Contribution to the characterisation of honey-based Sardinian product abbamele: Volatile aroma composition,honey marker compounds and antioxidant activity

Sardinian abbamele is a typical product obtained from the honey recuperation from combs (traditional procedure) or by concentration of the honey diluted in water (industrial procedure). Seven abbamele samples were obtained to study the volatiles’ composition, the presence of honey marker compounds and their relationship with the production procedures. The long thermal treatment applied in abbamele production caused very high (1007.0–4405.8 mg/kg) HMF content (HPLC-DAD), while glucose and fructose amounts were quite similar to the honey ones (HPLC-RI). Total antioxidant activity (FRAP assay) of the samples ranged between 13.3 and 71.2 mmol Fe²⁺/kg, while antiradical activity (DPPH assay) ranged between 3.8 and 23.3 mmol TEAC/kg. Such high antioxidant values were linearly correlated with total phenol amount (1297.8–4469.5 mg GAE/kg) determined by Folin–Ciocalteau method. Thermally derived furan derivatives and terpenes were abundant among the headspace volatiles (HS-SPME), particularly limonene (0.5–76.0%) that probably originated from citrus rinds’ addition during abbamele production. GC and GC–MS analyses of USE isolates revealed HMF predominance as well as the honey marker compounds (if/when existing) such as methyl syringate (up to 49.2%), marker of Asphodelus microcarpus honey. High isophorone percentage (up to 30.9%) determined by HS-SPME followed by minor percentage of 4-ketoisophorone and norisoprenoids in one sample indicated Arbutus unedo L. honey use in the production. HPLC-DAD analysis confirmed the presence of specific honey markers: two samples showed high methyl syringate concentrations (150.4–120.1 mg/kg) while homogentisic acid and other specific markers of A. unedo honey were found in one sample. The compared GC–MS and HPLC-DAD data proved to be useful to obtain information about the use of specific honey in the production and to verify citrus addition.     

Chemical constituents of Angiopteris esculenta including two new natural lactones

Angiopteris species (Angiopteridaceae) have been widely used in traditional Chinese medicine to treat many diseases. A.esculenta Ching was endemic to north-west of Yunnan Province, China, its rhizomes were used as a foodstuff by the local people for the extraction of starch. From the extracts of the aerial parts of the plant, two new natural lactones (5R,6R)-5,6-dihydro-5-hydroxy-6-methyl-2H-pyran-2-one (1) and (5R,6R)-5-(1-hydroxyethyl)-2(5H)-furanone (2), two known lactones, (5R,6R)-5-(1-hydroxyethyl)-dihydro-2-furanone (3) and angiopteroside (4), and six known compounds, coumarin (5), 5-(hydroxymethyl)furfural (6), 9(11)-fernene (7), β-sitosterol (8), d-fucose (9) and l-arabinose (10) were isolated and identified by using combination of mass spectrometry and various 1D and 2D NMR techniques. This is the first report of the chemical constituents of A. esculenta.     

Short communication: Biofilm production characterization of mecA and mecC methicillin-resistant Staphylococcus aureus isolated from bovine milk in Great Britain

Staphylococcus aureus is an important cause of contagious intramammary infection in dairy cattle, and the ability to produce biofilm is considered to be an important virulence property in the pathogenesis of mastitis. The aim of this study was to characterize the biofilm formation capacity of methicillin-resistant Staph. aureus (MRSA), encoding mecA or mecC, isolated from bulk tank milk in Great Britain. For this purpose, 20 MRSA isolates were grown on microtiter plates to determine the biofilm production. Moreover, the spa-typing and the presence of the intercellular adhesion genes icaA and icaD were analyzed by PCR. All MRSA isolates tested belonged to 9 spa-types and were PCR-positive for the ica genes; 10 of them (50%) produced biofilm in the microtiter plate assay. This is also the first demonstration of biofilm production by mecC MRSA.     

Chemical and biological characteristics of Cuminum cyminum and Rosmarinus officinalis essential oils

Essential oils extracted by hydrodistillation from Cuminum cyminum and Rosmarinus officinalis were characterized by means of GC and GC–MS. C. cyminum and R. officinalis contained α-pinene (29.1%, 14.9%), 1,8-cineole (17.9%, 7.43%) and linalool (10.4%, 14.9%), respectively, as the major compounds. C. cyminum oil exhibited stronger antimicrobial activity than did R. officinalis oil against E. coli, S. aureus and L. monocytogenes. Complete death time on exposure to Cuminum cyminum L. and Rosmarinus officinalis L. oils were 20 and 25 min 180 and 240 min and 90 and 120 min for E. coli, S. aureus and L. monocytogenes, respectively. Radical-scavenging and antioxidant properties were tested by means of 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay and the β-carotene bleaching test. These properties were compared to those of Thymus x-porlock essential oil, used as a reference ingredient. The radical scavenging performance of the rosemary oil was better than that of C. cyminum. Results from the antioxidant test were better than those provided by the radical-scavenging activity. C. cyminum and R. officinalis essential oils may be considered as potent agents in food preservation.     

Properties and safety aspects of Enterococcus faecium strains isolated from Chungkukjang, a fermented soy product

Enterococcus faecium isolated from Chungkukjang, a Korean traditional fermented soybean food was studied for their functional characteristics as potential new starter culture and safety. Microbiological analysis of ripened Chungkukjang revealed the presence of an enterococcal population in numbers of up to 6 log CFU per g. Seven isolates with higher activity were selected for further study and the strains were identified as E. faecium. The E. faecium strains showed resistance against simulated gastrointestinal conditions such as acidic environment and the presence of bile salts. These strains also showed bile salt hydrolase activity but neither hemolytic activity nor virulence determinant such as gelE and efaAfm. All strains were susceptible to glycopeptides and lacked potential as vancomycin-resistant enterococci (VRE). Two strains, S2C10 and S2C11, showed inhibited the viability of Listeria monocytogenes in vitro. The ability was probably due to the production of bacteriocin. The lipase activity influenced the stability, while either acidic condition or high temperature did not play a significant role in the activity of the antimicrobial substances. The strains also produced thermostable listericidal antimicrobial substance. For this reason, the strains could be used as selected starters or protective cultures in soybean fermented food production.     

Tyrosinase inhibitory activity of native plants from central Argentina: Isolation of an active principle from Lithrea molleoides

Screening of 91 native plants from central Argentina was carried out with the aim of finding new sources of anti-tyrosinase compounds. Extracts obtained from Achyrocline satureioides, Artemisia verlotiorum, Cotoneaster glaucophylla, Dalea elegans, Flourensia campestris, Jodina rhombifolia, Kageneckia lanceolata, Lepechinia floribunda, Lepechinia meyenii, Lithrea molleoides, Porlieria microphylla, Pterocaulon alopecuroides, Ruprechtia apetala, Senna aphylla, Sida rhombifolia, Solanum argentinum, Tagetes minuta and Thalictrum decipiens exhibited more than 90% inhibition of tyrosinase monophenolase activity at 1000 μg ml⁻¹. D. elegans,L. meyenii and L. molleoides were the most potent with IC₅₀ values of 0.48, 10.43 and 3.77 μg ml⁻¹, respectively. D. elegans, L. molleoides and T. decipiens also showed more than 90% inhibition of diphenolase activity at 1000 μg ml⁻¹, with the first of these being the most effective (IC₅₀ = 49.27 μg ml⁻¹). (Z,Z)-5-(trideca-4,7-dienyl)-resorcinol (1) was isolated from L. molleoides as an effective tyrosinase inhibitor with l-tyrosine or l-DOPA as substrates (IC₅₀ = 0.49 and 14.94 μg ml⁻¹, respectively). Compound 1 was 37 times more active in monophenolase inhibitory activity than kojic acid used as a reference. Effective extracts as well as (Z,Z)-5-(trideca-4,7-dienyl)-resorcinol could prove to be promising preservative agents for use in the food industry.     

Chemical characterization of Chinese chive seed (Allium tuberosum Rottl.)

Chinese chive seeds (Allium tuberosum Rottl.) (grown in China) were investigated. Density, thousand-grain weight, and hectolitre weight of seeds were 1.27 g/cm³, 4.9 g, and 71 kg/100 l, respectively. The results showed that Chinese chive seeds contained high amounts of oil (15.8%), dietary fibre (18.2%) and crude protein (12.3%). Oil of seeds was composed of 10.1% saturated and 90.0% unsaturated fatty acids. Linoleic(69.1%) and palmitic (7.0%) were the most abundant unsaturated and saturated fatty acids, respectively. Chinese chive seeds contained 4.5 mg/kg of thiamin, 2.8 mg/kg of riboflavin and 55.1 mg/kg of niacin. The mineral contents of the seed of A. tuberosum, for iron, calcium and zinc, were 580 mg/kg, 1328 and 80.8 mg/kg, respectively. Analysis of the amino acid content of Chinese chive seed revealed that it was a rich source of the essential amino acids, isoleucine, tryptophan and lysine. The study revealed that Chinese chive seeds had high levels of nutritionally important components, such as oil, minerals and essential amino acids.     

Progress towards a lure to attract three stored product weevils, Sitophilus zeamais Motschulsky, S. oryzae (L.) and S. granarius (L.) (Coleoptera: Curculionidae)

The behavioural responses of Sitophilus granarius, S. oryzae and S. zeamais to synthetic 4S,5R-sitophinone alone and in combination with volatiles from kibbled carob have been investigated with a view to the development of a single lure to attract all three species. Sitophilus zeamais and S. oryzae were shown to respond to 4S,5R-sitophinone at amounts as low as 0.025 ng. Sitophilus granarius gave a significant response to 50 ng 4S,5R-sitophinone. Volatiles from kibbled carob were also shown to attract all three species. This is the first time that attraction of S. zeamais and S. oryzae to carob volatiles has been demonstrated. Fresh lures containing 4S,5R-sitophinone and carob volatiles attracted significantly more insects in pitfall bioassays for all three species than when either component was used alone. However, after 6 weeks a significant increase in response compared to the control was found only for S. oryzae and S. zeamais. The effect of insect age on response to the pheromone and carob volatiles was also studied for all three species. The response to carob volatiles decreased with increasing insect age for all three species. A significant response to 4S,5R-sitophinone was found only for 1-2-day-old adults of S. oryzae and S. zeamais but for all ages tested of S. granarius. The effect of the combination of pheromone and carob volatiles also decreased with increasing insect age.     

Antifungal activity of the honey flavonoid extract against Candida albicans

Candida albicans is the most prevalent dimorphic pathogen in humans. We investigated the potential protective effect of honey flavonoid extract (HFE) on Candida dimorphism induced by RPMI 1640 medium. Yeast to hyphal transition was dose dependently prevented when Candida cultures were treated with HFE for 6 h (germ-tube formation) and 18 h (hypha elongation). Since during hyphal growth remarkable amounts of reactive oxygen species (ROS) are generated, we investigated whether HFE affects the generation of ROS, the glutathione level and the activity of glutathione-dependent enzymes. Treatment of Candida cells with 48 μg/ml (MIC₅₀) of HFE for 6 or 18 h inhibited the dimorphic conversion by supporting of the intracellular glutathione level. HFE exerts a dual protective effect inhibiting both ROS generation during germ-tube formation and γ-glutamyltranspeptidase activity, responsible for GSH degradation, during hypha elongation. These results show that HFE confers a significant protection against yeast to hyphal transition of C. albicans.     

Diversity of culturable microorganisms and occurrence of Listeria monocytogenes and Salmonella spp. in Tuber aestivum and Tuber melanosporum ascocarps

The aim of this study was to investigate the total mesophilic microorganisms, Pseudomonas genus, Enterobacteriaceae family, mold and yeast counts and the presence of Listeria monocytogenes and Salmonella spp on Tuber aestivum and Tuber melanosporum ascocarps. The results confirmed that the major percentage of the microorganisms, approximately 9.0 log ufc/g, were present in the peridium, the glebas of healthy truffles being practically free of microorganisms. The predominant microbial group was the Pseudomonas averaging 8.3 and 8.4 log cfu/g on T. aestivum and T. melanosporum whole ascocarps, respectively. The Enterobacteriaceae also achieved high populations, especially in T. aestivum truffles, with 6.3 log cfu/g. Molds and yeasts never exceeded 5.0 log cfu/g. The characterization of the isolates revealed that the fluorescens pseudomonads were the most prevalent. Raoultella terrigena and Enterobacter intermedius were the dominant Enterobacteriaceae. The identification of the yeast isolates revealed five species: Debaryomyces hansenii, Issatchenkia scutulata, Rhodotorula aurantiaca, Saccharomyces dairensis and Trichosporon beigelii subspecies A and B. The mold genera detected in both species of truffles were Aspergillus, Cladosporium, Penicillium and Fusarium, Trichoderma being present only in T. aestivum. L. monocytogenes was found in 10% of the samples of T. aestivum analysed but Salmonella spp. was not detected. Knowledge of the microbial population in terms of possible food borne and pathogen microorganisms is very useful for establishing successful disinfection and storage methods to prolong the shelf-life of ascocarps of T. aestivum and T. melanosporum.     

Chemical composition and biological activities of Algerian Thymus oils

The compositions of essential oils isolated from nine samples of three Thymus species (Thymus algeriensis, Thymus pallescens and Thymus dréatensis) were analysed by GC and GC–MS, and a total of 114 components were identified. T. pallescens collected from various regions showed a great similarity in their compositions and were characterised by carvacrol (44.4–57.7%), p-cymene (10.3–17.3%) and γ-terpinene (10.8–14.2%) as the major components for four samples; only one sample was thymol-rich (49.3%) with a small amount of carvacrol (9.0%). On the other hand, T. algeriensis showed a chemical polymorphism, even for samples from the same location, and two new chemotypes for this species were proposed. Oxygen-containing monoterpenes were the predominant class (76.3%) in T. dreatensis oil, with linalool (30.4%), thymol (20.2%) and geraniol (19.6%) as the principal constituents. The oils were screened for their possible antioxidant activities by four complementary assays, namely DPPH free radical scavenging, hydroxyl radical scavenging, inhibition of lipid peroxidation and reducing power. The two new chemotypes of T. algeriensis exhibited strong hydroxyl radical scavenging (IC₅₀ = 2.2–3.3 μg/ml), but were not or only slightly active against the other radicals and exhibited a weak reducing power. Despite their chemical similarity, T. pallescens oils sometimes produced significant differences in their antioxidant activities. The essential oils were also screened for their antimicrobial activity against five bacteria (three Gram-positive and two Gram-negative) and one yeast (Candida albicans). The tested essential oils showed antimicrobial activity against the microorganisms used, in particular against two important pathogens, C. albicans and Helicobacter pylori.     

Effect of damaged starch on acrylamide formation in whole wheat flour based Indian traditional staples, chapattis and pooris

Variation in acrylamide content of two Indian traditional products, chapatti and poori was observed with respect to the damaged starch content in whole wheat flour of different wheat varieties from which these products were prepared. Wheat cultivar ‘lokwan’ was milled by altering mill aperture, feed rate and moisture content to obtain whole wheat flour with damaged starch contents ranging from 6.23% to 28.12%. Acrylamide content of the chapatti and pooris prepared from such flours ranged from 12.5 to 65.5 μg/kg in chapatti, and 25.5 to 130.5 μg/kg in pooris. Impact of several additives showed 10 μmol/g flour citric acid, and 100 μmol/g flour calcium chloride to reduce acrylamide in pooris by approximately 54% and 72%, respectively, without altering the sensory analysis of the products.     

Chemical properties and antiulcerogenic activity of a galactomannoglucan from Syagrus oleracea

A galactomannoglucan (GMG) with an estimated weight–average molar mass of 415,000 g/mol was obtained from an aqueous extract of the mesocarp of fruits of Syagrus oleracea (Mart.) Becc. by fractionation by Sephacryl S-300 HR and Sephadex G-25. Chemical and spectroscopic studies indicated that GMG has a chain of (1 → 4)-linked β-d-mannopyranosyl residues attached to an initial chain of (1 → 3)-linked β-d-galactopyranosyl residues and a terminal chain of (1 → 4)-linked α-d-glucopyranosyl residues which comprised galactose, mannose and glucose in the molar ratio of 30:33:37. Results of the present study indicated that the polysaccharide GMG of S. oleracea significantly inhibited gastric lesions induced by ethanol, showing a gastroprotective property.     

Chemical composition and DSC thermal properties of two species of Hylocereus cacti seed oil: Hylocereus undatus and Hylocereus polyrhizus

Two types of pitaya (Hylocereus cacti) seeds (Hylocereus undatus and Hylocereus polyrhizus) were investigated in this study. The fatty acid, phenolic, tocopherol, and sterol contents of the extracted seed oil were analysed. The results showed that the pitaya seeds contained a high amount of oil (18.33–28.37%). The three major fatty acids in the H. undatus seed oil (WFSO) and H. polyrhizus seed oil (RFSO) were linoleic, oleic, and palmitic acids. The total tocopherol contents in the WFSO and RFSO were 36.70 and 43.50 mg/100 g, respectively. The phytosterol compounds identified in the WFSO and RFSO were cholesterol, campesterol, stigmasterol, and β-sitosterol. Seven phenolic acid compounds were identified in the WFSO and RFSO, namely, gallic, vanillic, syringic, protocatechuic, p-hydroxybenzoic, p-coumaric, and caffeic acids. WFSO and RFSO can be differentiated by their T_off and T_on values in the DSC thermal curves. This study reveals that pitaya seed oil has a high level of functional lipids and can be used as a new source of essential oil.     

Isolation and characterization of a novel analyte from Bacillus subtilis SC-8 antagonistic to Bacillus cereus

In this study, an effective substance was isolated from Bacillus subtilis SC-8, which was obtained from traditionally fermented soybean paste, cheonggukjang. The substance was purified by HPLC, and its properties were analyzed. It had an adequate antagonistic effect on Bacilluscereus, and its spectrum of activity was narrow. When tested on several gram-negative and gram-positive foodborne pathogenic bacteria such as Salmonella enterica, Salmonella enteritidis, Staphylococcus aureus, and Listeria monocytogenes, no antagonistic effect was observed. Applying the derivative from B. subtilis SC-8 within the same genus did not inhibit the growth of major soybean-fermenting bacteria such as Bacillus subtilis, Bacillus licheniformis, and Bacillus amyloquefaciens. The range of pH stability of the purified antagonistic substance was wide (from 4.0 to >10.0), and the substance was thermally stable up to 60 °C. In the various enzyme treatments, the antagonistic activity of the purified substance was reduced with proteinase K, protease, and lipase; its activity was partially destroyed with esterase. Spores of B. cereus did not grow at all in the presence of 5 μg/mL of the purified antagonistic substance. The isolated antagonistic substance was thought to be an antibiotic-like lipopeptidal compound and was tentatively named BSAP-254 because it absorbed to UV radiation at 254 nm.     

Polyphenols and triterpenes from Chaenomeles fruits: Chemical analysis and antioxidant activities assessment

Mugua, fruit of the genus Chaenomeles, is a valuable source of health food and Chinese medicine. To elucidate the bioactive compounds of five wild Chaenomeles species, extracts from fresh fruits were investigated by HPLC-DAD/ESI-MS/MS. Among the 24 polyphenol compounds obtained, 20 were flavan-3-ols (including catechin, epicatechin and procyanidin oligomers). The mean polymerisation degree (mDP) of procyanidins was examined by two acid-catalysed cleavage reactions; the mDP value was the highest in Chaenomeles sinensis and the lowest in Chaenomeles japonica. Total polyphenol content (TPC) reached 46.92 and 46.28 mg/g gallic acid equivalents (GAE) in Chaenomeles speciosa and Chaenomeles thibetica, respectively, although their main bioactive compounds were different (being epicatechin and procyanidin B2 in the former, and catechin and procyanidin B1 in the latter). These two species also exhibited equally strong free radical scavenging activities. Our results further showed that the antioxidant ability of Chaenomeles fruits was significantly correlated to their total polyphenol contents. Two triterpenes (oleanolic acid and ursolic acid) were the highest quantity in Chaenomeles cathayensis and C. thibetica, respectively.     

Efficacy of powder and essential oil from Chenopodium ambrosioides leaves as post-harvest grain protectants against six-stored product beetles

Powder and essential oil obtained from dry ground leaves of Chenopodium ambrosioides were tested under laboratory conditions (25±1°C, 70-75% r.h.) for their ability to protect grains from damage by six insect pests, Callosobruchus chinensis, C. maculatus, Acanthoscelides obtectus, Sitophilus granarius, S. zeamais and Prostephanus truncatus. The insects were reared and tested on whole maize grain for S. zeamais and P. truncatus, whole wheat for S. granarius, green peas for C. chinensis, mung bean for C. maculatus and white bean for A. obtectus. The powder prepared from dry leaves of C. ambrosioides was mixed with grains at different dosages ranging from 0.05-0.80% (wt/wt) for C. chinensis, C. maculatus and A. obtectus and from 0.8-6.4% (wt/wt) for S. granarius, S. zeamais and P. truncatus. The dosage of 0.4% killed more than 60% of all the bruchids 2 days after treatment, while a dosage of 6.4% induced total mortality of S. granarius and S. zeamais within the same exposure time. All levels of the dry ground leaf concentrations inhibited F1 progeny production and adult emergence of the tested insects. The dosage of 0.2 μl/cm² of the essential oil killed 80-100% of the beetles within 24 h except C. maculatus and S. zeamais, where this dosage induced only 20% and 5% mortality, respectively. These results indicate a scientific rationale for the use of this plant in grain protection by local communities in the western highlands of Cameroon.