*7.6.2 Antioxidants*

Root vegetables which are also used as spices are excellent sources of natural antioxidants; they contain antioxidant enzymes like catalase, glutathione peroxidase

#### *Nigeria Root Vegetables: Production, Utilization, Breeding, Biotechnology and Constraints DOI: http://dx.doi.org/10.5772/intechopen.106861*

and superoxide and non-enzymatic antioxidants such as ascorbic acid, polyphenols, carotenoids and chelating agents. Ginger contains polyphenol compounds like gingerol and its derivatives like zingiberone, bisabolene, camphene, geranial, linalool, borneol and oleoresin. These bioactive compounds are responsible for the sensory attributes and capacity to delay food spoilage or inhibit disease causing reactions or agents that have been reported. Diverse bioactive compounds have been reported in garlic [152]. Flavonoids (flavones and quercetins) and sulfur-containing compounds (allyl-cysteine, diallyl sulfide, and allyl trisulfide are found in garlic, and [153] reported the antioxidant properties of the garlic compounds allyl cysteine, alliin, allicin, and ally disulfide. The S- allyl-L-cysteine sulfoxide is converted into allicin (which produces the unique odor associated with garlic). Consumption of garlic preparations have been shown to reduce blood lipid peroxidation while increasing the vitamin E concentration [154]. The curcumin in turmeric is a natural phenolic compound. Apart from being a coloring pigment, it has the capacity to neutralize free radicals [155].

#### *7.6.3 Antimicrobial properties*

The biological and antimicrobial properties of spices are also linked to the presence of bioactive compounds. Allicin present in garlic exhibits a broad spectrum of effects on a variety of fungal species. Phenolic compounds in ginger have high antimicrobial activities and effectiveness for the control of certain viral, bacterial and fungal diseases. These plants are used in many countries for food preservation. Gingerols and gingerdiol are the main anti-fungal components of ginger. Some antiviral properties have been reported for ginger. Ginger is reported to be effective in management of hepatitis C virus infection where viral clearance is affected [156, 157].
