Table 4.

Influence of processing methods on the functional components of indigenous leafy vegetables.

Indigenous Leafy Vegetable	Processing Method	Effect on the Functional Components and Nutritional Value	Reference
Nightshade	Solar drying	Increased the leaves’ overall carotenoid content by 40%	[14]
		Increased phenolic acids such as caffeoylmalic acid, rutin and kaempferol-3-O-rutinoside in the leaves	[14]
		Increased the chlorogenic and neochlorogenic acid levels in leaves	[14]
		Improved FRAP activity	[14]
	Fermentation	Improved amounts of vitamins B1, B2 and C of the leaves	[184]
		Increased TPC and phenolic compound bioavailability, especially for phenolic acids and flavonoids in the leaves	[185]
	Steaming or cooking in plain hot water	Enhanced the levels of hydroxycinnamic acid derivatives and caffeoylmalic acid	[14]
	Steam blanching (water or lemon juice)	Increased the level of caffeoylmalic acid	[14]
	Stir frying	Increased the amounts of 3-caffeoylquinic, 4-caffeoylquinic and 5-caffeoylquinic acids, Ekaempferol-3-O-rutinoside, chlorogenic acid, caffeoylmalic acid and quercetin-3-O-xylosyl-rutinoside	[14]
Nightshade pickle and relish	Fermentation	Improved the β-carotene content of both products	[186]
Jew’s mallow	Cooking	Improved mineral content (phosphorous, potassium, calcium, magnesium, sodium and micro minerals (iron, manganese, zinc)) of the leaves	[187]
		Enhanced protein, ash and dietary (soluble and insoluble) fibre	[187]
		Improved cellulose and hemicellulose of the leaves and enhanced essential amino acids except phenylalanine	[187]
Chinese cabbage	Blanching in 5% lemon juice	Increased total chlorophyll retention	[128]
		Increased TPC, FRAP and TEAC	[128]
		Improved quinic and ferulic acids	[128]
		Improved levels of kaempferol-dihexoside, sinapoyl malate, rutin, isorhamnetin-O-dihexoside and kaempferol-3-O-hydroxyferuloyl-trihexoside in the leaves	[128]
	Stir frying	Improved levels of kaempferol-3-O-hydroxyferuloyl-trihexoside, kaempferol-dihexoside, sinapoyl malate, rutin and isorhamnetin-O-dihexoside	[128]
	Fermentation	Increased β-carotene content	[188]
		Improved mineral content (iron, zinc, calcium, potassium, copper and nickel)	[188]
Pumpkin leaves	Boiling	Improved the bioaccessibility of most polyphenols apart from methylquinic acid, cis-4-feruloylquinic acid and phenethyl rutinoside	[189]
	Stir frying	Enhanced the release and bioaccessibility of β-carotene as well as antioxidant activities	[189]
		Significantly improved the FRAP activity
	Steam blanching (plain water)	Retained TPC and minimised the loss of quercetin	[93]
		3-glucoside 7-rhamnoside, kaempferol 7-neohesperidoside, isoorientin 2′′-O-rhamnoside, isorhamnetin-3-O-rutinoside, quercetin 3-galactoside, coumaroyl glucaric acid, isorhamnetin-3-galactoside-6′′-rhamnoside, 2-caffeoylisocitric acid and quercetin 3-galactoside 7-rhamnoside
		Enhanced antioxidant capacity (FRAP and ABTS).
Amaranthus leaves	Fermentation	Improved the mineral content (calcium, magnesium, zinc, iron, selenium and copper)	[190]

TPC = total phenolic content.