Published: 2020-06-30

Phytochemical analysis of Ardisia silvestris leaf extracts and their antioxidant and antibacterial activities

Hong V. C. Phung, Biet V. Huynh, Toan Q. Truong, Nga T. T. Nguyen, & Phuong T. N. Nguyen
Electronic version: 31 Aug 2020 | DOI: 10.52997/jad.4.04.2020
Abstract | PDF (348K)


The phytochemical analysis and antibacterial and antioxidant activity of Ardisia silvestris extracts were carried out. The bioactive compounds of Ardisia silvestris leaves were extracted with petroleum ether, ethyl acetate, ethanol and water by immersion and microwave method. The DPPH method was used to determine the antioxidant activity of Ar-disia silvestris extracts. The antibacterial properties of Ardisia silvestristested against of Staphylococcu saureus,Samonellasp., and Escherichia coli were determined by using agar diffusion method. The agar diffu-sion method was used to determine the antibacterial effects of both plant extracts on the test organisms. The results showed that Ardisia silvestris leaves contained compounds such as essential oils, fats, alka-loids, flavonoids, coumarins, tannins, anthocyanoids, carotenoids, organicacids, reducing agents, proanthocyanidins, saponins and anthraquinones. Ardisia silvestris leaves had a total polyphenol content of 0.26% dry mat-ter, tannin of 8.8%, and a total flavonoid of 1.44 mg/g. The ethyl acetate extract and water extract of the leaves had the antioxidant activity and were 4.2 and 4.4 times lower than ascorbic acid, respectively. The ethyl acetate extract of Ardisia silvestris had the highest oxidative activity. The zone of inhibition of the plant extract diameters at the concentra-tion of 100μl/ml ranged between 9.67mm and 20.67mm for ethyl acetate and ethanol extracts, respectively on E.coli. Similarly, the zones of in-hibitionof ethyl acetate and ethanol extracts diameters were 14.67 and 15.33 mm, respectively onSamonellasp., however, it was not shown for Staphylococus aureus.

Synthesis and transfer of RNAi construct for potential knock-down of gene expression of root-knot nematode (Meloidogyne graminicola) to rice (Oryza sativa L.)

Phong V. Nguyen, Phuong T. Nguyen, Nhi T. Y. Le, & Loan T. N. Nguyen
Electronic version: 31 Aug 2020 | DOI: 10.52997/jad.5.04.2020
Abstract | PDF (817.6K)


Effectors play key roles in the parasitism of the plant-parasitic nematode. Silencing the effector-coding genes was applied to study the function and role of nematode effectors. In this study, the Mgra16281 gene (ID: MK322955.1) encoding an effector with the unknown function was cloned from the rice root-knot nematode Meloidogyne graminicola isolated in Long An province. To knock-down the ex-pression of this gene, an artificial microRNA was synthesized based on the Osa-MIR528 precursor and inserted into an expression vector. This microRNA can be expressed in rice to investigate the function of MGRA16281 of root-knot nematode via host-induced gene silencing approach (HIGS).

Microencapsulation of Gac (Momordica cochinchinensis Spreng.) fruit oil in Ca-Alginate bead produced through Jetcutter

Vinh Truong, Phuong N. M. Ta, & Phuong T. Nguyen
Electronic version: 31 Aug 2020 | DOI: 10.52997/jad.10.04.2020
Abstract | PDF (666.3K)


The Gac (Momordica cochinchinensisSpreng.) fruit oil was microencapsulated in Ca-Alginate bead by Jetcutter equipment. Experiments showed that the effects of emulsion preparation and equipment parameters were significant on particle size, microencap-sulation yield, loading capacity and solids recovery efficiency of the device. At alginate concentration of 2.5%, the bead had a spherical size of 1.07 - 1.18 mm when the fluid flow was 14 mL/min and the rotation of the cutting disc was 400 - 800 rpm. Samples stored for 2 h after homogenization showed better microencapsulation yield (83 - 84%) and bead size (1.07 mm) than those stored for 24 h after homogenization (79% and 1.18 mm). When the loading capacity increased from 20% to 40%, the mole ratio (CaCl2-alginate) in the bead was reduced from 1.55 to 0.86. This mole ratio data can be considered to control and adjust CaCl2 concentration during the continuous operation of the Jetcutter.

Antimicrobial activity of essential oils on food pathogens

Ngoc T. A. Tong, Tu C. Nguyen, & Ha C. Nguyen
Electronic version: 31 Aug 2020 | DOI: 10.52997/jad.8.04.2020
Abstract | PDF (758.3K)


The study aimed to screen the antibacterial activity of seven types of essential oils against 5 bacteria and 4 strains of E. coli using disk diffusion and MIC method. The essential oils were more effective against Gram-positive bacteria as compared to Gram-negative species. Thyme and cinnamon essential oils showed strong antimicrobial activity against all microorganisms tested. Especially, the tested essential oils inhibited the growth of multi-antibiotics resistant bacteria isolated from food processing chains, indicatingthe possibility of their potential use in reality. The MIC values of cinnamon and thyme essential oils against E. coli ATCC 25922, S. typhimurium, S. aureus, L. monocytogenes and P. aeruginosa were 512-1024 μg/mL and 1024-4096 μg/mL, respectively. The present study provided useful information and showed the potential use of cinnamon and thyme essential oils in food storage as natural antimicrobial preservatives.

Alcoholic fermentation of red flesh dragon fruit (Hylocereus polyrhizus)

Diep T. N. Duong, & Binh Q. Hoang
Electronic version: 31 Aug 2020 | DOI: 10.52997/jad.7.04.2020
Abstract | PDF (412.9K)


The experiment was conducted to determine effects of sodium metabisulfite content, flesh and water mixing ratio, total soluble solids content, percentage of additional yeast and fermentation time on alcoholic fermentation ofred flesh dragon fruit. The results showed that all factors influenced the fermentation. The most appropriate fermentation conditions were use of juice without water mixing, addition sodium metabisulfite content of 80 ppm, the total soluble solid content of 22 oBrix, 5% of yeast solution and 13-d fermentation.

Screening of factors influencing the hydrolysis reaction of chicken leg cartilage with Protamex enzyme as a catalyst

Cuong V. Bui, Chi T. K. Nguyen, & Dong X. Bui
Electronic version: 31 Aug 2020 | DOI: 10.52997/jad.9.04.2020
Abstract | PDF (360.8K)


The objective of this research was to use Protamex enzyme as a cat-alyst to hydrolyze chicken leg cartilage for production of amino acid hydrolysate. The proximate composition of chicken cartilage was analyzed. The results indicated that the major components in the dry matter of chicken leg cartilage were lipid (19.72 ± 0.05%) and protein (13.34 ± 0.08%). The main parameters affecting the hydrolysis reaction of chicken leg cartilage with Protamex enzyme were selected for investigation: reaction temperature (oC), pH, enzyme ratio (%, based on the weight of substrate), reaction time (min), and the ratio of reaction volume (v/v). The significant difference was analyzed by ANOVA One-Way to identify the optimal point of each parameter toward amino acid yield. The results revealed that the hydrolysis degree and amino acid yield reached the maximal values of 22.93 ± 4.01% and 30.25 ± 1.86%, respectively, when the reaction temperature, pH, enzyme ratio, reaction time, and ratio of reaction volume (v/v) were 40oC, 4, 0.52%, 40 min, and 1/18, respectively.

Assessment of salinity intrusion in coastal districts of Ben Tre province using Landsat 8 image

Thinh V. Tran, Lam N. Lo, & Trung V. Le
Electronic version: 31 Aug 2020 | DOI: 10.52997/jad.6.04.2020
Abstract | PDF (553.8K)


Monitoring and evaluation of saline water intrusion is an important task, especially for agricultural production in Ben Tre province. The paper introduces a new solution in the application of Landsat 8 satellite imagery and field survey data to determine the soil electrical conductivity (EC) for soil salinity assessment through the distribu-tion of EC indice value. Analyzing and establishing the correlation between reflectance value, salinity indices and EC allow selecting a suitable model for the creation of a soil salinity map in 4 levels corresponding to EC values: no salinity (0 - 4), mild (4 - 8), moderate (8 - 16), very salinity (> 16). Research results in 2019 showed that most of the coastal districts of Ben Tre province were salty with EC values ranging from 8 to 16. The salinity decreased gradually from the East Sea to the mainland with the distance from 15 to 25 km. In brief, the study proposed solutions for rapid monitoring and evaluation of soil salinity based on the easy access of Landsat 8 images to calculate the necessary indices in the establishment of soil salinity maps for the local and regional scale.

Isolation and identification of lactic acid bacteria from vegetable-growing soils in Da Lat, Lam Dong

Phong V. Nguyen, Thanh T. L. Bien, Vuong V. Le, Hai T. Pham, Mai T. N. Dang, & Nguyen T. T. Nguyen
Electronic version: 31 Aug 2020 | DOI: 10.52997/jad.1.04.2020
Abstract | PDF (1.1M)


Lactic acid bacteria (LAB) have been used for decades in agri-culture to improve soils, control disease and promote plant growth. LAB have been isolated from fermented food, milks and plants, however, a few studies of LAB from soils have been reported. This study aimed to isolate, screen and identify LAB from vegetable-growing soils collected from Da Lat (Lam Dong province). From 33 soil samples, 25 LAB isolates were selected on MRS agar supplemented with 1% CaCO3. The LAB isolates formed small, creamy white, convex, entire margin colonies, and were Gram-positive, catalase-negative and rod-shaped bacteria. Based on the acid-producing capacity, five LAB isolates (DT2, CT3, CC2, XL7 and S2) that produced clear zones around colonies due to the solubilization of CaCO3 with diameters ranged from 1.03 – 1.33 cm, and 11.8 – 14.3 mg/mL acid after 2-day incubation at 30oC. All selected LAB isolates showed the capacity to inhibit the growth of Fusarium oxysporum at level 1 (inhibitory rates in range of 10.66 – 19.96%), and Phytopthora sp. at level 3 (inhibitory rates in range of 50.86 – 57.44%) af-ter 3 days. The isolates did not inhibit against E. coli and Staphylococcus but inhibit the growth of Bacillus spizizenii and Salmonella typhi with average inhibition diameters in range of 3.33 – 4.90 mm and 2.43 – 3.37 mm, respectively, after 1-day incubation. The five LAB isolates were molecularly determined to be Lactobacillus plantarum with 97 – 100% similarities.

Effects of phosphorus fertilizer on growth, yield and quality of coconut at early reproductive stage under saline intrusion condition in Mekong Delta

Nong C. Le, Chuong D. X. Nguyen, Tri D. H. Nguyen, Thu N. Q. Thai, & Thang Q. Luu
Electronic version: 31 Aug 2020 | DOI: 10.52997/jad.3.04.2020
Abstract | PDF (337K)


Coconut palm (Cocos nucifera L.) is one of the most important oil crops in the tropics. The tree is able to grow well under saline intrusion con-dition. However, in the case of high level of salinity for a long period, the coconut tree is severely affected, resulting in poor growth and yield. Therefore, providing balance and sufficient nutrients would help plants tolerate better to unsuitable environment including salinity. Among plant macronutrients, phosphorus is considered to help coconut tree have more roots and leaves, stimulating flowers formation and fruit setting which lead to improve yields. The aim of this work was to determine effects of the amount of phosphorus fertilizer and the frequency of application on growth, yield and quality of coconut tree at early reproductive stage under saline intrusion condition. Two two-factor experiments were con-ducted in Binh Dai district, Ben Tre province and Tan Phu Dong district, Tien Giang province where the highest salinity in the dry season reached 13.8%₀ and 6.3%₀, respectively. The treatments of experiments were ar-ranged in split-plot design (SPD) with three replications. The main plot factor was the frequency of phosphorus fertilizer application (2 and 4 times per year) and the sub-plot factor was the amount of phosphorus fertilizer (30, 45, 60 and 75 kg P2O5/ha/year). The results showed that coconut trees grew best with the treatment of four applications of 60 kg P2O5/ha/year, corresponding to 0.3 kg P2O5/tree/year. The trees in this treatment had more leaves, fruit setting, nut number per tree and higher yield than other treatments under saline intrusion condition.

Effect of nitrogen levels on growth and development of three Lisianthus (Eustomagrandiflorum(Raf.) Shinn) cultivars pot-planted in Ho Chi Minh City

Duong T. T. Pham, Duong H. A. Pham, Huong T. K. Nguyen, Lieu T. Nguyen, & Bao D. Nguyen
Electronic version: 31 Aug 2020 | DOI: 10.52997/jad.2.04.2020
Abstract | PDF (311.1K)


Lisianthus (Eustoma grandiflorum (Raf.) Shinn) is favored in deco-ration because of its long-lasting and colorful flowers. The objectiveof the experiment was to evaluate the effects of different levelsof nitrogen on the growth and development of three Lisianthuscultivars pot-planted in Ho Chi Minh City. The experiment was laidout in split - plot design (SPD) with four levels of nitrogen (3; 4; 5;6 g/pot) being the main factor and three lisianthus cultivars (Pink;Yellow; White/Purple) being the subordinate factor. Each pot wasplanted with one plantlet. The results indicated that plants appliedwith 4.0 g nitrogen per pot gave the best performance in plantheight (18.41 cm) and number of leaves (24.08 leaves/plant) at 60days after planted (DAP). The Pink cultivar reached the highestplant height (19.92 cm), number of leaves (43.53 leaves/plant)as well as number of flowers buds (12.31 buds/plant). The Pinkcultivar, when applied with 4.0 g nitrogen/pot, gave the highestplant height (21.38 cm) at 60 DAP.