Implications of dietary phenolic compounds for human health and disease prevention have been indicated by a body of literature. A greenhouse pot study was performed to investigate the impacts of fertilizer source and preventive insecticide application on phenolic compound levels in pac choi [Brassica rapa (L.) cv. Mei Qing]. A two-way randomized complete-block design with five replications was used in this experiment. Fertilizer source consisted of two levels: conventional fertilizer (pre-plant application of Osmocote slow-release fertilizer), and organic fertilizer (pre-plant application of vermicompost and fertigation with compost tea and fish emulsion). Insecticide application consisted of three levels: organic (pyrethrin) vs. conventional (permethrin), and a plain water control. At harvest, total phenolics and individual phenolic compounds in pac choi leaves (blades) were analyzed by Folin assay and HPLC, respectively. Head weight of pac choi was significantly higher under conventional fertilizer treatment, while it was not affected by insecticides. Total phenolic content of pac choi was significantly increased by organic fertilizer treatment. HPLC results indicated that organic fertilizer treatment resulted in significantly higher levels of individual phenolic compounds, including chlorogenic acid and ferulic acid. In contrast, preventive insecticide application showed little effect on the phenolics in pac choi. Correlation analysis excluded the influence of plant size (head weight) on phenolic content in pac choi. Differential N-forms, rates of nutrient release, and/or variable nutrient content in organic and conventional fertilizer treatments may contribute to elevated phenolic content in organically fertilized pac choi.
Xin Zhao, Edward Carey, James Nechols, Kim Williams, and Weiqun Wang
Jingtair Siriphanich and Adel A. Kader
An atmosphere of air + 15% CO2 caused CO2 injury in lettuce (Lactuca sativa L.) in about 10 days at 0°C. However, subsequent removal of CO2 was necessary for the brown stain symptoms to develop. Under CO2 treatment, phenylalanine ammonia lyase (PAL) was induced and its activity correlated well with the development of the injury. Nevertheless, PAL activity did not seem responsible for the differences in susceptibility to CO2 injury among the 3 lettuce cultivars included in this study. Prevention of the development of brown stain symptoms by CO2 probably was due to its inhibition of phenolics production and the inhibition of polyphenol oxidase activity.
M. B. Isman and S. S. Duffey
Semi-purifled extracts of phenolics from foliage of tomato (Lycopersicon esculentum Mill.) inhibit larval growth of the fruitworm, Heliothis zea (Boddie), when added to artificial diets for this insect pest. The degree of inhibition of growth (dose-response) is directly related to the quantity of total phenolics in extracts added to diets, whether the extracts are of equivalent amounts of foliage from different cultivars or of foliage pooled from several cultivars added in serial dilution. Dose-responses for extracts were equal to those obtained with pure chlorogenic acid or rutin, major phenolic constituents of tomato foliage. Also, equivalent quantities of phenolics from 5 different cultivars inhibited larval growth equally when added to diets. These 3 sets of observations show that isolated tomato foliar phenolics affect H. zea larvae quantitatively, with no measurable qualitative differences between cultivars. When 2nd instar larvae were reared on excised leaflets from several cultivars of field-grown tomatoes, significant differences in larval growth between cultivars were obtained, which were consistent through two years. However, significant relationships between foliar phenolic content and larval growth were not obtained, partially because of the highly variable nature of phenolic content within and between plants. Our results suggest that phenolics in tomato foliage at the minimum contribute a substantial background level of antibiosis to H. zea.
Jenny Heringer Vires, Robert Geneve, and Robert Anderson
Purple coneflower, Echinacea sp. (Asteraceae), is a herbaceous perennial native to North America. Within the past decade, extensive research has been conducted to confirm echinacea's immunostimulatory, antiviral, and antibacterial benefits to humans. E. angustifolia, E. purpurea, and E. pallida are the primary species grown and studied for the herbal industry. However, there are other species and cultivars that may produce higher yields in biomass and chemical quality. The objective for this study is to evaluate the differences in biomass and phenolic content of five cultivars of E. purpurea and five species of Echinacea under Kentucky growing conditions. Differences in biomass (dry weight) of Echinacea species and cultivars harvested after the first year of growth was determined. There was a significant difference in total dry weight between E. purpurea cultivars. E. purpurea `Bright Star' and `Clio' produced significantly greater total dry weight compared to all other cultivars. There was no significant difference in root or flower biomass between cultivars. Biomass production differed between Echinacea species for root, vegetative, and flower parts. The total biomass of E. purpurea and E. tennesseensis was significantly higher compared to other species. E. pallida and E. paradoxa were not significantly different from E. purpurea in root biomass, even though both species produced less above-ground growth. E. tennesseensis produced 45% to 105% more flowers compared to other species. Differences in phenolic content between species and cultivars will also be presented.
Yuan Yongbing, A. M. Simeone, and P. Cappelini
Peach rootstocks Rancho Resistant (RR) and GF 677 are resistant and susceptible to nematodes, respectively. One-year-old seedlings of RR, GF677 and their reciprocal grafts were inoculated with 10,000 larvae. Both inoculated and control plants were harvested at intervals for assay. Phenylalanine ammonia lyase (PAL) activity and soluble phenol content were enhanced in both RR and GF677 after inoculation, but RR always had a 2-fold higher peroxidase (PO) activity than GF677. When GF677 was grafted on RR, the resistance of RR was not altered. When RR was grafted onto GF677, the number of galls on the plant were 66% and 77% less than on GF677 2 weeks and 2 months after inoculation, respectively. However, no interaction was found in the reciprocal graft. The results showed that higher soluble phenol content and PAL activity induced by nematode attack were common features of RR and GF677, and a positive relation between PO activity and resistance to nematode existed in the two rootstocks.
Sylvia M. Blankenship and Daryl G. Richardson
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.
D.R. Rudell, J.P. Mattheis, X. Fan, and J.K. Fellman
Effects of artificial ultraviolet-visible light and methyl jasmonate (MJ) treatment on `Fuji' apple [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.] fruit peel anthocyanin, phenolic, carotenoid, and chlorophyll production were examined using tristimulus color analysis and reverse-phase high performance liquid chromatography. Anthocyanin synthesis was enhanced by light and MJ treatment. Chlorogenic acid and most cyanidin, quercetin, and phloretin glycosides increased with MJ treatment concentration. Light alone also promoted increased production of most of these compounds. Production of catechin, (-)epicatechin, quercetin, and quercetrin was not enhanced by either light or MJ treatment. Light and MJ enhanced ß-carotene and chlorophyll b, synthesis but not xanthophyll or chlorophyll a synthesis. The chlorophyll a/b ratio decreased with MJ dosage. Results suggest MJ may provide a viable means of enhancing apple fruit coloration and other photoprotective mechanisms. Chemical name used: methyl 3-oxo-2-(2-pentenyl)cyclopentane-1-acetate (methyl jasmonate).
Jungmin Lee, Chad E. Finn, and Ronald E. Wrolstad
The total anthocyanin and total phenolic content of wild (samples from 4 populations) and cultivated (samples from 32 populations) Pacific Northwestern American Vaccinium species (V. membranaceum, V. ovalifolium, and V. deliciosum) were evaluated. The total monomeric anthocyanin content of all huckleberry samples analyzed ranged from 101 to 400 mg/100 g (expressed as cyanidin-3-glucoside), and the total phenolics varied from 367 to 1286 mg/100 g (expressed as gallic acid). Cluster analysis separated the samples into four different groups based on their anthocyanin and total phenolic content. Two groups had greater anthocyanin pigment and total phenolics; one consisted entirely of cultivated V. ovalifolium (LIG10, VAC485, VAC487, LIG33, LIG9, LIG2, and VAC349) and the other consisted of just cultivated V. membranaceum (LIG25). Significant variations in total anthocyanins, total phenolics, and the ratio of the total anthocyanins and total phenolics were observed among the different V. membranaceum, V. ovalifolium, and V. deliciosum populations cultivated in the Willamette Valley, Ore. The profile of the individual anthocyanins of the wild V. membranaceum, wild V. ovalifolium, and V. corymbosum `Rubel' were conducted by high-performance liquid chromatography. The chromatograms of V. membranaceum, V. ovalifolium, and `Rubel' were distinctly different in the amounts of delphinidin, cyanidin, and malvidin glycosides.
Zhiguo Ju and William J. Bramlage
Phenolics were extracted from fruit cuticles of `Delicious', `Golden Delicious', `Empire', and `Cortland' apples, using either cuticular wax scraped from fruit peel or enzyme-isolated cuticles. The concentrations of free phenolics in fruit cuticle ranged from 8 to 45 mg•g-1, and bound phenolics ranged from 50 to 110 mg•g-1 in these cultivars. Free cuticular phenolic concentrations in the four cultivars were in the order `Golden Delicious' > `Delicious' > `Empire' > `Cortland'. In a linoleate emulsion (oil-in-water) system, diphenylamine (DPA, lipophilic) displayed higher antioxidant activity than methanol-extracted cuticular phenolics (hydrophilic). In an α-farnesene-hexane (bulk oil) system, however, antioxidant activities of methanol-extracted cuticular phenolics were higher than that of DPA. Lipid-soluble antioxidants (LSAs) from cuticle displayed higher activity in the linoleate emulsion system than in α-farnesene-hexane system. Only about 10% to 15% of the total LSA activity in fruit peel was detected in isolated fruit cuticle. Among the four cultivars, LSA activity in epidermal and hypodermal cells was similar in `Golden Delicious', `Empire', and `Cortland' apples, while `Delicious' had lower activity.
James D. Spiers, Fred T. Davies, Scott A. Finlayson, Chuanjiu He, Kevin M. Heinz, and Terri W. Starman
This research focused on the effects of nitrogen fertilization on jasmonic acid accumulation and total phenolic concentrations in gerbera. The phytohormone jasmonic acid is known to regulate many plant responses, including inducible defenses against insect herbivory. Phenolics are constitutive secondary metabolites that have been shown to negatively affect insect feeding. Gerbera jamesonii `Festival Salmon Rose' plants were grown in a growth chamber and subjected to either low fertilization (only supplied with initial fertilizer charge present in professional growing media) or high fertilization (recommended rate = 200 mg·L-1 N). Plants were fertilized with 200 mL of a 15N–7P–14K fertilizer at 0 or 200 mg·L-1 N at each watering (as needed). Treatments consisted of ±mechanical wounding with a hemostat to one physiologically mature leaf and the subsequent harvest of that leaf at specified time intervals for jasmonic acid quantification. Total phenolics were measured in physiologically mature and young leaves harvested 0 and 10 hours after ±mechanical wounding. Low-fertility plants had reduced aboveground dry mass, were deficient in nitrogen and phosphorus, and had about a 10× higher concentration of total phenolics when compared to high fertility plants. In low-fertility plants, young leaves had greater concentrations of phenolics compared to physiologically mature leaves. There were no differences in total phenolics due to wounding. The effect of nitrogen fertilization on jasmonic acid accumulation will also be discussed.