Antioxidants from Nigerian Medicinal Plants: What Are the Evidence?

Abstract

The search for natural antioxidants from plants would continue to be a dominant research interest for many years. This is because of the increasing understanding on the role of oxidative stress in damaging cell structures such as DNA, due to over production of free radicals and reactive oxygen species (ROS) in human systems, which are linked to inflammation, cancer and diabetes. However, phenolic compounds especially from phytochemicals or vegetable foods play important roles in reducing the risk of these diseases and reinforces the importance of natural antioxidants in human health. These antioxidant molecules neutralize or quench the ROS by either hydrogen atom transfer or single electron transfer mechanisms. Thus, the capacity to scavenge ROS and free radicals or inhibits lipid peroxidation is measured quantitatively as the strength of antioxidant activity. Several chemical and biochemical protocols have been used in the evaluation of plant extracts as antioxidants. Overwhelming literature reports have indicated varying degrees of antioxidant efficacies of extracts from Nigerian medicinal plants in comparison to synthetic antioxidants. These efficacies were analyzed to provide insight into the strength of antioxidant activity. This chapter reviewed 250 Nigerian medicinal plants in search of evidence for effective antioxidants.

Comparative Anti-Oxidative and Acetylcholinesterase Inhibition Potentials of Selected Plants in Treating Alzheimer’s and Degenerative Diseases

“…Antioxidant compounds may function as free radical scavengers, initiator of the complexes of prooxidant metals, reducing agents and quenchers of singlet oxygen formation. The in vitro antioxidants scavenging potentials results obtained in this study however corroborated the observations of earlier investigations by other researchers worldwide revealing plants as major sources of antioxidants [35][36][37][38][39] . Antioxidant's enzymes (CAT, SOD, GPx, GR and GST) and GSH were also investigated as presented in Fig.…”

Carob Pulp: A Nutritional and Functional By-Product Worldwide Spread in the Formulation of Different Food Products and Beverages. A Review

“…Overall, antioxidants can be classified as enzymatic (primary and secondary enzymes) and non-enzymatic systems. This last group will be discussed throughout the review, and include flavonoids (anthocyanins, flavanones, flavonols, flavones, isoflavonoids, and flavanones), phenolic acids (hydroxycinnamic acids and hydroxybenzoic acids), vitamins (A, C and E), and minerals (Cu, Zn, Se, Mn), among others [125]. They are exogenous providers of protection that are derived through the diet, and can be subclassified as nutrients and non-nutrients [126].…”

“…The non-nutrients, which are good antioxidant agents, include the secondary metabolites in plants, such as the (poly)phenolic compounds and coumarins, which can provide many health-promoting benefits, including antioxidant, antimicrobial, anticancer, anti-inflammatory and antiallergic actions [127]. Because of the complexity of the antioxidant defense system, the optimal benefit of antioxidant supplementation will only be obtained from a mixture of these substances (nutrient and non-nutrient antioxidants), while high levels of a single antioxidant may even be disadvantageous [125,128]. For this reason, a high dietary intake of a diversity of fruits and vegetables is recommended [128].…”