**Author details**

oxygen with higher efficiency as compared to the α-tocopherol. More so, β-carotene can be cleaved by β-carotene-15,150-dioxygenase into the two molecules of vitamin A, another

**Table 3.** Some plants/phytochemicals with therapeutic effects on oxidative stress-related diseases and possible

*Aegle marmelos* Ethyl acetate extract Antioxidant activity

**Plant Phytochemical Mechanism of action References**

Curcumin Reduced levels of

as well as potential acetylcholinesterase inhibitory property

oxidative stress and attenuated increased acetylcholinesterase in mice [107]

[108]

**Hydroxycinnamates:** Hydroxycinnamic acids which include ferulic acid, caffeic acid, p-coumaric acid, sinapic acid are another category of dietary antioxidants that are known to protect LDL from oxidation and can prevent coronary heart disease and atherosclerosis [69]. In vitro studies involving human LDL as the oxidizing substrate have shown hydroxy-

Several plants are known to possess antioxidant properties due to the presence of certain phytochemicals that have been shown to exhibit antioxidant activities in *in vitro* and *in vivo* studies as well as in humans. Consumption of vegetables and fruits rich in antioxidant phytochemicals has proven to increase the antioxidant capacity of serum/plasma. For example, consumption of strawberries, red wine, vitamin C or spinach in elderly women significantly increased the total antioxidant capacity of serum as well as plasma vitamin C levels [71]. Also, another study showed the plasma antioxidant capacity to significantly increase after consuming 10 servings of fruits and vegetables per day for 15 days [72]. Apart from vitamins present in these fruits and vegetables, other plant phytochemicals could be accountable for the increased total antioxidant capacity in serum as other studies have shown the presence of anthocyanins in human serum [73]. More so, apples are highly rich in phenolics and flavonoids thus polyphenols may also be accountable for total antioxidant activity in serum. As such, phytochemicals in fruits and vegetables could interact together such that their additive and synergistic effects could potentiate their antioxidant activities [74]. The pathogenesis of some chronic diseases such as cardiovascular diseases, type 2 diabetes, cancer etc. is accompanied by chronic inflammation which is mediated by the release of free radicals by inflammatory cells [75, 76]. Several antioxidant phytochemicals including resveratrol, anthocyanins, and curcumin, have been found to have anti-inflammatory action via inhibition of prostaglandin production, enzyme inhibition and nuclear factor-kB activity, as well as increase of cytokine production [77]. This section highlights on some plants which have shown to possess antioxidant activities *in vitro* and *in vivo* as well as antioxidant phytochemicals against certain

cinnamic acids to have higher antioxidant activity than hydroxybenzoic acids [70].

oxidative stress diseases with their mode of action as summarized in **Tables 2** and **3**.

antioxidant.

mechanism of action.

**Oxidative stress diseases**

64 Phytochemicals - Source of Antioxidants and Role in Disease Prevention

**6.2. Plants with antioxidant properties**

Godwill Azeh Engwa

Address all correspondence to: engwagodwill@gmail.com

Biochemistry, Department of Chemical Sciences, Godfrey Okoye University, Enugu Nigeria
