Antioxidants


Epidemiological studies have indicted that fruits and vegetable decrease the risk of chronic disease such as cancer, and cardiovascular and cerebrovascular disease. The protection from such disease is thought to be due to antioxidants (Simopoulos, 2004).Oxidative damage as result of normal metabolism or environmental pollution leads to the formation of free radicals. Free radicals are electrically charged molecules which seek to capture electrons from other molecules to neutralise themselves, and free radical formation has been considered to play a central role in cancer and the progression of atherosclerosis (Kaliora et al., 2005). Antioxidants are molecules which neutralise free radicals, consuming a diet rich in antioxidants has been associated with the prevention of some diseases (Kaliora et al., 2005). Dietary antioxidants include vitamin E (α-tocopherol), vitamin C (ascorbic acid), carotenoids (β-carotene), flavanoids and lycopene.

Purslane leaves contain α-tocopherol (Vitamin E) levels of 230 ± 9 mg/100g dry weight which is up to ten times higher than other similar plants. Ascorbic acid (Vitamin C) levels are significantly higher than the levels found in spinach (Simopoulos, 2004). The ascorbic acid and α-tocopherol levels amongst other similar plants are shown below. Beta-carotene is an antioxidant of interest in the health arena due to the reasons described earlier, and purslane has been described as an excellent source of beta-carotene (Liu et al., 2000). The beta-carotene content of purslane leaves and stems was determined by Liu et al. (2000) as 21-30 and 3.6-6.5 ug/g fresh weight respectively. The beta-carotene content of the leaves was 3.2 - 8.3 fold higher than the stems, the extent of beta-carotene content dependent on the cultivar analysed (Figure 1 ).

Plant
Vitamin C
Vitamin E
Morning glory
2
10
Lambs quarter
58
12
Alfalfa
143
10
Pigweed
504
10
Buckweed
537
28
Mustard
469
50
Sicklepod
861
60
Velvetleaf
92
50
Jimson weed
114
83
Spinach
430
36
Purslane (wild grown)
451
170
Purslane
(chamber grown)
506
230
Index