G. Minerals
III. Ascorbic Acid
Capsicum fruit have long been recognized as an excellent source of ascorbic acid, which is a required nutrient for humans. Svent-Gyorgyi isolated ascorbic acid from paprika fruit in the early 1930s, and subsequently identified the compound in 1933.15 Ascorbic acid has strong reducing properties due to its enediol structure, which is conjugated with the carbonyl group in a lactone ring16 (Figure 9.1). In the presence of oxygen, ascorbic acid is degraded to dehydroascorbic acid (DHA), which still retains vitamin C activity. However, upon further oxidation, the lactone ring of DHA is destroyed, resulting in formation of 2,3-diketogulonic acid and loss of vitamin activity.
Ascorbic acid is required for collagen formation and prevention of scurvy. Researchers have postulated a role of ascorbic acid in the prevention of degenerative conditions, including cancer, heart disease, cataracts, and stimulation of the immune system.17 Prevention of chronic diseases may be attributed to the ascorbate function as an aqueous reducing agent. Ascorbate can reduce superoxide, hydroxyl, and other ROS, which may be present in both intracellular and extracellular matrices. Ascorbate within cells participates as an electron donor, as part of the interaction between iron and ferritin. Extracellularly, ascorbate may act in concert with tocopherols in lipid membranes, to quench ROS and prevent lipid peroxidation. Thus, ascorbate may help prevent the oxidation of low-density lipoprotein (LDL), which is thought to be a major initiating step in the process of atherosclerosis. The role of ascorbate in cancer prevention may be attributed to its ability to block
Antioxidant Vitamin and Phytochemical Content of Fresh and Processed Pepper Fruit 167
the formation of N-nitrosamines and nitrosamides, compounds that induce cancer in experimental animals, and possibly humans.17
The ascorbic acid content of pepper cultivars from several species is shown in Table 9.1.18–22 All the peppers referenced are excellent sources of ascorbic acid, with many of the cultivars contributing over 100% of the Recommended Daily Intakes (RDIs) in the U.S. The current RDI for vitamin C is 90 mg/d for adult men and 75 mg/d for adult women who are not pregnant or lactating. The only pepper cultivars that fail to meet at least 50% of the RDI for ascorbic acid are the chile-type cultivars NuMex RNaky, New Mexico, and B-18 at the green stage and the tabasco-type called cv tabasco at the green stage.
The ascorbic acid content of most of the pepper types increases during ripening, with much higher levels found in mature peppers at the final stage of ripening.23–26 Higher levels of ascorbic acid observed during ripening may be related to light intensity and greater levels of glucose, the precursor of ascorbic acid.27 Because total and reducing sugars increase during pepper fruit ripening, the elevated ascorbic acid levels in mature fruit may reflect greater synthesis due to the higher FIGURE 9.1 Ascorbic acid, flavonoids, and tocopherols in Capsicum fruit.
O
OH
OH O
HO
OH
O O
O O
HO
OH L-ascorbic acid L-dehydroascorbic acid
O
OH O OH O H
OH OH
O
O OH O H
OH OH
Quercetin Luteolin
O O
H
-tocopherol
O O
H
-tocopherol 6409_book.fm Page 167 Saturday, September 16, 2006 9:54 AM
168 Handbook of Nutraceuticals and Functional Foods
TABLE 9.1
Ascorbic Acid Content of Fresh Capsicum Fruit
Species Type Cultivar Maturity
mg/100 g Fresh Weight
%RDIa
Ref.
Male Female
C.annuum Ancho San Luis Ancho Green 168 187 224 18
Bell Dove White 77 86 103 18
Dove Light Orange 103 114 137 18
Ivory White 89 99 119 18
Ivory Light Yellow 110 122 147 18
Blue Jay Purple 95 106 127 18
Blue Jay Orange 123 137 164 18
Lilac Purple 67 74 89 18
Lilac Orange 104 116 139 18
Valencia Green 119 132 159 18
Valencia Orange 73 81 97 18
Oriole Green 91 101 121 18
Oriole Orange 86 96 115 18
Black Bird Green 66 73 88 18
Black Bird Black 62 69 83 18
Chocolate Beauty Green 62 69 83 18
Chocolate Beauty Brown 100 111 133 18
Cardinal Green 102 113 136 18
Cardinal Brown 124 138 165 18
King Arthur Green 84 93 112 18
King Arthur Red 87 97 116 18
Var. 862R Green 88 98 117 18
Var. 862R Red 98 109 131 18
Red Bell G Green 95 106 127 18
Red Bell G Red 96 106 127 18
Red Bell C Green 72 80 96 18
Red Bell C Red 107 119 143 18
Klondike Bell Green 112 124 149 18
Klondike Bell Yellow 109 121 145 18
Canary Green 112 124 149 18
Canary Yellow 108 120 144 18
Orobelle Green 162 180 216 18
Orobelle Yellow 95 106 127 18
Golden Bell Green 106 118 141 18
Golden Bell Yellow 90 100 120 18
Tam Bel-2 Green 109 121 145 20
Tam Bel-2 Red 148 164 197 20
Grande Rio-66 Green 98 109 131 20
Grande Rio-66 Red 149 166 199 20
Yellow Bell-47 Green 114 127 152 21
Yellow Bell-47 Orange 135 150 180 21
Cascabella Peto Cascabella Yellow 172 191 229 21
Peto Cascabella Red 202 224 269 21
Cayenne Mesilla Green 63 70 84 21
Mesilla Red 102 113 136 21
Chile New Mexico-6 Green 141 157 188 20
New Mexico-6 Red 205 228 273 20
New Mexico-6 Green 130 144 173 18
Antioxidant Vitamin and Phytochemical Content of Fresh and Processed Pepper Fruit 169
levels of sugar precursors.22 In addition to maturation, variation in ascorbic acid content between pepper types and cultivars may be attributed to differences in genetics, fertilization practices, and environmental growing conditions. The effects of fertilization on ascorbic acid content of peppers have been studied. Ascorbic acid content of pepper fruits increased with increasing levels of phosphorus up to 48 kg/ha, at varying levels of nitrogen (0 to 100 kg/ha),28 and applications including combinations of organic matter + nitrogen + phosphorus increased ascorbic acid content of capsicum fruit.29 Application of bioregulators may also affect ascorbic acid content of peppers.
Tam Mild Chile Green 155 172 207 20
Tam Mild Chile Red 233 259 311 20
Green Chile Green 122 136 163 18
Sandia Green 71 79 95 22
Sandia Breaker 220 244 293 22
Sandia Red 239 266 319 22
New Mexico 6-4 Green 40 44 53 22
New Mexico 6-4 Breaker 122 136 163 22
New Mexico 6-4 Red 155 172 207 22
NuMex RNaky Green 28 31 37 22
NuMex RNaky Breaker 145 161 193 22
NuMex RNaky Red 164 182 219 22
B-18 Green 15 17 20 22
B-18 Breaker 91 101 121 22
B-18 Red 186 207 248 22
Jalapeno Jalapeno-M Green 173 192 231 20
Jalapeno-M Red 179 199 239 20
Tam Veracruz Green 101 112 135 20
Tam Veracruz Red 144 160 192 20
Tam Veracruz Green 72 80 96 18
Tam Mild Green 66 73 88 18
Mitla Green 49 54 65 18
Jaloro Yellow 131 146 175 18
Sweet Jalapeno Green 54 60 72 18
Serrano Hidalgo Green 141 157 188 20
Hidalgo Red 263 292 351 20
Yellow Wax Hungarian Yellow Yellow 114 127 152 18
Long Hot Yellow Yellow 114 127 152 18
Gold Spike Yellow 115 128 153 18
Inferno Yellow 92 102 123 21
Inferno Red 138 153 184 21
Rio Grande Gold Red 243 270 324 20
Sante Fe Grande Red 187 208 249 20
C. chinense Habanero Red Savina Red 192 213 256 21
Francisca Orange 203 226 271 21
C. frutescens Tabasco McIhenny Tabasco Green 15 17 20 21
McIhenny Tabasco Red 75 83 100 21
a Recommended daily intakes, adult males = 90 mg/100 g, adult females = 75 mg/100 g.
TABLE 9.1 (Continued)
Ascorbic Acid Content of Fresh Capsicum Fruit
Species Type Cultivar Maturity
mg/100 g Fresh Weight
%RDIa
Ref.
Male Female 6409_book.fm Page 169 Saturday, September 16, 2006 9:54 AM
170 Handbook of Nutraceuticals and Functional Foods
The ascorbic acid and citric acid contents of “bell” peppers increased with gibberellic acid treat-ment,30 whereas in another study the ascorbic acid content of bell peppers was not affected by ethylene treatment.31