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• Phenolic Extracts from Myrtaceae Leaves Improve the Quality and Shelf-life of Pacific Whiteleg Shrimp

  Lai Thi Ngoc Ha, Tran Thi Hoai, Nguyen Van Lam, Hoang Lan Phuong

  Received: Aug 04, 2022 / Published: Dec 30, 2022

   Abstract PDF

  This study aimed to quantify the phenolic contents and the antioxidant capacities of leaf extract powders from three Myrtaceae plants, namely Cleistocalyx operculatus (Vietnamese name: Vối), Psidium guajava (Ổi), and Rhodomyrtus tomentosa (Sim), investigate their inhibitive activities on the growth of bacteria isolated from spoiled shrimps, and evaluate their values as preservative agents in the cold storage of Pacific whiteleg shrimps (Penaeus vannamei). The extract leaf powders from R. tomentosa, C. operculatus, and P. guajava had high phenolic contents of 281.25, 282.36, and 349.51 mg gallic acid equivalent/g leaf extract, respectively. Among the three plants, the extract powders of R. tomentosa and P. guajava leaves had the highest antioxidant capacities (about 4 mmol Trolox equivalent (TE)/g) followed by the one of C. operculatus (2.85 mmol TE/g). These three extract powders showed significant antibacterial activities against the seven bacteria isolated from cold-stored spoiled whiteleg shrimps with the inhibition zones ranging from 0.33 to 19.67mm depending on the extract concentration. Among the three leaf extracts, the one from P. guajava leaves showed the highest inhibitive activity. Aeromonas sp2 was the most sensible to Myrtaceae leaf extracts while Aeromonas sp4 was the least affected strain. All the extracts showed high inhibitive activities against melanosis, volatile nitrogen-containing compounds formation, lipid oxidation, and microbial growth in stored shrimps, thereby prolonging the shelf-life of the shrimps. The results suggested the potential application of these three Myrtaceae plants as sources of antioxidant and antimicrobial agents in the cold storage of shrimps.

• Phytochemical Analysis and Antioxidant and Alpha-glucosidase Inhibitory Activities of the Stem Bark of Dialium cochinchinense Pierre

  Tran Thi Thu Trang, Lai Thi Ngoc Ha, Doan Thi Thuy Ai, Nguyen Thi Hien, Nguyen Thi Thu Tram, Vu Thi Huyen

  Received: Jun 18, 2020 / Published: Mar 30, 2022

   Abstract PDF

  The purpose of this study was to determine the phytochemical compositions and to evaluate the biological activity of the stem bark of Dialium cochinchinense. The phytochemical analysis showed the presence of steroids, terpenoids, anthraquinones, saponins, and phenolics in the stem bark of D. cochinchinense. The optimal extraction conditions were 70% ethanol at 30°C for 40min with a material/solvent ratio of 1/20. Under the optimal conditions, the corresponding predicted response value for the total phenolic content was 100.80 ± 0.40 mg GAE/g DW. The evaluation of antioxidant activity indicated that the polyphenol-rich extract was a good source of antioxidants as measured by the DPPH assay with the IC50 of 3.81 ± 0.58 μg mL-1. The extract also demonstrated a strong a-glucosidase inhibitory activity with the IC50 value of 2.14 ± 0.05 μg/mL. Therefore, D. cochinchinense could be useful as a potential preventive intervention for free radicals in mediated diseases as well as an antioxidant drug and a potential source in treating diabetes mellitus in the pharmaceutical industry.

• Optimization of Chlorogenic Acid Extraction from Green Coffee Beans Using Response Surface Methodology

  Lai Thi Ngoc Ha, Nguyen Viet Phuong, Tran Thi Hoai, Dao Thi Viet Ha, Hoang Hai Ha

  Received: Apr 10, 2019 / Published: Jun 06, 2019

   Abstract PDF

  Chlorogenic acid is a natural antioxidant that is widespread in the plant kingdom and can be found at a high content level in green coffee beans. This secondary metabolite in green coffee beans has potent biological properties including antioxidant, anti-inflammatory, anti-cancer, anti-obesity, anti-hypertension, and anticonvulsant. In this study, the extraction of chlorogenic acid from Vietnamese green coffee beans was optimized using the response surface methodology. A second-order polynomial model with three important variables (liquid-to-solid ratio, temperature, and extraction time) was used. A rotatable central composite design consisting of 21 experimental runs with three replicates at the center point was applied to describe the experimental data. The experimental results properly conformed to the constructed model (R2 = 0.8549). The optimized conditions were as follows: 40% ethanol (v/v), a liquid-to-solid ratio of 11.77, at 85oC for 64 min. Four extractions were performed in parallel using the optimal conditions to validate the model. The experimental values highly agreed with the predicted value (P <0.05).

• Agronomic Characteristics, Anthocyanin Content, and Antioxidant Activity of Anthocynins Extracted from the Seeds of Black Rice Accessions

  Phan Thi Thuy, Nguyen Quoc Trung, Do Thi Huong

  Received: Jan 08, 2019 / Published: Feb 13, 2019

   Abstract PDF

  The objectives of this study were to investigate the morphological characteristics, grain yield, and anthocyanin content of 36 black rice accessions that were collected from different locations in Vietnam. The results showed that the black rice accessions varied in growth duration (130 to 150 days), plant height (91.5 to 143.6 cm), morphological characteristics, and yield components. Grain yield of the black rice accessions ranged from 2.8 to 8.7 tons ha-1. The black rice accessions were classified into four groups based on their anthocyanin content: group I > 0.1% anthocyanin, group II 0.05%-0.1%, group III 0.001%-0.05%, and group IV < 0.001%. BR7 had the highest anthocyanin content (0.1438%), followed by BR5 (0.1317%). Anthocyanins with the strongest antioxidant activities were extracted from BR8, BR35, BR6, BR27, BR30, BR32, BR18, BR17, BR19, and BR1 with IC50 values less than 2 µg mL-1. Seven promising black rice accessions, namely BR1, BR14, BR17, BR25, BR30, BR34, and BR35, were selected for further research based on their high anthocyanin contents, and good grain yield and yield components.

• Exploitation of Catechin Extract from Pruned Tea Leaves as a Promising Food Preservative Against Lipid Oxidation

  Lai Thi Ngoc Ha, Tran Thi Hoai, Hoang Lan Phuong, Nguyen Van Lam

  Received: Jun 19, 2023 / Published: Mar 29, 2024

   Abstract PDF

  In Vietnam, a tea-producing country, the tea buds and top three leaves are normally used for tea production while older leaves are pruned and discarded as agricultural waste in the winter. The present study aimed to exploit catechins from pruned tea leaves and use them as natural antioxidants for applications in the food industry. Catechins were analyzed using the guideline of ISO 14502-2-2005 by HPLC-MWD. The contents of catechins in pruned tea leaves of ten popular tea varieties were relatively high, ranging from 65.57 to 136.88 mg/g dry weight. The optimized conditions for catechin extraction from Phuc Van Tien pruned tea leaves (one of the varieties with a high catechin content) were found using response surface methodology as follows: a liquid-to-solid ratio of 21.6/1 at 70oC for 31 minutes. The catechin-rich extract powder was added to sesame oil to inhibit lipid oxidation. During oil accelerated oxidation at 60oC, the catechin-rich extract powder inhibited the increase of the peroxide value compared with the negative and positive controls (no preservative and added tert-butylhydroquinone, respectively). Significant positive correlations between the decrease of catechin content and the inhibition of peroxide formation (r = 0.91, 0.94, 0.95, 0.97, and 0.96 for catechin, epigallocatechin gallate, epigallocatechin, epicatechin gallate, and epicatechin, respectively, P <0.05) proved that the inhibition of peroxide formation in the sesame oil was essentially due to the antioxidant capacity of the catechins in the pruned tea leaf extract. Catechin extracts from pruned tea leaves are potential sources of natural antioxidants for oil preservation.

• Chemical constituents of leaves Dialium cochinchinense Pierre

  Vu Thi Huyen, Doan Thi Thuy Ai, Nguyen Thi Hien

  Received: Sep 30, 2020 / Published: Oct 28, 2021

   Abstract PDF

  The genus Dialium belongs to the Caesalpinioideae family, consisting of approximately 30 species distributed in the tropical regions. Secondary metabolites from the  Dialium genus have been reported to exhibit various biological activities including antioxidant, cytotoxicity and antimicrobial activities. This work describes the isolation and characterization of five compounds from the leaves of Dialium cochinchinense Pierre. Their structures were established by spectroscopic analysis, including MS and NMR spectra. Accordingly, the isolated compounds were identified to be lupeone (1), b-sitostenone (2), β-sitosterol (3), daucosterol (4), and dihydrokaempferide (5). To the best of our knowledge, this is the first report of the isolation of compounds 1 and 5 from the genus Dialium.

• Investigating the Potential of Vietnamese Tea Seed Oil (Camellia sinensis O.Kuntze) for the Enhancement of Oxidative Stability in Vegetable Oils

  Phan Thi Phuong Thao, Tran Thi Thu Hang, Pham Le Nguyet Anh, Vu Hong Son

  Received: Mar 06, 2020 / Published: Jun 18, 2021

   Abstract PDF

  This study examined the effectiveness of different antioxidative compounds, namely 0.2% BHA (Butylated hydroxyanisole) + BHT (butylated hydroxytoluene), 0.03% α – tocopherol, and 3% and 6% tea seed oil (TSO) on the oxidative stability of vegetable oils. Four commonly used oils, viz. rapeseed oil (RSO), peanut oil (PNO), sunflower oil (SFO),  and soybean oil (SBO), were assessed by the Schall Oven test method and monitored during the 12-day preservation period under 60°C. The total oxidation values (TOTOX) of the samples treated with 6% TSO were lower than those treated with 0.2% BHA+BHT. The results indicated the potential of TSO as a novel natural antioxidant for dietary vegetable oils. Our study also suggested that TSO could serve as an effective substitution for currently used synthetic antioxidants such as BHA and BHT.