Change in the Ascorbic Acid, Total Phenol and Antioxidant Activity of Sun-dried Commonly Consumed Green Leafy Vegetables in Nigeria

Abstract

Sun-drying of green leafy vegetables is popularly practised in many homes in Nigeria, as a way of preserving green leafy vegetables for future use. This project sought to investigate the effect of this method of preservation of vegetables on the antioxidant phytoconstituent (Vitamin C and Total phenol) and activity (reducing property and free radical scavenging ability) of some commonly consumed green leafy vegetables in Nigeria namely Structium sparejanophora (Ewuro-odo), Amarantus cruentus (Atetedaye), Telfairia occidentalis (Ugu), Baselia allia (Amunu tutu), Solanum macrocarpon (Igbagba), Corchorus olitorius (Ewedu), Vernonia anygdalina (Ewuro) and Occimum graticimum (Efinrin). The edible portions of the green leafy vegetables were sun-dried for seven days before determining the Vitamin C and total phenol content, as well as the reducing property and free radical scavenging ability. The result of the study revealed that sun-drying of green leafy vegetables cause a significant (P < 0.05) decrease in the Vitamin C content (16.67-64.68% loss). Conversely it leads to a significant increase in the total phenol content (6.45-223.08% gain), reducing property (16.00-362.50% gain) and free radical scavenging ability (126.00-5757.00% gain) of the green leafy vegetables. It could therefore be concluded that a significant decrease (P < 0.05) in Vitamin C content caused by sun- drying will not reduce the antioxidant activity of the green leafy vegetable, moreover, the phenol constituent of the green leafy vegetables contributes more to the antioxidant properties of vegetables than ascorbic acid, as its increase on sun-drying cause a significant (P < 0.05) increases in the antioxidant properties of the green leafy vegetables, irrespective of the decrease in the ascorbic acid content.

Inhibition of α-amylase and α-glucosidase activities by ethanolic extract of Telfairia occidentalis (fluted pumpkin) leaf

“…The result revealed that unprocessed T. occidentalis leaf had a significantly (P<0.05) higher total phenol (13.0 mg/100g) and flavonoid (7.3 [10] reported for some tropical green leafy vegetables (1 -3 mg/g). The difference in phenolic value is as a result of the extraction medium used in the study.…”

“…However, numerous studies have conclusively shown that the majority of the antioxidant activity may be from compound such as flavonoids, isoflavone, flavones, anthocyanin, catechin and isocatechin, rather than vitamins C, E and 毬-carotene [8] . Several green leafy vegetables with high phenolic contents abound in tropical Africa, they are utilized either as condiments or spices in human diets [9] ; these vegetables could be harvested at all stages in the process of growth, and could be fed upon in fresh, processed, or semiprocessed forms [10,11] . They are very rich sources of 毬-carotene, ascorbic acid, minerals and dietary fiber [12] .…”

“…Blanching stops the enzyme action, sets the colour, and shortens the drying and dehydration time [10] . Telfairia occidentalis Hook f. (Curcubitaceae) (T. occidentalis) is a fluted pumpkin and is one of the green leafy vegetables widely consumed in Nigeria [14] .…”

“…Telfairia occidentalis Hook f. (Curcubitaceae) (T. occidentalis) is a fluted pumpkin and is one of the green leafy vegetables widely consumed in Nigeria [14] . Leaves from this plant constitute an important ingredient in soup making since they are good sources of proteins, vitamins (B-complex), minerals, fatty acids (linoleic and oleic acids), and fibers [10] . The vitamin C content of this plant is about 148.0 mg/100 g of dry matter [10] .…”

“…Leaves from this plant constitute an important ingredient in soup making since they are good sources of proteins, vitamins (B-complex), minerals, fatty acids (linoleic and oleic acids), and fibers [10] . The vitamin C content of this plant is about 148.0 mg/100 g of dry matter [10] . T. occidentalis has been reported to protect against cancers of the esophagus, oral cavity, and stomach, to maintain blood vessel flexibility, and to improve circulation in the arteries of smokers [15,16] .…”