Polymer-based hydrogels are hydrophilic polymer networks with crosslinks widely applied for drug delivery applications because of their ability to hold large amounts of water and biological fluids and control drug release based on their unique physicochemical properties and biocompatibility. Current trends in the development of hydrogel drug delivery systems involve the release of drugs in response to specific triggers such as pH, temperature, or enzymes for targeted drug delivery and to reduce the potential for systemic toxicity. In addition, developing injectable hydrogel formulations that are easily used and sustain drug release during this extended time is a growing interest. Another emerging trend in hydrogel drug delivery is the synthesis of nano hydrogels and other functional substances for improving targeted drug loading and release efficacy. Following these development trends, advanced hydrogels possessing mechanically improved properties, controlled release rates, and biocompatibility is developing as a focus of the field. More complex drug delivery systems such as multi-drug delivery and combination therapies will be developed based on these advancements. In addition, polymer-based hydrogels are gaining increasing attention in personalized medicine because of their ability to be tailored to a specific patient, for example, drug release rates, drug combinations, target-specific drug delivery, improvement of disease treatment effectiveness, and healthcare cost reduction. Overall, hydrogel application is advancing rapidly, towards more efficient and effective drug delivery systems in the future.

The phlorotannin content and the total antioxidant, reducing power and DPPH free-radical-scavenging activities in relation to postharvest storage time of six Sargassum species (Sargassum mcclurei, Sargassum polycystum, Sargassum oligocystum, Sargassum serratum, Sargassum aquifolium, and Sargassum denticarpum) commonly found growing in the tropical marine area of Nhatrang, Khanhhoa Province, Viet Nam, were investigated. The results showed that phlorotannin content with total antioxidant and reducing power activity, and DPPH free radical scavenging of Sargassum aquifolium species were the highest, corresponding to 6.770± 0.001 mg phlorotannin g −1 DW, 6.1290±0.0200 mg ascorbic acid g −1 DW, 19.7210±0.0300 mg FeSO 4 g −1 DW and 76.28± 0.20 % of 25 μg DPPH mL −1 extract. The change (decline) of phlorotannin content with antioxidant activities in Sargassum polycystum occurs the fastest. The storage time of the algae descends in the following species order such as S. oligocystum>S. mcclurei, S. aquifolium>S. serratum> S. denticarpum>S. polycystum.

Introduction: This study focused on the discussion of effect of various extraction conditions for phlorotannin content and antioxidant activities extracted from brown algae Sargassum serratum. The algae was grown in the tropical coastal areas of Vietnam. Methods: The various extraction conditions include the following parameters: temperature (30-80 0 C), maceration time (1/2-2,5 hours; 8-48 hrs), the ratio of solvent to material (10:1-70:1 (v/w)), pH (2-8), various kind of solvents (ethanol, acetone, chloroform, ethyl acetate and n-hexan) and solvent concentrations. Phlorotannin content, antioxidant activities, and some phytochemical compositions of Sargassum serratum were evaluated. Results: The highest phlorotannin content and antioxidant activities was expressed when extracting in the following conditions: 100% ethanol solvent at 50 0 C in 32 hours with the ratio of solvent to material of 40/1 (v/w), pH 7 and one-step extraction. The extract contained flavonoid, terpenoid, alkaloid, fatty and oil. DPPH free radical scavenging of the extract was 87.53%. Conclusion:Phlorotannin content and antioxidant activities extracted from Sargassum serratum was depended on the extracting conditions. The condition of extraction for antioxidant phlorotannin and the chemical composition of extract was determined. Brown algae Sargassum serratum has high antioxidant phlorotannin content. A total of 6 compounds were identified from the extract of Sargassum serratum.Key words: Antioxidant, Brown algae, Extraction, Phlorotannin, Sargassum. Correspondence :Vu Ngoc Boi, Nhatrang University, Ministry of Training and Education Nguyen Dinh Chieu street, Nhatrang city, Khanhhoa province, VIETNAM. 100%; the ratio of ethanol solvent to sample of 10:1, 20:1, 30:1, 40:1, 50:, 60:1 and 70:1 (v/w); different temperatures of 30, 40, 50, 60, 70 and 80°C; different times 0.5, 1.0, 1.5, 2.0, 2.5, 8.0, 16.0, 24.0, 32.0, 40.0 and 48.0 h; pH of 2, 3, 4, 5, 6, 7 and 8; and the repeat of extracting times in choiced condition. The extract were then centrifuged at 2500 rpm for 10 mins at 4°C and filtered with Whatman no. 4 filter paper, and analysed. Determination of total phlorotannin content (PC)The total phlorotannin content (PC) of extracts was quantified according to the Folin-Ciocalteu's method. 20 300 μL of extracts was mixed with 1 mL of 10% Folin-Ciocalteu reagent. After keeping the mixture for 5 mins, 2 mL of 10% sodium carbonate was added. The samples were incubated for 1.5 h at room temperature in the dark. The absorbance was measured at 750 nm. Phloroglucinol was used as the standard. The results were expressed as milligrams of phloroglucinol equivalents (PGEs) per g dry weight of sample. Total antioxidant activityTotal antioxidant activity (TA) of extracts was determined according to the method of Prieto et al. (1999).21 100 µL of extracts was mixed with 3 mL of reagent (0.6 M sulfuric acid, 28 mM sodium phosphate and 4 mM ammonium molybdate) and 900 µL of distilled water. The samples were incubated at 95°C for 90 min in water ba...

Euphorbia tirucalli is a medicine plant possessing many bioactive properties. This paper focused on phytochemical screening (alkaloid, flavonoid, saponin, tannin, and anthraquinone), quantification of polyphenol and flavonoids, and activating evaluation of antioxidants and antimicrobial properties against Xanthomonas axonopodis of different extracts from Euphorbia tirucalli grown in Binh Thuan, Vietnam. The best activity fraction was used for purification and determining bioactive ingredients. The results showed that the phytochemical study revealed the presence of alkaloids, flavonoids, tannins, and terpenoids in the ethyl acetate fraction. Saponin and anthraquinone did not present in all extracts. The content of polyphenol and flavonoid of Euphorbia tirucalli stem was in the range of 16.65–106.32 mg EqAG/g and 97.97–450.83 μg QE/g. The ethyl acetate fraction showed higher amounts of polyphenol and flavonoids and antimicrobial activity against X. axonopodis than other fractions. The antioxidant (SC50) activity of Euphorbia tirucalli stem was in the range of 12.91 ± 0.70 and 528.33 ± 25.15 μg/mL. At concentrations of 5.0 and 7.5 mg/mL, the diameter of inhibition of the ethyl acetate fraction was 14.33 ± 0.76 mm and 17.87 ± 0.57 mm, respectively. The MIC (minimum inhibitory concentration) was 0.156 mg/mL. Scopoletin, gallic acid, and piperic acid got MICs corresponding to 78, 312, and 312 μg/mL, respectively. Scopoletin, gallic acid, and piperic acid were found in the ethyl acetate fraction of Euphorbia tirucalli and exhibited the treatment of citrus bacteria canker and plant diseases.

Introduction: Phlorotannins are bioactive-value polymers existing in brown algae and useful for pharmaceutics and functional food. Therefore, the study focused on the spray drying conditions survey, the evaluation of antioxidant activities, and physico-chemical characterization of antioxidant nano phlorotannin powder prepared from brown algae Sargassum serratum. Methods: To survey the effect of spray drying conditions (carriers, carrier-to-solution ratio, compressed air pressure, liquid feed speed, inlet air temperature) on antioxidant activities (total antioxidant, reducing power, DPPH free radical scavenging), and physico-chemical (solubility degree, moisture, particle morphology, and bulk density) of antioxidant phlorotannin powder from brown algae Sargassum serratum commonly growing in the Vietnam sea area. Results: The optimum spray drying condition consisted of the carrier-to-solution ratio of 10%, compressed air pressure of 0.8 bar, the liquid feed speed of 10 ml min-1, and the inlet temperature of 110°C. At the optimization condition, the antioxidant activity of phlorotannin powder possessed total antioxidant (4.347 ± 0.018 g ascorbic acid equivalent 100-1 g DP), reducing power activity (9.390 ± 0.024 g FeSO4 equivalent 100-1 g DP), DPPH free radical scavenging activity ((70.02 ± 0.26)%), physico-chemical of antioxidant phlorotannin powder consisting of moisture content (5 ± 0.5%), phlorotannin content (2.268 ± 0.010 g phloroglucinol equivalent 100-1 g DP), solubility degree (100%), and bulk density (<1 g/ml). Phlorotannin content and antioxidant activities were affected by the spray drying condition (p < 0.05) and a strong correlation to each other (R2 > 0.9). Antioxidant phlorotannin particles possessed nanometer size and the morphology of irregular and microspheres. Conclusion: Antioxidant nano phlorotannin powder could be usefulas functional food and pharmaceuticals.