Showing report on Fruits and fruit products
Berries are small fruits produced by various botanical species. The most widely consumed berries belong to the Ericaceae and Rosaceae families. The polyphenolic profiles are principally documented for berries belonging to the genus Vaccinium (blueberry and cranberry), Ribes (blackcurrant, redcurrant, gooseberry), Rubus (blackberry and raspberry), and Fragaria (strawberry). Two types of blueberries can be distinguished: the highbush blueberry (Vaccinium corymbosum L.) and the lowbush blueberry (Vaccinium angustifolium Aiton). Cranberries are classified as lingonberry (Vaccinium vitis-idaea L.), American cranberry (Vaccinium macrocarpon Aiton), and European cranberry (Vaccinium oxycoccus L). The other species are blackcurrant (Ribes nigrum L.), redcurrant (Ribes rubrum L.), gooseberry (Ribes uva-crispa L.), blackberries (Rubus spp.), cloudberry (Rubus chamaemorus L.), red raspberries (Rubus idaeus L.), black raspberry (Rubus occidentalis L.), and strawberry (Fragaria x Ananassa). Bilberry (Vaccinium myrtillus L.), bog bilberry (Vaccinium uliginosum L.), evergreen huckleberry (Vaccinium ovatum Pursh), black crowberry (Empetrum nigrum L. agg), rowanberry (Sorbus aucuparia), black chokeberry (Aronia melanocarpa), sea-buckthorn berry (Hippophae rhamnoides L.), and black elderberry (Sambucus nigra) are less studied but some of them are rich in polyphenols.
The polyphenol content (Folin assay) in berries may vary from 30 to 2000 mg/100 g. The highest levels are found in black elderberry (1950 mg/100 g), black chokeberry (1752 mg/100 g), black raspberry (980 mg/100 g), and blackcurrant (821 mg/100 g). A wide range of phenolic compounds are present in berries and polyphenol profiles are characteristic of each species (70). The main polyphenols in berries are the anthocyanins, the ellagitannins (Rubus and Fragaria genus), and the proanthocyanidins. Because of their polymeric nature and complex molecular structures, ellagitannins and proanthocyanidins are difficult to quantify and could be underestimated. Phenolic acids and flavonols are less abundant and less studied, except in some species such as blueberries rich in 5-caffeoylquinic acid.
The content of total anthocyanins (sum of individual anthocyanins as measured by chromatography) varies widely between species. The highest levels are found in black elderberry (1317 mg/100 g), black chokeberry (878 mg/100 g), and blackcurrant (592 mg/100 g). In black raspberry, evergreen huckleberry and bilberry there are no quantitative data available for the individual anthocyanins, but high levels are reported with the pH differential method (589 mg/100 g, 408 mg/100 g and 299 mg/100 g). Intermediate levels of anthocyanins are found in lowbush blueberry (187 mg/100 g), higbush blueberry (134 mg/100 g), and blackberry (173 mg/100 g). The lowest levels are found in strawberry (73 mg/100 g), red raspberry (71 mg/100 g), cranberries (60 mg/100 g in lingonberry and 50 mg/100 g in American cranberry), gooseberry (6.6 mg/100 g), and cloudberry (3.4 mg/100 g).
Most berries possess simple anthocyanin profiles and at least 80% of the total anthocyanins is represented by a limited number of compounds, except in blueberries, bilberries, and huckleberries where more complex profiles are observed. Anthocyanins in berries are principally glycosides of cyanidin, delphinidin, peonidin, pelargonidin, malvidin and petunidin. They are glycosylated with glucose, galactose, arabinose or rutinose, and to a lesser extent with xylose as in chokeberry, sambubiose as in elderberry, and sophorose as in raspberry.
Cyanidin is the most common anthocyanidin. It is generally found as cyanidin 3-O-glucoside. The highest levels of cyanidin derivatives are found in black elderberry (1315 mg/100 g) and black chokebery (876 mg/100 g). Cyanidin derivatives are the major anthocyanins in black elderberry (glucoside and sambubioside), black chokeberry (galactoside and arabinoside, xyloside and glucoside), blackberry (glucoside), red raspberry (sophoroside), and lingonberry (galactoside). The main anthocyanin in black raspberry is cyanidin 3-(6’-p-coumaroyl)-glucoside (71).
The highest levels of delphinidin derivatives are found in blackcurrant (392 mg/100 g) while the highest levels of peonidin derivatives are found in American cranberry (36 mg/100 g). Pelargonidin is principally found in strawberry and is mainly present as pelargonidin 3-O-glucoside and pelargonidin 3-O-(6’’-succinyl-glucoside) (total 58 mg/100 g). The anthocyanins in strawberry were characterised by LC using DAD and ESI-MS and 15 compounds were identified (72).
A more complex anthocyanin profile is found in blueberries. Twenty-five different anthocyanins were identified in highbush and lowbush blueberries (73). Polyphenol content is generally higher in lowbush than in highbush blueberries (73, 74). The major anthocyanins in blueberries are conjugated forms of malvidin (respectively 76 and 48 mg/100 g in lowbush and highbush blueberry), delphinidin (46 mg/100 g in both lowbush and highbush blueberry), petunidin (29 mg/100 g in both lowbush and highbush blueberry) and cyanidin (respectively 24 and 9.9 mg/100 g in lowbush and highbush blueberry). Some acetylated anthocyanins have been detected in lowbush and highbush cultivars (73, 75) but are absent in others (73, 75, 76, 77).
Proanthocyanidin dimers and trimers have been quantified by chromatography but are only present in low quantities. The polymers are difficult to separate and their exact content in berries remains a matter of debate. Direct phase HPLC methods showed that the main forms present in berries are those with highest degree of polymerization (>10mers and 4-10 mers), except in elderberry, blackberry and raspberry where these forms are quasi-absent (75, 78, 79). All berries contain B-type proanthocyanidins but A-type proanthocyanidins with doubly-linked flavanol units are also found in cranberry. The hydroxylation pattern of proanthocyanidins varies according to species: procyanidins are found in all the berries studied, propelargonidin in strawberry and raspberry, and prodelphinidin in blackcurrant, redcurrant and gooseberry. The highest levels of proanthocyanidins (direct phase) are found in black chokeberry (659 mg/100 g) and lowbush blueberry (330 mg/100 g). Cranberry also contains high contents of proanthocyanidins (411 mg/100 g) but because of a lack of information on the species, these data were not shown in the composition table. Lower contents are found in highbush blueberry (176 mg/100 g), strawberry (141 mg/100 g), blackcurrant (137 mg/100 g), gooseberry (81 mg/100 g) and redcurrant (59 mg/100 g).
Ellagitannins are esters of hexahydroxydiphenic acid and a polyol, usually glucose or quinic acid. When exposed to acids or bases, ester bonds are hydrolysed and the hexahydroxydiphenic acid spontaneously rearranges into the water-insoluble ellagic acid (80). Ellagitannins are characteristic of the Rubus (raspberries and blackberries) and Fragaria (strawberries) genera. The highest quantities are found in red raspberry, cloudberry, and strawberry (81, 82). Red raspberry contains sanguiin H6 (81 mg/100 g) and lambertianin C (36 mg/100 g). Sanguiin H10 was also identified but not quantified (83). There are no quantitative data available for the other berries. High contents of free ellagic acid were quantified in blackberry (44 mg/100 g), black raspberry (38 mg/100 g) and cloudberry (15 mg/100 g). Lower amounts of glycosylated ellagic acid are also present in red raspberry (2.8 mg/100 g) and strawberry (2.9 mg/100 g).
Berries also contain hydroxycinnamic acids. High levels of free caffeic acid are found in black chokeberry (141 mg/100 g). Highbush and lowbush blueberries contain respectively 131 and 87 mg/100 g 5-caffeoylquinic acid. High levels of 5- and 3-caffeoylquinic acid were also found in rowanberry juice (respectively 54 and 27 mg/100 ml). High levels of total hydroxycinnamic acids were also reported in the fruit (679 mg/100 g DW) (81). Most hydroxycinnamic acids are present in berries as esters and glycosides (84).
The highest flavonol quantities are found in black chokeberry (88 mg/100 g), black elderberry (42 mg/100 g), highbush blueberry (39 mg/100 g), lingonberry (31 mg/100 g), and American cranberry (28 mg/100 g). High quantities were also quantified in sea-buckthorn berry juice (85), as well as bog bilberry, European cranberry, rowanberry and black crowberry (81). The most abundant flavonols in berries are glycosides of quercetin and to a lesser exent myricetin and isorhamnetin.
Citrus fruits contain high amounts of flavanone glycosides (hesperidin, narirutin and didymin), lower amounts of polymethoxylated flavones, and traces of flavonols and hydroxycinnamic acids. Blood orange also contains anthocyanins. The nature of polyphenols differs according to citrus species (86). Major polyphenols in orange (Citrus sinensis) and tangerine (Citrus reticulata) are hesperidin, narirutin and didymin, in grapefruit (Citrus paradisi) naringin and narirutin, and in lemon (Citrus limon) hesperidin and eriocitrin.
Flavanones are more concentrated in albedo and membranes than in juice sacs, respectively 13000, 11000-27000 and 380 ppm of naringin in grapefruit (87). Due to the high weight of segments (97.5% of the orange edible parts), albedo and the segments contribute for similar quantities of flavanones when consuming a fruit (100 mg from segments and 88 mg from albedo for a Navelina orange) (88).
Due to the high concentration of flavanones in the fruit membranes, the consumption of one fruit should provide more polyphenols than the consumption of the juice produced from the same fruit. However the paucity of data on polyphenol content in citrus fruits does not allow seeing it in the composition table.
For juice, extraction methods used for analysis influence flavanone content values (89, 90, 91). Analyses are sometimes carried out after centrifugation and filtration. This results in the loss of the polyphenols contained in the cloud fraction. To have a more complete extraction of flavanones poorly soluble in water, some authors have added DMF or DMSO to the extraction slurry of fruits or to the cloudy juice. This results in significantly higher content values. In fresh juices, the flavanones extracted by DMSO from the cloudy fraction account for 14% of the total (92). In commercial juices, the flavanones present in a soluble form in the filtered juice are partly precipitated upon storage. Therefore flavanones present in the cloudy fraction of commercial juice account for 14 to 85% of the total flavanones (92). Individual content values in the database were all aggregated without considering the differences in extraction methods.
Composition data from the tables allow determining the quantity of polyphenols provided per serving. A bottle of fresh orange juice (250 ml) contains 65 mg hesperidin, 13 mg narirutin and 15 mg didymin. Based on only one reference, the content values for tangerine juice are close to those found in orange. A bottle of blood orange juice (250 ml) also contains about 105 mg anthocyanins. A bottle of fresh grapefruit juice (250 ml) contains 77 mg naringin and 24 mg narirutin.
The variations of flavanone and anthocyanin contents according to cultivars have been studied by different authors. No significative differences were found for flavanones in orange (93, 94, 95). More variations were observed for anthocyanins in blood oranges, with the Moro cultivar being the richest as compared to Sanguinello and Tarocco (96).
Storage may also affect the content of flavanones. When citrus juices and segments are cold-stored at 4°C for 12 days, total flavonoids decreased (x 1/2) in juices and increased (x 2) in segments (97). For anthocyanins in blood orange, a large decrease (x 1/5) has been reported when the juices where stored at 20°C (98). Howewer, other authors did not observe any degradation in similar conditions (99).
Processing also influences content values. Commercial squeezing of Navel orange extracted 22% more phenolics than hand squeezing. Freezing of juice caused a dramatic decrease in polyphenols, whereas the concentration process only caused a mild precipitation. Pasteurization of pulp (obtained after squeezing and centrifugation of the juice) led to the degradation of several phenolic compounds but had not effect on juice (100).
Pomes (apple, pear and quince) and drupes (apricot, cherry, peach and nectarine, plum) contain chlorogenic acids, anthocyanins, flavonols, catechins and proanthocyanidins.
Hydroxycinnamic acid esters are dominant in pomes and drupes. The 5-caffeoylquinic acid (chlorogenic acid) is universally present, the 3-caffeoylquinic acid (neochlorogenic acid) is abundant in plums and cherries, the 4-caffeoylquinic acid (cryptochlorogenic acid) is abundant in plum, the 3-p-coumaroylquinic acid is abundant in cherry, and the 3,5-dicaffeoylquinic acid is only reported in quince.
Anthocyanins are abundant in cherries and plums. Cyanidin 3-O-rutinoside is the main anthocyanin in sweet cherry and plum, while it is cyanidin 3-O-glucosyl-rutinoside in sour cherry.
Proanthocyanidins are detected in pomes and drupes, however only few studies are available. The highest proanthocyanidin contents estimated by direct phase HPLC are found in plum (richest than apple), while the lowest contents are found in cherry (polymers >10 are not detected). No data for quince are given (78). The mains reported catechins are (+)-catechin and (-)-epicatechin.
Low quantities of flavonol glycosides, mainly quercetin and kaempferol glycosides, are found in skins and are scarce in fleshes.
Apple (Malus domestica) contains catechins, procyanidins, hydroxycinnamates and flavonols. It also contains low amounts of dihydrochalcones. The main individual compounds are (-)-epicatechin, (+)-catechin, procyanidin dimer B2, 5-caffeoylquinic acid, several quercetin glycosides and phloridzin, a dihydrochalcone glucoside characteristic of apple. Cider apples differ from dessert apples by their relatively high content of procyanidins responsible for their astringency and bitterness (101).
Distribution of polyphenols in the fruit differs according to polyphenol type. Flavonols are largely restricted to the skin (102, 103, 104). The skin of red apples also contains anthocyanins (105). Most other polyphenols are present in both the flesh and skin of the fruit. Flesh, due to its high relative weight, is the main contributor to the intake of these polyphenols even if the concentrations in the skin are often higher (except for chlorogenic acid) (106, 107, 108). Phloridzin is particularly abundant in the seeds where it represents 98% of flavonoids. Phloridzin in seeds is 10 time more concentrated than in skin and 100 time more than in flesh (106).
Apple polyphenols are generally estimated by HPLC without hydrolysis. Flavonol glycosides have also been estimated after acid hydrolysis as aglycones. Procyanidins are present as mixtures of oligomers with varying degrees of polymerization (DP). Dimers and trimers are commonly analysed by reverse phase HPLC (109). Oligomers up to decamers can be analysed by direct phase HPLC (78). Total procyanidins have also been analysed by HPLC after thiolysis (110).
Catechins and procyanidins are not galloylated. The major flavonol is quercetin together with low amount of kaempferol and myricetin. They are largely present as glycosides. 5-Caffeoylquinic acid (chlorogenic acid) is the main phenolic acid.
The proportion of the polyphenol classes varies greatly from one apple cultivar to another (111, 112, 113). The total polyphenol concentration varies from 1 to 7 g/kg of fresh cortex, and cider varieties show a higher polyphenol concentration than dessert apples (114). Crop load is also an important parameter and a decrease of crop load from 157 to 30 fruits per crown results in an increase of total polyphenol content of fruit (+29%), as well as of the concentrations of the most important individual polyphenols (115). In addition, it was shown that the levels of anthocyanins, quercetin glycosides and total flavonoids are highest in fruit born in the top part of the crown (106). Phloridzin and chlorogenic acid contents were not affected by the position of the fruit in the tree. Sun exposure results in an increase of cyanidin 3-O-galactoside and quercetin 3-O-glycoside contents in the skin, but had no effect on phloridzin, (+)-catechin, and chlorogenic acid (106).
The concentrations of individual polyphenols in apple flesh decrease sharply during the early stage of development and remain relatively constant during maturation and storage (107). A 6-month cold-storage of fruits results in minor changes in (+)-catechin, phloridzin, chlorogenic acid, cyanidin 3-O-galactoside and quercetin glycoside contents (106). However, it was also reported that a 6-month storage of apples at 5°C results in a decrease of the Folin values from 2165 mg/kg to 1470 mg/kg (116).
Average polyphenol contents in whole dessert apple are as follows: 8.3 mg/100 g (-)-epicatechin, 6.8 mg/100 g quercetin glycosides, 101.4 mg/100 g procyanidins (direct phase) and 13.2 mg/100 g chlorogenic acid. Peeled dessert apple contains 6.7 mg/100 g (-)-epicatechin, 0.5 mg/100 g quercetin glycosides, 84.0 mg/100 g procyanidins (direct phase), and 18.2 mg/100 g chlorogenic acid. Whole cider apple contains 5.7 mg/100 g quercetin glycosides. There are no data for the others compounds. Peeled cider apple contains 28.7 mg/100 g (-)-epicatechin, 0.3 mg/100 g quercetin glycosides, and 49.3 mg/100 g chlorogenic acid.
Apple polyphenols are not all recovered in juice. Most of the polyphenols are retained in the pomace. Only about 10% of the flavonols, 3% of catechins and 50% of chlorogenic acid present in the fruit were recovered in the juice (103, 117). According to aggregation data, pure juice of dessert apple contains 7.8 mg/100 ml (-)-epicatechin, 1.4 mg/100 ml quercetin glycosides, and 7 mg/100 ml chlorogenic acid. Juice from concentrate of dessert apple contains 0.03 mg/100 ml (-)-epicatechin, 0.09 mg/100 ml quercetin glycosides, and 3.0 mg/100 ml chlorogenic acid. Pure juice of cider apple contains 9.0 mg/100 ml (-)-epicatechin and 21.5 mg/100 ml chlorogenic acid. Juice from concentrate of cider apple contains 3.7 mg/100 ml chlorogenic acid. Overall, the contents of all polyphenols are significantly lower in juices from concentrates than in pure juices.
Clarification treatments used in juice manufacture significantly differ in their effects on the phenolic composition of final apple juice, and the extent of polyphenol loss varies from 3.8% to 58.6% (118). Storage of 7 commercial apple juices for 11 months at room temperature also resulted in a decrease of phenolic acids (5% to 20%) and flavonoids (8% to 19%) (119).
In pear (Pyrus communis), the main quantified compounds are 5-caffeoylquinic acid (11.3 mg/100 g and 3.2 mg/100 g for respectively whole and peeled pear) and (-)-epicatechin (3.8 mg/100 g and 1.4 mg/100 g for respectively whole and peeled pear). Several quercetin and isorhamnetin 3-O-glycosides were additionaly identified (120). Pear also contains small amounts of arbutin (0.05 and 1.40 mg/100 g for respectively whole and peeled pear), considered as a chemical marker. Anthocyanins are found in the peel of colored cultivars (121). Only low levels of proanthocyanidins are quantified in pear (78). However, they are likely to account for a non-negligible part of the total polyphenols with 96% of total polyphenols in the pulp of a Portuguese pear (122).
Storage of concentrates for 9 months at 25°C resulted in approximately 50-60% degradation of cinnamic acids in all the juices and complete procyanidin oxidation. Enzymatic clarification, bottling, and concentration resulted in procyanidin loss, while fining resulted in no apparent procyanidin changes (123).
Because of the acidity, astringency, and toughly of the fresh fruit, quince (Cydonia Oblonga Miller) is usually consumed peeled as jam or jelly. The same compounds are found in processed and unprocessed fruits. The main polyphenols in quince are 3-caffeoylquinic acid (3.7 mg/100 g in fruit, 1.4 mg/100 g in jam and 0.4 mg/100 g in jelly), 4-caffeoylquinic acid (0.5 mg/100 g in fruit, 0.6 mg/100 g in jam and 0.2 mg/100 g in jelly), 5-caffeoylquinic acid (8.6 mg/100 g in fruit, 3.4 mg/100 g in jam and 1.3 mg/100 g in jelly) and 3,5-dicaffeoylquinic acid (0.6 mg/100 g in fruit and 0.4 mg/100 g in jam). The peels contain the same caffeoylquinic acids, several flavonol glycosides (quercetin 3-O-galactoside, kaempferol 3-O-glucoside, kaempferol 3-O-rutinoside) and several unidentified compounds (kaempferol glycoside, and quercetin and kaempferol glycosides acylated with p-coumaric acid) (124).
In comparison with jams, commercial and home-made jellies presented lower concentrations of the different phenolic compounds, with the exception of procyanidins (125). Arbutin was identified in commercial but not in home-made quince jam, which could be an adulteration with apple (126). Owing to duplicated amounts, and different phenolic profiles between jam with skin and jam without skin, adulterations with peel could be detected (127).
The major phenolic compounds found in apricot (Prunus armeniaca L.) are 3-caffeoylquinic acid (5.4 mg/100 g in fruit), 5-caffeoylquinic acid (3.4 mg/100 g in fruit and 2.9 mg/100 g in jam), (-)-epicatechin (4.6 mg/100g in fruit and 0.5 mg/100 g in jam) and (+)-catechin (3.9 mg/100 g in fruit and 0.4 mg/100 g in jam). Apricot contains low quantities of proanthocyanidins (12.9 mg/100 g estimated by direct phase HPLC). The main flavonols are quercetin 3-O-rutinoside and kaempferol 3-O-rutinoside (total 1.72 mg/100 g in fruit and 1.06 in jam). Protocatechuic acid, naringenin 7-O-glucoside (prunin) and quercetin 3-O-glucoside were identified but not quantified (128).
Processed and unprocessed apricots share similare qualitative profiles but lower quantities are found in processed products.
Sweet cherries (Prunus avium L.) and sour cherries (Prunus cerasus L.) contain principally anthocyanins and hydroxycinnamic acids esters. Anthocyanins in sweet cherry are glucosides and rutinosides of cyanidin, pelargonidin and peonidin. Cyanidin 3-O-rutinoside (143.3 mg/100 g) represents 84% of the total anthocyanins. Cyanidin 3-O-glucoside (18.7 mg/100 g) is the second most important anthocyanin in sweet cherry. In sour cherry, the anthocyanin profile is slightly different. Cyanidin 3-O-glucosyl-rutinoside, cyanidin 3-O-sophoroside, cyanidin 3-O-arabinosyl-rutinoside and cyanidin 3-O-gentiobioside are found in sour cherries but not in sweet cherries (129, 130). Cyanidin 3-O-glucosyl-rutinoside (43.7 mg/100 g) represents 80% of the total anthocyanins in sour cherry. The same hydroxycinnamic esters are found in sweet and sour cherry: 3-caffeoylquinic acid (44.7 mg/100 g in sweet cherry and 19.1 mg/100 g in sour cherry) and 3-p-coumaroylquinic acid (38.4 mg/100 g in sweet cherry and 14.0 in sour cherry). Flavonols were characterised in sour cherries, but not quantified (131). Proanthocyanidin polymers >10 were not detected in cherry (78).
During cherry maturation, total hydroxycinnamic acid content decrease while total anthocyanin content increase (132).
During storage, anthocyanins are degradated. During cool storage at 1°C for 15 days, cyanidin 3-O-rutinoside was halved and cyanidin 3-O-glucoside was reduced five times (133). During frozen storage at -23°C, 66% anthocyanins were degradated after 3 months and 87% after 6 months. Frozen storage at -70°C resulted in much greater anthocyanin stability with 90% remaining after 3 months and 88% after 6 months.
Total polyphenol also decreased, but not as extremely as anthocyanins (129, 130). Canning resulted in approximately 50% transfer of anthocyanins and total polyphenols from the fruits into the syrup. Samples show an apparent slight increase in total anthocyanin content with canning. After 5 months of storage at 22°C, a significant decrease in total anthocyanins was observed, although there was no significant decrease in total polyphenols at either 2°C or 22°C (129, 130). With brining, 50% of the anthocyanins and total polyphenols were leached from the cherries into the brine solution (129, 130).
Peaches (Prunus persica) and nectarines (a cultivar group of peach) possess similar qualitative and quantitative phenolic profiles (134). Major compounds in peach and nectarine are 5-caffeoylquinic acid (15.6 mg/100 g in whole peach, 5.3 mg/100 g in peeled peach, 6.1 mg/100 g in whole nectarine, 8.2 mg/100 g in peeled nectarine), 3-caffeoylquinic acid acid (8.8 mg/100 g in whole peach, 4.1 mg/100 g in peeled peach, 4.0 mg/100 g in whole nectarine, 5.1 mg/100 g in peeled nectarine), (-)-epicatechin (not dectected in whole peach, 8.0 mg/100 g in peeled peach, not dectected in whole nectarine, 3.0 mg/100 g in peeled nectarine), (+)-catechin (2.3 mg/100 g in whole peach, 5.5 mg/100 g in peeled peach, 4.7 mg/100 g in whole nectarine, 4.8 mg/100 g in peeled nectarine) and procyanidin dimer B1 (25.8 mg/100 g in peeled peach, 10.0 mg/100 g in whole nectarine, 13.1 mg/100 g in peeled nectarine). Although no composition data are shown in the table, proanthocyanidins were identified in peach (78, 135). The peel contains minors compounds such as malvidin 3,5-O-diglucoside (malvin), quercetin 3-O-rutinoside (rutin), and quercetin 3-O-glucoside (isoquercitrin) (136). Quercetin 3-O-rutinoside and quercetin 3-O-glucoside were present in whole nectarine (136), while they were not detected in peeled peach and nectarine (134, 136).
During ripening, the contents of 5-caffeoylquinic acid, 3-caffeoylquinic acid, (+)-catechin, procyanidin dimer B3, and caffeic acid decreased (137). During storage, the total polyphenol increased (138), while a canning at room temperature for 3 months resulted in a 30-43% loss in total polyphenols (138) and in a loss in higher oligomers (135).
The main compounds in plum (Prunus domestica) and dried plum or prune are caffeoylquinic acids isomers. 3-Caffeoylquinic acid (75.1 mg/100 g in fresh plum and 125.9 mg/100 g in prune) predominates. 4-Caffeoylquinic acid (1.4 mg/100 g in fresh plum and 31.2 mg/100 g in prune) and 5-caffeoylquinic acid (8.3 mg/100 g in fresh plum and 18.5 mg/100 g in prune) are present in lower quantities. Cyanidin 3-O-rutinoside (34.5 mg/100 g in fresh plum) is the main anthocyanin, with lower amounts of cyanidin 3-O-glucoside and peonidin 3-O-rutinoside. Quercetin 3-O-rutinoside (6.7 mg/100 g in fresh plum) is the main flavonol. Plum is also rich in proanthocyanidins (227.4 mg/100 g estimated by direct phase HPLC), which represent 70% of total polyphenols. In commercial dried plums, 42 compounds (essentially hydroxycinnamic acids) were determined by LC/MS/MS (139). In prune and prune juice, anthocyanins were not detected (140).
The contents found in prune are expectively higher than in fresh plum. However the compounds in plum are degraded during drying, and the anthocyanins are particularly affected. The polyphenols contents are halved in commercial prune compared to fresh plum (140). Hydroxycinnamic acids, (+)-catechin and quercetin 3-O-rutinoside were slowly degraded as a function of drying time, while anthocyanins disappeared very rapidly (141). Anthocyanins and flavonols disappeared proportionally to the temperature and this was independent of polyphenol oxidase (PPO) activity (142). The use of model solutions showed that anthocyanin degradation was dependant on the presence of quinines (143). During prune storage, anthocyanins disappeared in the 1st month of storage (144).
Tropical fruits are the fruits produced in tropical and subtropical countries (Far East, Latin America, Caribbean, Africa). They are called ‘exotic fruits’ in the countries where they are imported. Mango (Mangifera indica L.), banana (Musa sapientum L.), pineapple (Ananas comosus L. Merr.) and papaya (Carica papaya L.) are the dominant tropical varieties produced worldwide. Custard apple (Annona reticulata L.), guava (Psidium guajava L.), kiwi (Actinidia chinensis Planch), lichee (Litchi chinensis L.), longan (Euphorian longana Lam.), loquat (Eriobotrya japonica Lindl.), medlar (Mespilus spp.), passion fruit (Passiflora edulis L.), persimmon (Diospyros kaki L.), pomegranate (Punica granatum L.) and star fruit (Averroha carambola L.) are the other species available in the database.
Total polyphenol contents (Folin assay) in tropical fruits range from 15 mg/100 g in longan to 143 mg/100 g in star fruit. The highest quantities of polyphenols are found in guava (126 mg/100 g), kiwi (116 mg/100 g), loquat (116 mg/100 g) and mango (104 mg/100 g). Among the other major tropical fruits, banana, pineapple and papaya contain respectively 78, 61 and 58 mg/100 g polyphenols. Some juices and more particularly pomegranate juice with a content of 204 mg/100 ml are rich in polyphenols. Lower contents are found in pineapple commercial juice (42 mg/100 ml) and pineapple pure juice (36 mg/100 ml). In pomegranate pure juice, which also contains anthocyanins and ellagic acid derivatives, the gallotannin punicalagin was quantified in high quantities (44 mg/100 ml). Loquat is rich in cinnamic acids and contains 55 mg/100 g 5-caffeoylquinic acid.
Few data exist on the content of individual polyphenols in tropical fruits. Flavanols and proanthocyanidins are the main documented classes, and low values are generally reported for these compounds. The Folin values are much higher than the sum of the contents of individual compounds, most likely due to the lack of data on individual compounds, but also due to the presence of other reducing compounds such as ascorbic acid interfering with the Folin assay. Several phenolic compounds such as procyanidin oligomers and polymers up to heptadecamers, and glycosides of luteolin, quercetin and apigenin have been identified in the date but not quantified (145). In longan seeds, pulp and peel, the major components identified are gallic acid, corilagin (an ellagitannin) and ellagic acid (146). In mango, several gallotannins were identified in kernel, peel and pulp (147, 148), but only small amounts (0.2 mg/g DW) were found in the pulp (147). Guava contains apigenin and myricetin, respectively 58 and 55 mg/100 g DW estimated after hydrolysis (149).