No abstract

In the coastal region of the Nghe An province, the geomorphology is characterized by appearances of fields of arca granosa with placura placenta and hills of placura placenta with arca granosa, namely: The hills of placura placenta with the arca granosa shells in the Quynh Van and Nghi Tien communes; the fields of arca granosa with the placura placenta: deep-seated in the Quynh Nghia, Dien Chau and along the Nghi Yen coast  which have age of 4,500 - 4,300 yrs.; The appearance of the placura placenta-arca granosa shell’s fields and hills which do not originate from either marine transgression in the Holocene epoch, tectonic movement or artificiality; Our results suggest that there were three tsunami events occurring in the past during the periods of 4,500 - 4,300; 4,100 - 3,900 and 900 - 600 yrs., respectively in the region.

The present study aimed to investigate the in vitro antioxidant and antimicrobial activities of hydrophilic extracts prepared from shallot and garlic bulbs, and their effects on round scad during iced storage. Both the shallot and garlic extracts exhibited antioxidant activity concerning DPPH radical scavenging, total reducing power, and lipid peroxidation inhibition. The extracts also had antimicrobial activity against both Gram-positive (Bacillus cereus, Staphylococcus aureus) and Gramnegative (Escherichia coli, Salmonella typhimurium) pathogenic strains. Effects of treatment with the extracts on quality of round scad were evaluated by monitoring the total lipid hydroperoxides (HPO), thiobarbituric acid reactive substances (TBARS), total volatile basic nitrogen (TVB-N), total viable counts (TVC), and sensory characteristics. The spoilage indicators (HPO, TBARS, TVB-N, TVC) of the round scad treated with either shallot or garlic extracts were significantly suppressed during the ice storage period (P < 0.05). Round scad treated with either shallot or garlic extracts kept their natural sensory characteristics accepted for food-grade longer than 4 days of ice storage, compared with the control (without treatment). These results clearly show that the shallot and garlic extracts are potential natural preservatives, which can extend shelf-life of iced round scad.

Aims and Objective: 1-Alkynes are the important precursors for the CuAAC click chemistry. The hybrid of 1,2,3-triazole ring to the chromene ring and sugar moiety could bring some remarkable biological properties. Propargyl derivatives are usually used in the click chemistry. This article reported the synthesis of 2-amino-4-aryl-7-propargyloxy-4-aryl-4H-chromene-3-carbonitriles using propargyl bromide as alkylation agent and the use of potassium carbonate and sodium hydride as bases in the conversion of 2-amino-4-aryl-7- hydroxy-4-aryl-4H-chromene-3-carbonitriles into corresponding propargyl ethers in Williamson’s ether synthesis. Materials and Methods: The use of CTAB for the synthesis of benzylidene malononitriles and anhydrous potassium carbonate as a catalyst in absolute ethanol in the synthesis of 2-amino-7-hydroxy-4H-chromene-3- carbonitriles is an efficient and simple synthetic method. Propargyl ether compounds of these 4H-chromene-3- carbonitriles were obtained from the alkylation reaction by propargyl bromide. Two procedures were applied: K2CO3 as a base in acetone solvent (Procedure A) and NaH as a base in DMF solvent (Procedure B). The single-crystal X-ray structure of propargyl ether 5e has been studied. Results: The use of K2CO3 and NaH as bases in the Williamson’s ether synthesis from 2-amino-7-hydroxy-4Hchromene- 3-carbonitriles showed that Procedure B was the better route and gave ethers in the higher yields. 2- Amino-4-aryl-7-propargyloxy-4-aryl-4H-chromene-3-carbonitriles were obtained from corresponding 7- hydroxy-4H-chromene-3-carbonitriles. Yields of ethers 5a-i were 70−89% and 80−96%, respectively depending on the used procedures. Conclusion: The described methods are simple, clean and environmentally friendly alternatives for the preparation of 2-amino-4-aryl-7-hydroxy-4H-chromene-3-carbonitriles. The conditions for the transformation of these compounds into propargyl ethers include dried DMF as a solvent, NaH as a base and reaction time of 2 h at the room temperature. A series of 2-amino-4-aryl-7-hydroxy-4-aryl-4H-chromene-3-carbonitriles were obtained based on investigated reaction condition.

Acute Hepatopancreatic Necrosis Disease (AHPND) is a widespread disease targeting cultured shrimps, which results in heavy losses in many regions around the world including Vietnam. The causative agent of the disease is Vibrio paraheamolyticus which is a Gram-negative bacterium present ubiquitously in marine environment. However, this normal floral organism once acquired a plasmid containing Pir- toxin encoding gene (AHPND plasmid) can transform into a highly toxic strain (AHPND strain) with the ability to kill a large number of cultured shrimps in a short period. To understand more on the virulence of V. parahaemolyticus, 17 different V. parahaemolyticus isolates collected from different locations in Southern Vietnam have been analyzed for the presence of AHPND plasmid using PCR method and their extracellular enzyme profile using agar- based method. Seven enzymes which are known to be important virulence factors of the bacterium were studied including caseinase, gelatinase, lecithinase, hemolysin, elastase, lipase and chitinase. Results showed that among 17 studied isolates, six were detected to have AHPND plasmid. Enzymatic activity was observed for caseinase, gelatinase and lecithinase while undetectable for others. The ability to produce these three enzymes varied among different V. parahaemolyticus isolates. Lecithinase appeared in all isolates while the presence of caseinase and gelatinase varied. This indicated that lecithinase seems to be core enzyme of V. paraheamolyticus and the extracellular enzymes do not correlate with the presence of AHPND plasmid. In conclusion, our data suggested that the virulence of Vibrio parahaemolyticus mostly depends on the presence of AHPND plasmid other than extracellular enzymes.