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Hideka Kobayashi, Changzheng Wang, and Kirk W. Pomper

fruit intake and the lower incidence of chronic diseases ( Ness and Powles, 1997 ; New et al., 2000 ). The chemoprotective properties of fruits have been partly attributed to phenolics such as gallic acid and chlorogenic acid, and the phenolic content

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Malkeet S. Padda and David H. Picha

Phenolic compounds and antioxidant activity were quantified in the principal sweetpotato cultivars marketed in the European Union. Total phenolic content, individual phenolic acids, and antioxidant activity in each cultivar were determined using Folin-Denis reagent, reversed-phase HPLC, and 1,1-diphenyl-2-picrylhydrazyl (DPPH) methods, respectively. Significant differences in phenolic composition and antioxidant activity were found between cultivars. A Jamaican-grown, white-fleshed cultivar had the highest total phenolic content [4.11 mg·g-1 chlorogenic acid (dry tissue weight)], while the highest antioxidant activity [3.60 mg·g-1 Trolox (dry tissue weight)] was observed in the orange-fleshed California-grown cultivar Diane. Chlorogenic acid and 3,5-dicaffeoylquinic acid were the predominant phenolic acids, while caffeic acid was the least abundant in most cultivars. The highest content of chlorogenic acid (0.42 mg·g-1 dry tissue weight); 3,5-dicaffeoylquinic acid (0.43 mg·g-1 dry tissue weight); and 3,4-dicaffeoylquinic acid (0.25 mg·g-1 dry tissue weight) was present in the white-fleshed Jamaican cultivar. The orange-fleshed cultivars Diane and Beauregard had the highest content of caffeic acid (0.13 mg·g-1 dry tissue weight) and 4,5-dicaffeoylquinic acid (0.32 mg·g-1 dry tissue weight), respectively.

Open access

Sylvia M. Blankenship and Daryl G. Richardson

Abstract

High performance liquid chromatography of mature ‘Beurre d'Anjou’ and ‘Beurre Bosc’ pear (Pyrus communis L.) fruit flesh showed that the major phenolics at harvest were chlorogenic acid, catechin, and arbutin. Neither cultivar contained epicatechin nor p-coumaroyl quinate. During 160 days at –1°C the chlorogenic acid content of d'Anjou increased significantly. In ‘Bosc’, chlorogenic acid levels decreased during storage. Catechin content increased linearly while arbutin levels remained nearly constant in both cultivars. Coincident with the completion of the cold requirement for initiation of ripening and endogenous ethylene production, i.e., 20 days for ‘Bosc’ and 50 days for ‘d'Anjou’, there was an appearance of low levels of a p-coumaric acid derivative and trace amounts of epicatechin/p-coumaroyl quinate. At 120 days epicatechin/p-coumaroyl quinate increased in ‘d'Anjou’ but not in ‘Bosc’. There is a coincidence, and perhaps relationship, between ethylene production and the quantity as well as the composition of phenolics present during storage. Bruising pear fruit after 120 days of storage caused a 30% increase in chlorogenic acid and a 50% increase in catechin, but no increase in p-coumaric acid derivatives.

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Francisco A. Tomás-Barberán, Julio Loaiza-Velarde, Antonio Bonfanti, and Mikal E. Saltveit

The phenolic composition of whole heads and excised midrib sections of iceberg, butter leaf, and romaine lettuce (Lactuca sativa L.) was followed at 5 and 10 °C during the first 3 days after wounding or during continuous exposure to 10 μL·L-1 ethylene in air. After 3 days of storage at 5 and 10 °C, only 5-caffeoylquinic acid (chlorogenic acid), 3,5-dicaffeoylquinic acid (isochlorogenic acid), caffeoyltartaric acid, and dicaffeoyltartaric acid were detected in wounded lettuce midribs. Of these four compounds, chlorogenic acid accumulated to the highest level in all three lettuce types. The content of caffeic acid derivatives increased 3- and 6-fold after 72 hours of storage at 5 and 10 °C, respectively. The synthesis of caffeoyltartaric acid was not induced by wounding in iceberg lettuce, while chlorogenic acid increased 5-fold at 5 °C and 10-fold at 10 °C. Similar relative phenolic compositions were detected in the three lettuce types studied, although at different concentrations. Changes observed in the content of individual phenolic compounds during the first 3 days of ethylene exposure seemed to follow the same pattern observed during wound induction of the synthesis of phenolic compounds. Chlorogenic acid increased 5-fold and isochlorogenic acid increased 10-fold, while the content of caffeoyltartaric derivatives were not significantly altered by ethylene treatment. Isochlorogenic acid, which was only present in low amounts in the control, was synthesized in the later steps of wound and ethylene induction. Similar kinetics for the induction of phenolic compounds were observed in the three lettuce types studied, suggesting that the mechanisms by which wounding induces phenylpropanoid synthesis are common for the different lettuce types.

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Guiwen W. Cheng and Carlos H. Crisosto

The formation of metallo-pigmentation and copigmentation as potential mechanisms of inking formation was investigated in peach and nectarine skin tissues. Cyanidin-3-glucoside, the most abundant anthocyanin in peaches and nectarines, formed very purple ferric complexes with an anthocyanin/iron molar ratio of two. Greenish metallo complexes between ferric ion and chlorogenic acid, caffeic acid, catechin, or epicatechin formed with an phenolic/iron molar ratio of one. The lack of copigmentation pointed out the importance to focus research on the metallo-phenolics reaction. High intensity of dark color formation was developed with cyanidin-3-glucoside, followed by caffeic acid, chlorogenic acid, catechin, and epicatechin on an equal molar basis. Citric acid acted as a strong iron chelator to prevent and reverse the formation of ferric cyanidin-3-glucoside complexes. The variety of dark and light colored spots observed on the surface of peaches and nectarines is explained by the formation of metallo-pigment complexes.

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M.S. Padda and D.H. Picha

Antioxidant activity and phenolic content in sweetpotato root and leaf tissues were quantified at different developmental stages. The 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical method was used to measure antioxidant activity and total phenolic content was quantified by spectrophotometry using Folin-Denis reagent. Individual phenolic acids were quantified using reversed phase high performance liquid chromatography. Antioxidant activity and phenolic content decreased with root development and leaf maturity. Roots at the initial stages of development (about 4 g root weight) had a higher antioxidant activity and phenolic content compared to fully developed roots. Phenolic content in fully developed roots was significantly higher in the cortex tissue than internal pith tissue. The highest total phenolic content and antioxidant activity was found in cortex tissue at the initial stage of development (10.3 mg chlorogenic acid eq/g dry tissue weight and 9.7 mg Trolox eq/gdry tissue weight, respectively). Sweetpotato leaves had a significantly higher phenolic content and antioxidant activity than roots. Immature unfolded leaves had the highest total phenolic content (88.5 mg chlorogenic acid eq/g dry tissue weight) and antioxidant activity (99.6 mg Trolox eq/g dry tissue weight). Chlorogenic acid was the major phenolic acid in root and leaf tissues with the exception of young immature leaves in which the predominant phenolic acid was 3,5-dicaffeoylquinic acid.

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M.S. Padda and D.H. Picha

Antioxidant activity and phenolic content of sweetpotato root and leaf tissues were quantified at different developmental stages. 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical method was used to measure antioxidant activity and total phenolic content was quantified by spectrophotometry using Folin-Denis reagent. Individual phenolic acids were quantified using reversed phase high performance liquid chromatography. Antioxidant activity and phenolic content decreased with root development and leaf maturity. Roots at the initial stages of development (about 4.0 g root weight) had a higher antioxidant activity and phenolic content compared to fully developed roots. Phenolic content in fully developed roots was significantly higher in the cortex tissue than internal pith tissue. The highest total phenolic content and antioxidant activity was found in cortex tissue at the initial stage of development (10.3 mg chlorogenic acid eq/g dry tissue weight and 9.7 mg Trolox eq/gdry tissue weight, respectively). Sweetpotato leaves had a significantly higher phenolic content and antioxidant activity than roots. Immature unfolded leaves had the highest total phenolic content (88.5 mg chlorogenic acid eq/g dry tissue weight) and antioxidant activity (99.6 mg Trolox eq/g dry tissue weight). Chlorogenic acid was the major phenolic acid in root and leaf tissues with the exception of young immature leaves in which the predominant phenolic acid was 3,5-dicaffeoylquinic acid.

Open access

P.D. Lidster, A.J. Dick, A. DeMarco, and K.B. McRae

Abstract

Vacuum infusion or dipping fruit in solutions of an apple (Malus domestica Borkh.) extract containing chlorogenic acid, catechins, and quercetin glycosides (isolated from ‘Spartan’ apples) suppressed fruit softening of ‘Spartan’ and ‘Golden Delicious’ apples held at 20°C. Quercetin or rutin [0.01% or 0.05% (w/v)], applied by postharvest vacuum infusion or dipping, reduced softening of ‘Golden Delicious’ apples held at 20° and 0°. Structurally related compounds (catechin, coumaric acid, and chlorogenic acid) showed some potential for retarding fruit softening but the effects were inconsistent. Additions of 0.25% (w/v) thickener plus 0.1% surfactant to the dipping solution containing the above compounds further reduced fruit firmness loss in storage. When quercetin or rutin were vacuum-infused either before or after CA storage, fruit were firmer than control fruit over a 25-day period at 20°.

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Ki-Cheol Son, Ray F. Severson, Maurice E. Snook, and Stanley J. Kays

Methanol extracts of external (outer 3 mm) and interior root tissue of four sweetpotato [Ipomoea batatas (L.) Lam.] cultivars (`Centennial', `Jewel', `Regal', and `Resisto') having different levels of susceptibility to the sweetpotato weevil [Cylas formicarius elegantulus Summer] were analyzed for simple carbohydrates (fructose, glucose, sucrose, inositol) and organic acids (malic, citric, quinic) by gas chromatography and for phenolics (caffeic acid, caffeoylquinic acids, rutin) by high-performance liquid chromatography. There were significant differences among cultivars in the concentrations of total sugars and phenolics in the external tissue (P < 0.05). In addition, the distribution of carbohydrates, organic acids, and chlorogenic acid [3-O-caffeoylquinic acid] differed between external and interior tissues. Sucrose was the major water-soluble carbohydrate in all cultivars. With the exception of malic acid, the concentration of carbohydrates, organic acids, and phenolics did not correlate with cultivar susceptibility to the sweetpotato weevil.

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Vicky W. Lee, H.P. Vasantha Rupasinghe*, and Chung-Ja Jackson

Apples are excellent sources of dietary phenolics, in particular flavonoids and chlorogenic acid, which are potent antioxidants that may play important roles in the prevention of chronic diseases. This study investigated the major phenolics profiles of apple fruit in relation to (1) the distribution among 8 Ontario-grown cultivars, (2) the different fruit parts, and (3) the effect of processing of fresh-cuts. In addition, total antioxidant capacity (TAC) and total phenols content (TPC) were measured in apples by spectrophotometric assays. Flavonoids and chlorogenic acid were quantified using HPLC/PDA. Vitamin C was quantified using HPLC/Fluorescence. TAC, TPC and flavonoids levels were the highest in Honey Crisp and Delicious, moderate in Idared, Spartan, Granny Smith, and Cortland, and the lowest in Crispin and Empire. Apple peel contained 2 to 10-fold higher TAC, TPC and total of 10 major phenolics than that of core and flesh indicating peeling of apples during processing could reduced significantly the nutritional quality of fresh-cut apples. Dihydrochalcone (phloridzin) and chlorogenic acid levels were 2 to 21-fold higher in apple core than skin and flesh. TAC levels and vitamin C contents could be increased up to 3-fold and 14 to 20-fold, respectively by the post-cut dipping treatment with an ascorbic acid-based antioxidant formula. The phenolic profiles of sliced apples were stable up to 21 days at 4°C.