Chilling-induced changes in the antioxidant status of basil plants

Six cultivars of basil, ‘Genovese’, ‘Purpurascens’, ‘Cinnamon’, ‘Crispum’, ‘Citriodora’, and ‘Siam Queen’, at the age of 8 weeks, were subjected to low temperature (6 °C for 8 days) or 18 °C (control). Content of hydrogen peroxide (H₂O₂), malondialdehyde (MDA), total phenolics, and l-ascorbic acid were assessed in basil leaves after low temperature exposure. Activity of peroxidase (POD), and catalase (CAT) enzymes and 2,2-diphenyl-1-picrylhydrazyl (DPPH^·) radical scavenging activity were also determined. The greatest increase in H₂O₂ was observed for lettuce leaf basil, by 104 % in comparison to the control, while most noticeable increase in the content of MDA was noted for lemon basil (by 77 %). Chilling treatment resulted in higher POD activity in two cultivars: Thai and green basil, changes in CAT activity was negligible for almost all tested genotypes, with an exception of Thai basil, for which activity of this enzyme dropped. Chilling induced the increase of l-ascorbic acid in most tested basil cultivars, but total phenolic content increased significantly only in lettuce leaf basil. Higher ability in scavenging free radicals was shown in basil treated with 6 °C, especially the red basil cultivar. For this genotype, DPPH^· radical scavenging activity was the highest among tested cultivars and was parallel to the highest content of phenolics. The results indicated overproduction of H₂O₂, deterioration of membrane integrity, and activation of enzymatic and/or non-enzymatic defence mechanisms in basil with an evidence of genotypic variation as the response to low temperature.     

Highly sensitive and specific PCR assay for reliable detection of Cyclospora cayetanensis oocysts

Multiple outbreaks of food-borne gastroenteritis caused by the coccidian parasite Cyclospora cayetanensis have been reported annually in North America since 1995. Detection of C. cayetanensis contamination typically relies on laborious and subjective microscopic examination of produce washes. Molecular detection methods based on nested PCR, restriction fragment length polymorphism, or multiplex PCR have been developed for C. cayetanensis; however, they have not been adequately validated for use on food products. Further challenges include reliably extracting DNA from coccidian oocysts since their tough outer wall is resistant to lysis and overcoming PCR inhibitors in sample matrices. We describe preliminary validation of a reliable DNA extraction method for C. cayetanensis oocysts and a sensitive and specific novel PCR assay. The sensitivity and repeatability of the developed methods were evaluated by multiple DNA extractions and PCR amplifications using 1,000-, 100-, 10-, or 1-ooycst aliquots of C. cayetanensis oocysts in water or basil wash sediment. Successful PCR amplification was achieved on 15 and 5 replicates extracted from aliquots containing 1,000 oocysts in water and basil wash, respectively. All 45 replicates of the 100-oocyst aliquots in water and 5 in basil wash were amplified successfully, as were 43/45 and 41/45 of the 10- and 1-oocyst aliquots in water and 9/15 and 2/15 in basil wash, respectively. The developed primers showed no cross-reactivity when tested against bacteria, nematodes, and protozoans, including Eimeria, Giardia, and Cryptosporidium. Our results indicate that these methods are specific, can reliably detect a single oocyst, and overcome many of the limitations of microscopic diagnosis.     

Evaluation of a Loop-Mediated Isothermal Amplification Suite for the Rapid,Reliable, and Robust Detection of Shiga Toxin-Producing Escherichia coli in Produce

Shiga toxin-producing Escherichia coli (STEC) strains are a leading cause of produce-associated outbreaks in the United States. Rapid, reliable, and robust detection methods are needed to better ensure produce safety. We recently developed a loop-mediated isothermal amplification (LAMP) suite for STEC detection. In this study, the STEC LAMP suite was comprehensively evaluated against real-time quantitative PCR (qPCR) using a large panel of bacterial strains (n = 156) and various produce items (several varieties of lettuce, spinach, and sprouts). To simulate real-world contamination events, produce samples were surface inoculated with a low level (1.2 to 1.8 CFU/25 g) of individual STEC strains belonging to seven serogroups (O26, O45, O103, O111, O121, O145, and O157) and held at 4°C for 48 h before testing. Six DNA extraction methods were also compared using produce enrichment broths. All STEC targets and their subtypes were accurately detected by the LAMP suite. The detection limits were 1 to 20 cells per reaction in pure culture and 10⁵ to 10⁶ CFU per 25 g (i.e., 10³ to 10⁴ CFU per g) in produce, except for strains harboring the stx_2c, eae-β, and eae-θ subtypes. After 6 to 8 h of enrichment, the LAMP suite achieved accurate detection of low levels of STEC strains of various stx₂ and eae subtypes in lettuce and spinach varieties but not in sprouts. A similar trend of detection was observed for qPCR. The PrepMan Ultra sample preparation reagent yielded the best results among the six DNA extraction methods. This research provided a rapid, reliable, and robust method for detecting STEC in produce during routine sampling and testing. The challenge with sprouts detection by both LAMP and qPCR calls for special attention to further analysis.     

The effect of essential oils of basil on the growth of Aeromonas hydrophila and Pseudomonas fluorescens

Basil essential oils, including basil sweet linalool (BSL) and basil methyl chavicol (BMC), were screened for antimicrobial activity against a range of Gram-positive and Gram-negative bacteria, yeasts and moulds using an agar well diffusion method. Both essential oils showed antimicrobial activity against most of the micro-organisms examined except Clostridium sporogenes , Flavimonas oryzihabitans , and three species of Pseudomonas . The minimum inhibitory concentration (MIC) of BMC against Aeromonas hydrophila and Pseudomonas fluorescens in TSYE broth (as determined using an indirect impedance method) was 0·125 and 2% (v/v), respectively; the former was not greatly affected by the increase of challenge inoculum from 10³ to 10⁶ cfu ml⁻¹. Results with resting cells demonstrated that BMC was bactericidal to both Aer. hydrophila and Ps. fluorescens . The growth of Aer. hydrophila in filter-sterilized lettuce extract was completely inhibited by 0·1% (v/v) BMC whereas that of Ps. fluorescens was not significantly affected by 1% (v/v) BMC. In addition, the effectiveness of washing fresh lettuce with 0·1 or 1% (v/v) BMC on survival of natural microbial flora was comparable with that effected by 125 ppm chlorine.     

Systemic spread of downy mildew in basil plants and detection of the pathogen in seed and plant samples

Downy mildew on sweet basil (Ocimum basilicum L.) occurs worldwide. Contaminated seeds are considered as the primary inoculum source. So far no strategy to control the disease is available. Hence, the use of pathogen-free seeds is the only alternative to prevent disease outbreaks. Therefore, a rapid diagnostic method for seed testing is urgently needed. The sensitivity of a specific PCR method for direct detection of the downy mildew pathogen Peronospora belbahrii on basil samples, particularly on seeds, was evaluated. The applied PCR method proved to be very sensitive for direct detection of the pathogen on seeds and plant samples. The PCR detection limit of P. belbahrii in artificially infested seeds corresponded to the DNA amount of a single spore per seed. Additionally, the systemic spread of the pathogen from naturally infected seeds was investigated. The experiments showed that outgrowing basil plants were latently infected with the downy mildew pathogen, and the infection continued within the plant. Contaminated seeds were harvested from symptomless latently infected plants. These results support the implementation of PCR-based detection in a seed certification scheme and the necessity to control the pathogen on seeds. The PCR method can also be used for evaluation of pathogen control on seeds based on detection of the pathogen in outgrowing plants.     

Optimizing edible fungal growth and biodegradation of inedible crop residues using various cropping methods

Long-term manned space flights to Mars require the development of an advanced life support (ALS) ecosystem including efficient food crop production, processing and recycling waste products thereof. Using edible white rot fungi (EWRF) to achieve effective biomass transformation in ALS requires optimal and rapid biodegradative activity on lignocellulosic wastes. We investigated the mycelial growth of Lentinula edodes and Pleurotus ostreatus on processed residues of various crops under various cropping patterns. In single cropping, mycelial growth and fruiting in all strains were significantly repressed on sweet potato and basil. However, growth of the strains was improved when sweet potato and basil residues were paired with rice or wheat straw. Oyster mushroom (Pleurotus) strains were better than shiitake (L. edodes) strains under single, paired, and mixed cropping patterns. Mixed cropping further eliminated the inherent inhibitory effect of sweet potato, basil, or lettuce on fungal growth. Co-cropping fungal species had a synergistic effect on rate of fungal growth, substrate colonization, and fruiting. Use of efficient cropping methods may enhance fungal growth, fruiting, biodegradation of crop residues, and efficiency of biomass recycling.     

Cyclooxygenase inhibitory and antioxidant cyanidin glycosides in cherries and berries

Anthocyanins from tart cherries, Prunus cerasus L. (Rosaceae) cv. Balaton and Montmorency; sweet cherries, Prunus avium L. (Rosaceae); bilberries, Vaccinum myrtillus L. (Ericaceae); blackberries, Rubus sp. (Rosaceae); blueberries var. Jersey, Vaccinium corymbosum L. (Ericaceae); cranberries var. Early Black, Vaccinium macrocarpon Ait. (Ericaceae); elderberries, Sambucus canadensis (Caprifoliaceae); raspberries, Rubus idaeus (Rosaceae); and strawberries var. Honeoye, Fragaria x ananassa Duch. (Rosaceae), were investigated for cyclooxygenase inhibitory and antioxidant activities. The presence and levels of cyanidin-3-glucosylrutinoside 1 and cyanidin-3-rutinoside 2 were determined in the fruits using HPLC. The antioxidant activity of anthocyanins from cherries was comparable to the commercial antioxidants, tert-butylhydroquinone, butylated hydroxytoluene and butylated hydroxyanisole, and superior to vitamin E, at a test concentration of 125 microg/ml. Anthocyanins from raspberries and sweet cherries demonstrated 45% and 47% cyclooxygenase-I and cyclooxygenase-II inhibitory activities, respectively, when assayed at 125 microg/ml. The cyclooxygenase inhibitory activities of anthocyanins from these fruits were comparable to those of ibuprofen and naproxen at 10 microM concentrations. Anthocyanins 1 and 2 are present in both cherries and raspberry. The yields of pure anthocyanins 1 and 2 in 100 g Balaton and Montmorency tart cherries, sweet cherries and raspberries were 21, 16.5; 11, 5; 4.95, 21; and 4.65, 13.5 mg, respectively. Fresh blackberries and strawberries contained only anthocyanin 2 in yields of 24 and 22.5 mg/100 g, respectively. Anthocyanins 1 and 2 were not found in bilberries, blueberries, cranberries or elderberries.     

Binding of virus-like particles of Norwalk virus to romaine lettuce veins

Noroviruses (NoV) annually cause millions of cases of gastrointestinal disease in the United States. NoV are associated with raw shellfish outbreaks, particularly oysters, which are thought to bioaccumulate NoV particles during the filter-feeding process. NoV outbreaks, however, have also been known to occur from other common-source food-borne vehicles, such as lettuce, frozen raspberries, and salad. In this study, we evaluated romaine lettuce as a potential vehicle for NoV transmission by testing the binding and distribution of NoV to the surface of romaine. Recombinant Norwalk virus-like particles (rNVLP) applied to the surface of romaine lettuce localized as large clusters primarily on the leaf veins. An extract of romaine lettuce leaves in phosphate-buffered saline (PBS) (romaine extract [RE]) bound rNVLP in a dose-dependent manner. RE did not bind rNVLP by histo-blood group antigens (HBGA), nor was RE competitive with rNVLP binding to porcine gastric mucin. These results suggested that non-HBGA molecules in RE bind rNVLP by a binding site(s) that is different from the defined binding pocket on the virion. Extracts of cilantro, iceberg lettuce, spinach, and celery also bound rNVLP. Samples of each of the vegetables spiked with rNVLP and tested with anti-NVLP antibody revealed by confocal microscopy the presence of rNVLP not only on the veins of cilantro but also throughout the surface of iceberg lettuce.     

Rapid polymerase chain reaction method for detection of Vibrio cholerae in foods.

The polymerase chain reaction was used to selectively amplify sequences within the cholera toxin operon from Vibrio cholerae O1. Oysters, crabmeat, shrimp, and lettuce were seeded with V. cholerae and then homogenized or washed with alkaline peptone water, followed by short-term (6- to 8-h) enrichment. A detection limit of as few as 1 V. cholerae CFU per 10 g of food was obtained with amplification reactions from crude bacterial lysates. The method is extremely rapid and obviates the need for DNA isolation from a variety of complex food matrices.     

The cytotoxic targets of anatase or rutile + anatase nanoparticles depend on the plant species

The potential toxicity of nanoparticles (NPs) is under debate. Information about TiO₂ NPs phytotoxicity is still limited partly due to the different TiO₂ NP forms that may be found in the environment. The present work investigated the impact of different TiO₂ NPs forms (rutile and anatase) on germination, growth, cell cycle profile, ploidy level, and micronucleus formation in Lactuca sativa (lettuce) and Ocimum basilicum (basil). Seeds were exposed to anatase (ana) or rutile + anatase (rut+ana) at concentrations 5 - 150 mg dm^-3 for 5 d and after that different parameters were analyzed. Rut+ana showed high potential to impair germination and growth. On the other hand, ana alone showed a positive influence on seedling growth. Despite that, ana induced severe alterations in cell cycle dynamics. Regarding species, basil was more sensitive to TiO₂ NPs cytostatic effects (delay/arrest in G₀/G₁ phase), whereas in lettuce, TiO₂ NPs were more genotoxic (micronucleus formation increase). Finally, we propose that, besides germination and plant growth, cell cycle dynamics and micronucleus formation can be sensitive biomarkers of these NPs.     

Selection,Characterization and Application of Nucleic Acid Aptamers for the Capture and Detection of Human Norovirus Strains

Human noroviruses (HuNoV) are the leading cause of acute viral gastroenteritis and an important cause of foodborne disease. Despite their public health significance, routine detection of HuNoV in community settings, or food and environmental samples, is limited, and there is a need to develop alternative HuNoV diagnostic reagents to complement existing ones. The purpose of this study was to select and characterize single-stranded (ss)DNA aptamers with binding affinity to HuNoV. The utility of these aptamers was demonstrated in their use for capture and detection of HuNoV in outbreak-derived fecal samples and a representative food matrix. SELEX (Systematic Evolution of Ligands by EXponential enrichment) was used to isolate ssDNA aptamer sequences with broad reactivity to the prototype GII.2 HuNoV strain, Snow Mountain Virus (SMV). Four aptamer candidates (designated 19, 21, 25 and 26) were identified and screened for binding affinity to 14 different virus-like particles (VLPs) corresponding to various GI and GII HuNoV strains using an Enzyme-Linked Aptamer Sorbant Assay (ELASA). Collectively, aptamers 21 and 25 showed affinity to 13 of the 14 VLPs tested, with strongest binding to GII.2 (SMV) and GII.4 VLPs. Aptamer 25 was chosen for further study. Its binding affinity to SMV-VLPs was equivalent to that of a commercial antibody within a range of 1 to 5 µg/ml. Aptamer 25 also showed binding to representative HuNoV strains present in stool specimens obtained from naturally infected individuals. Lastly, an aptamer magnetic capture (AMC) method using aptamer 25 coupled with RT-qPCR was developed for recovery and detection of HuNoV in artificially contaminated lettuce. The capture efficiency of the AMC was 2.5–36% with an assay detection limit of 10 RNA copies per lettuce sample. These ssDNA aptamer candidates show promise as broadly reactive reagents for use in HuNoV capture and detection assays in various sample types.     

Effects of high pressure processing on Toxoplasma gondii oocysts on raspberries

Oocysts are the environmentally resistant life stage of Toxoplasma gondii. Humans can become infected by accidentally ingesting the oocysts in water or from contaminated produce. Severe disease can occur in immunocompromised individuals, and nonimmune pregnant women can infect their offspring. Chronic infection is associated with decreased mental functions, vision and hearing problems, and some mental disorders such as schizophrenia. High pressure processing (HPP) is a commercial method used to treat food to eliminate pathogens. Treatment of produce to eliminate viable T. gondii oocysts would provide a means to protect consumers. The present study was done to better define the effects of HPP on oocysts placed on raspberries. Raspberries were chosen because they are a known source of a related human intestinal parasite, Cyclospora cayetanensis. Raspberries were inoculated with 5 x 10(4) oocysts of the VEG strain of T. gondii for 20 hr prior to HPP. Individual raspberries were exposed to 500 MPa, 400 MPa, 340 MPa, 300 MPa, 270 MPa, 250 MPa, 200 MPA, 100 MPa, or no MPa treatment for 60 sec in a commercial HPP unit (1 MPa = 10 atm = 147 psi). Treatment of raspberries with 340 MPa for 60 sec was needed to render oocysts spot inoculated on the raspberries noninfectious for mice. Treatment of raspberries with 200 MPa or less for 60 sec was not effective in rendering oocysts noninfectious for mice.     

Agronomic aspects of strip intercropping lettuce with alyssum for biological control of aphids

Organic lettuce growers in California typically use insectary strips of alyssum (Lobularia maritima (L.) Desv.) to attract hoverflies (Syrphidae) that provide biological control of aphids. A two year study with transplanted organic romaine lettuce in Salinas, California investigated agronomic aspects of lettuce monoculture and lettuce-alyssum strip intercropping on beds in replacement intercropping treatments where alyssum transplants replaced 2 to 8% of the lettuce transplants, and in additive intercropping treatments where alyssum transplants were added to the standard lettuce density without displacing lettuce transplants. Alyssum and lettuce dry matter (DM) were determined at lettuce maturity. Alyssum transplants produced less shoot DM in the additive than in the replacement intercropping treatments. The number of open inflorescences of alyssum increased with alyssum DM, and among treatments ranged from 2 to15 inflorescences per lettuce head. Compared with monoculture lettuce, lettuce heads on intercropped beds were slightly smaller and had lower nitrogen concentrations in the both additive treatments and in some replacement treatments. This research provides the first information on a novel additive intercropping approach to provide alyssum floral resources for biological control of lettuce aphids, and suggests that this approach may be a more land-efficient particularly for producing smaller lettuce heads for romaine hearts or for markets with less strict size requirements. Additional research is needed to determine if the increased competition between alyssum and lettuce in additive intercropping would reduce lettuce yields for wholesale markets with larger head size requirements. Practical aspects of implementing the various intercropping arrangements and alternatives are discussed.     

Rearing of Lymnaea columella (Say, 1817), intermediate host of Fasciola hepatica (Linnaeus, 1758)

The intermediate host of Fasciola hepatica, Lymnaea columella, collected in Belo Horizonte, Minas Gerais, Brazil, was reared in our laboratory. The aim of the current study was to standardize a rearing and maintenance technique. Two kinds of diet were tested: fresh lettuce (A) and rodent ration + 10% CaCO3 plus fresh lettuce (B). The age for the beginning of oviposition ranged from 27 to 57 days. Ten days after oviposition at 24.7 degrees C, 100% eclosion occurred. The complete life cycle varied from 37 to 67 days. The average numbers of eggs per egg mass were 26.3 and 31.1 with diets (A) and (B), respectively. The lettuce and ration fed snails presented a increased growth although the difference was not statistically significant (p > 0.05). The mortality rate varied from 40 to 64% after 90 days. The maximum longevity was 183 days, 21.5 mm length and 11 mm wide. The methodology to mass breed and maintain these snails was found to be suitable in the laboratory     

Quantifying the reduction in potential health risks by determining the sensitivity of poliovirus type 1 chat strain and rotavirus SA-11 to electron beam irradiation of iceberg lettuce and spinach

Fresh produce, such as lettuce and spinach, serves as a route of food-borne illnesses. The U.S. FDA has approved the use of ionizing irradiation up to 4 kGy as a pathogen kill step for fresh-cut lettuce and spinach. The focus of this study was to determine the inactivation of poliovirus and rotavirus on lettuce and spinach when exposed to various doses of high-energy electron beam (E-beam) irradiation and to calculate the theoretical reduction in infection risks that can be achieved under different contamination scenarios and E-beam dose applications. The D(10) value (dose required to reduce virus titers by 90%) (standard error) of rotavirus on spinach and lettuce was 1.29 (± 0.64) kGy and 1.03 (± 0.05) kGy, respectively. The D(10) value (standard error) of poliovirus on spinach and lettuce was 2.35 (± 0.20) kGy and 2.32 (± 0.08) kGy, respectively. Risk assessment of data showed that if a serving (～14 g) of lettuce was contaminated with 10 PFU/g of poliovirus, E-beam irradiation at 3 kGy will reduce the risk of infection from >2 in 10 persons to approximately 6 in 100 persons. Similarly, if a serving size (～0.8 g) of spinach is contaminated with 10 PFU/g of rotavirus, E-beam irradiation at 3 kGy will reduce infection risks from >3 in 10 persons to approximately 5 in 100 persons. The results highlight the value of employing E-beam irradiation to reduce public health risks but also the critical importance of adhering to good agricultural practices that limit enteric virus contamination at the farm and in packing houses.     

Ethanol production from candidate energy crops: water hyacinth (Eichhornia crassipes) and water lettuce (Pistia stratiotes L.)

Fermentation modes and microorganisms related to two typical free-floating aquatic plants, water hyacinth and water lettuce, were investigated for their use in ethanol production. Except for arabinose, sugar contents in water lettuce resembled those in water hyacinth leaves. Water lettuce had slightly higher starch contents and lower contents of cellulose and hemicellulose. A traditional strain, Saccharomyces cerevisiae NBRC 2346, produced 14.4 and 14.9 g l(-1) ethanol, respectively, from water hyacinth and water lettuce. Moreover, a recombinant strain, Escherichia coli KO11, produced 16.9 and 16.2 g l(-1) ethanol in the simultaneous saccharification and fermentation mode (SSF), which was more effective than the separated hydrolysis and fermentation mode (SHF). The ethanol yield per unit biomass was comparable to those reported for other agricultural biomasses: 0.14-0.17 g g-dry(-1) for water hyacinth and 0.15-0.16 g g-dry(-1) for water lettuce.     

Note: Occurrence and persistence of culturable clostridial spores on the leaves of horticultural plants

Clostridial spores were found in numbers from less than 1 to over 50 colony-forming units cm^-2 on mature leaves of 19 species of horticultural plants under commercial cultivation in five localities in Apulia (SE Italy). Of 1828 clostridial isolates, 87% were identified phenotypically and ascribed to Clostridium pasteurianum, Cl. sporogenes, Cl. butyricum, Cl. roseum, Cl. perfringens, Cl. felsineum and Cl. acetobutylicum , in decreasing order of frequency. When spore suspensions of Cl. pasteurianum, Cl. perfringens, Cl. roseum and Cl. sporogenes were inoculated onto the leaves of basil, leaf-beet, lettuce, rocket-salad, spinach and tomato in the greenhouse, spore counts at first invariably declined shortly after inoculation, then rose again significantly for Cl. pasteurianum and Cl. perfringens on basil and for Cl. sporogenes on tomato in summer.     

Impact of light-emitting diode irradiation on photosynthesis,phytochemical composition and mineral element content of lettuce cv. Grizzly

Light-emitting diodes (LEDs) are a promising technology with a potential to improve the irradiance efficiency, light quality, and the light spectrum for increasing plant yield and quality. In this experiment, we investigated the impacts of various LED light qualities, including 100% red, 100% blue, 70% red + 30% blue, and 100% white, on the growth and photosynthesis, phytochemical contents, and mineral element concentrations in lettuce (Lactuca sativa L. cv. ‘Grizzly’) in comparison to normal greenhouse conditions. Photon flux of 300 µmol m^?2 s^?1 was provided for 14 h by 120 LEDs set on a 60 cm × 60 cm sheet of aluminum platform in the growth chambers, where plants were grown for 60 d. Fresh mass per plant was significantly higher when grown under 100% blue and 70% red + 30% blue LEDs compared to the other environments including greenhouse conditions. Phytochemical concentrations and a nutritive value of lettuce were also significantly affected by the light treatments. Chlorophyll and carotenoid concentrations increased in the plants grown under 70% red + 30% blue LEDs compared to those grown in the greenhouse. Vitamin C content was 2.25-fold higher in the plants grown under 100% blue LEDs compared to those grown in the greenhouse. Higher photosynthesis and maximal quantum yield of PSII photochemistry were also observed in the plants treated with LED lights. The application of LED light led to the elevated concentrations of macro-and micronutrients in lettuce possibly because of the direct effect of LED light and lower stress conditions in the growth chambers compared to the greenhouse. Although the mechanism of the changes in lettuce grown under LED is not well understood, the results of this study demonstrated that LED light could be used to enhance the growth and nutritional value of lettuce in indoor plant production facilities.     

Isoarnottinin 4′-glucoside, a glycosylated coumarin from Prangos uloptera, with biological activity

Coumarins are a well-known group of natural products distributed in the plant kingdom especially in the family Apiaceae with various biological activities. Isoarnottinin 4′-glucoside is a simple glycosylated coumarin found previously in a few genera of Apiaceae, and its biological activities have not been previously described in details. In the present paper, the compound was isolated from Prangos uloptera (Apiaceae) leaves using HPLC techniques. Antimicrobial, phytotoxic and cytotoxic activities of the compound were evaluated by disk diffusion, lettuce assay and MTT method. Our results indicated that the compound has high antibacterial effect against Erwinia carotovora, a common plant pathogen with MIC value of 100 μg/ml. The compound also exhibited significant phytotoxic activity against lettuce and modest cytotoxic activity against HeLa cell line with IC₅₀ of 0.84 mg/ml. It could be concluded that isoarnottinin 4′-glucoside may play phytoalexin or allelopathic role for plant and may be a candidate for an antibacterial agent or a bioherbicide.     

Over-expression of l-galactono-γ-lactone dehydrogenase increases vitamin C, total phenolics and antioxidant activity in lettuce through bio-fortification

Epidemiological studies have shown that regular consumption of fruits and vegetables is associated with reduced risk of chronic diseases. Vegetables can provide vitamins, phenolics, flavonoids, minerals and dietary fibers for optimal health benefits. However, some nutrients contained in many fruits and vegetables cannot meet of the complete nutrition need in the human body. Biotechnology has the potential to improve the nutritional value of crops. Considering the high consumption of romaine lettuce in human diet worldwide, the objective of study is to enhance the contents of vitamin C, phenolics and antioxidant activity in lettuce leaves by genetic engineering techniques. The gene expression level, vitamin C content, total phenolics, as well as total and cellular antioxidant activities were analyzed by real-time PCR, HPLC, Folin–Ciocalteu, Hydro-PSC and CAA methods, respectively. The bio-fortification of genetically engineered lettuce increased vitamin C up to 48.94 ± 1.34 mg/100 g FW following the increased over-expression of _At GLDH. This is almost a 3.2-fold increase as the content when compared with wild type lettuce (p < 0.05). In addition, phenolic compounds in transgenic lettuce contained 120.4 ± 1.62 mg GA equiv./100 g FW, almost double the phenolic content of the wild type. Total antioxidant activities were 735.4 ± 47.7 μmol vitamin C equiv./100 g FW, cellular antioxidant activities were 7.33 ± 0.86 μmol quercetin equiv./100 g FW (PBS wash) and 18.14 ± 0.68 μmol quercetin equiv./100 g FW (No PBS wash) in transgenic lettuce, respectively, 1.5, 4 and twofold increases when compared with the wild type. This study suggests that bio-fortification by genetic engineering has great potential to improve vitamin C, phenolic contents and antioxidant activity in lettuce.