre, Departments of Biomedical Sciences, Faculty of Health and Wellness Sciences, Cape Peninsula University of Technology, Bellville, South Africa

4 Department of Biomedical Sciences, Faculty of Health and Wellness Sciences, Cape Penin‐

and Guillaume Aboua4

replaced by a more holistic, multidimensional approach

, Nicole L. Brooks2

University of Technology, Bellville, South Africa

sula University of Technology, Bellville, South Africa

**Figure 10.** *Prosopis glandulosa* plant

#### **6.3.** *Tamarindus indica*

*Tamarindus indica* Linn (Family: caesalpiniaceae) is a plant that grows naturally in tropical and subtropical regions and has become an important plant for food, herbs in many parts of the world [183]. Literature studies reported *Tamarindus indica* as a traditional medicine for the management of diabetes mellitus in human and experimental animals [184-185]. Siddhuraju [183] reported the potential antioxidant activity of *Tamarindus indica* seeds isolating the antioxidant components 2-hydroxy-30,40-dihydroxyacetophenone, methyl 3,4- ihydroxyben‐ zoate, 3,4-dihydroxyphenylacetate and oligomeric proanthocyanidins. Phenolic compounds such as procyanidin B2, epicatechin, procyanidin trimer, procyanidin tetramer, procyanidin pentamer, procyanidin hexamer, polymeric tannins, polymeric tannins are also present in the seeds of *Tamarindus indica* [186]. It has been postulated that the antidiabetic property of *Tamarindus indica* observed in experimental animals may be due to the presence of the antioxidant-rich compounds [187].

**Figure 11.** Tamarindus indica plant
