Polyphenol composition of plum selections in relation to total antioxidant capacity.

Dietary polyphenols are associated with protection against chronic diseases such as cardiovascular disease. Pharmacological studies show a range of bioactivities and efficacy attributable to specific polyphenols. While many fruits are rich in polyphenols, wide cultivar variation of polyphenol composition is common. Our objective was to determine the composition of major bioactive polyphenols in 29 prevarietal selections of Western Australian plums, and Black Amber as an evaluation in developing breeding tools to develop fruit that may have enhanced health-promoting capacities. Total phenolics were quantified colorimetrically; selected polyphenols were quantified by HPLC; and the total antioxidant capacity (TAC) was measured by the antioxidant inhibition of oxygen radicals (AIOR) assay. Total phenolic concentration was significantly correlated with TAC (R = 0.95, P < 0.01). Neo-chlorogenic acid and quercetin glycosides were found to be the predominant polyphenols (mean 29.9 mg·kg(-1) and 50.7 mg·kg(-1), respectively). No significant correlations were found between the composition of predominant polyphenols in plums and the TAC. We argue that the value of in vitro TAC assays to breeding programs may be limited, and future research should focus on the heritability of known bioactive polyphenols.

Impact of postharvest disease control methods and cold storage on volatiles, color development and fruit quality in ripe 'kensington pride' mangoes.

Postharvest diseases of mango fruit (Mangifera indica L.) cause economic losses during storage and can be controlled by chemical, physical, or biological methods. This study investigated the effects of different physical and/or chemical disease control methods on production of volatiles, color development and other quality parameters in ripe 'Kensington Pride' mango fruit. Hard mature green mango fruit were harvested from an orchard located at Carnavon, Western Australia. The fruit were heat-conditioned (8 h at 40 +/- 0.5 degrees C and 83.5 +/- 0.5% RH), dipped in hot water (52 degrees C/10 min), dipped in prochloraz (Sportak 0.55 mL x L(-1)/5 min), dipped in hot prochloraz (Sportak 0.55 mL x L(-1) at 52 degrees C/5 min), dipped in carbendazim (Spin Flo 2 mL x L(-1)/5 min), and dipped in hot carbendazim (Spin Flo 2 mL x L(-1) at 52 degrees C/5 min). Nontreated fruit served as control. Following the treatments, the fruit were air-dried and kept in cold storage (13 +/- 0.5 degrees C) for three weeks before being ripened at 21 +/- 1 degrees C. The ripe pulp of the fruit that was treated with hot prochloraz or carbendazim at ambient and high temperatures showed enhanced concentrations of volatiles, while heat conditioning and hot water dipping did not significantly affect the volatile development. Ripening time, and color development were measured daily while disease incidence and severity, weight loss, firmness, and concentrations of soluble solids, titratable acidity, ascorbic acid, total carotenoids, and volatiles were determined at the eating soft ripe stage. Hot water dipping or fungicide treatments (at ambient or at a high temperature) reduced postharvest diseases incidence and severity. Fruit quality (soluble solids concentration, titratable acidity, ascorbic acid and total caretonoids) was not substantially affected by any of the treatments.

Edible coatings influence fruit ripening, quality, and aroma biosynthesis in mango fruit.

The effects of different edible coatings on mango fruit ripening and ripe fruit quality parameters including color, firmness, soluble solids concentrations, total acidity, ascorbic acid, total carotenoids, fatty acids, and aroma volatiles were investigated. Hard mature green mango (Mangifera indica L. cv. Kensigton Pride) fruits were coated with aqueous mango carnauba (1:1 v/v), Semperfresh (0.6%), Aloe vera gel (1:1, v/v), or A. vera gel (100%). Untreated fruit served as the control. Following the coating, fruits were allowed to dry at room temperature and packed in soft-board trays to ripen at 21+/-1 degrees C and 55.2+/-11.1% relative humidity until the eating soft stage. Mango carnauba was effective in retarding fruit ripening, retaining fruit firmness, and improving fruit quality attributes including levels of fatty acids and aroma volatiles. Semperfresh and A. vera gel (1:1 or 100%) slightly delayed fruit ripening but reduced fruit aroma volatile development. A. vera gel coating did not exceed the commercial mango carnauba and Semperfresh in retarding fruit ripening and improving aroma volatile biosynthesis.

Red clover Trifolium pratense L. phytoestrogens: UV-B radiation increases isoflavone yield, and postharvest drying methods change the glucoside conjugate profiles.

Isoflavone extracts of red clover Trifolium pratense L. (cv. Pawera) with dissimilar glucoside conjugate profiles were obtained by employing different postharvest drying methods. The most prominent isoflavones found were formononetin and biochanin A and their corresponding glucosides and malonyl glucoside esters. Postharvest freeze drying inhibited the conversion of the glycosides to the aglycones, while vacuum drying allowed for maximum conversion of the glycosides to their corresponding aglycones. Air drying produced a low level of the aglycones formononetin and biochanin A, and oven drying promoted decarboxylation of the malonyl glucosides to the acetyl glucosides. Exposure to enhanced UV-B radiation resulted in an increase in total formononetin and biochanin A isoflavone levels, indicating that harvest during a period of high ambient UV-B radiation may be appropriate for maximum yield. The levels of caffeic acid and flavonols also increased by about 40 and 250%, respectively, on exposure to enhanced UV-B radiation.

The fluorescence and photostabilities of naturally occurring isoflavones.

The 5,7-dihydroxyisoflavones do not emit detectable fluorescence and are significantly more photostable than the two 7-hydroxy-5-deoxyisoflavones, daidzein and formononetin. The latter isoflavones emit fluorescence that depends on the basicity of the solution and the polarity of the solvent. Comparison of the spectral distributions of the emission in methanol in the presence and absence of base indicates that it originates from the conjugate anion excited singlet states. The fluorescence of daidzein and formononetin exhibit large Stokes shifts to longer wavelengths in methanol, ethanol, hexanol and acetonitrile and the magnitudes of these shifts increase with solvent polarity. This indicates that the emission originates from excited singlet states with much larger dipole moments than those of the corresponding ground states. Values of 8.3 D and 6.5 D were determined for daidzein and formononetin respectively. The photostabilities of formononetin and daidzein both increase with increasing solvent polarity and in corresponding solvents, the photostability of daidzein is higher than that of formononetin, behaviour which is attributed to the greater antioxidant activity of daidzein.

Flavonoid gene expression and UV photoprotection in transgenic and mutant Petunia leaves.

The effects of UVB radiation on plant growth rate, gene expression and flavonoid content in wild-type, and in transgenic and mutant F3'H deficient Petunia lines have been studied for the first time. In wild-type Petunia, UVB induced an increase in total levels of flavonols and this was due to an up-regulation of several genes in the phenylpropanoid pathway. Furthermore, UVB induced a higher rate of production of dihydroxylated flavonols than mono-hydroxylated equivalents. Thus, the ratio of quercetin (ortho-dihydroxylated) to kaempferol (monohydroxylated) increased. In the F3H deficient mutant line, increasing UVB resulted in up-regulation of all of the basic flavonoid biosynthetic genes. Total flavonoids increased to levels significantly higher than in control plants, and the predominant flavonoid was kaempferol. The leaves of these plants grew at a significantly slower rate than comparably treated wild-type plants under ambient or enhanced UVB radiation. This suggests that the predominance of quercetin in the wild-type confers a protective advantage that is not matched in the mutant, even with higher overall flavonoid levels. In contrast, the antisense F3H construct produced an unexpected down-regulation of C4H, CHS and CHI transcription. This resulted in lower total flavonoid production in these plants. The growth rate of these plants was not impaired in UVB to a statistically significant extent, and the Q:K ratio did not change with increasing UVB radiation. This investigation has established a likely correlation between the effect of UVB on plant growth rate, the level of activity of the F3'H gene, and the proposed photoprotection afforded by an increased Q:K ratio.