1. Full name: Lê Huy Hoàng                                                       2. Sex: Male

3. Date of birth: 16/08/1981                                                       4. Place of birth: Bac Giang

5. Admission decision number: Decision No. 4860/QĐ-ĐHKHTN, dated on 24 November, 2014 by Rector of VNU University of Science

6. Changes in academic process: Decision No. 3548/QĐ-ĐHKHTN date on 18/10/2017 and Decision No. 4728/QĐ-ĐHKHTN date on 28/12/2018

7. Official thesis title: Research of an extraction process for obtaining a standardized extract of quercetin from some medicinal plants and their biological activity.

8. Major: Biochemistry                                                               9. Code: 9420101.16

10. Supervisors: Assoc. Prof. Dr. Nguyen Quang Huy

Assoc. Prof. Dr. Ho Ba Do

11. Summary of the new findings of the thesis

            - The thesis has been established an HPLC method to simultaneously separate and detect quercetin compound in plant extracts with the highest efficiency. The separation was performed on a ZORBAX SB-C18 column which operated at 25 degrees C with the isocratic elution by using methanol/acetonitrile/H2O (15/65/20, v/v/v) as mobile phase at a flow rate of 1.0 mL/min and detection by DAD at 370 nm. The total run time was 7 minutes. The method meet the requirements of the accuracy as well as system suitability in HPLC analysis according to the ICH guidelines.

            - The thesis has been shown for the first time in Vietnam that the standardized extract of quercetin which had different purity were obtained from the flower buds of Sophora japonica L or leaf of Nelumbo nucifera Gaertn. According to the process for obtaining a standardized extract of quercetin, the semi-purified extract, that was denoted either by H1 (from the flower buds of Sophora japonica L) or by S (from the leaf of Nelumbo nucifera Gaertn), as well as the purified extract that was denoted by H2 (from rutin that was isolated from the flower buds of Sophora japonica L) was obtained. This research has been determined that quercetin was found in all extracts the contents (%, weight) being highest in samples H2 (90.02%), H1 (59.19%), and S (10.85%).

            - The thesis has been shown that the new data about biological activity in vitro and in vivo of both the semi-purified extract (H1) and the purified extract (H2) from the flower buds of Sophora japonica L. The H1 or H2 sample presented considerable biological properties including in vitro antioxidant activity by % DPPH free radical scavenging activity showing an IC50 value of 413,62 or 16,35 µg/ml and anticancer activity evaluated by cytotoxicity assay against HCT116 colorectal cancer cell line with an IC50 value of 18,79 or 19,53 µg/ml. In vivo, the H1 and H2 samples (at doses of 20 mg/kg) were non-toxic; improved antioxidant ability and protected liver mice in a normal state or in conditions of heat shock. Their samples had an antioxidant activity as well as protected liver mice from being poisoned by the paracetamol drug.

12. Practical applicability, if any:

            These results contribute oriented method of obtaining the standardized extract of quercetin from the medicinal plants in order to promote the application of bioactive quercetin in nutritional therapy to ameliorate oxidative stress which related to age, living conditions, occupations or drug toxicity during treatment.

13. Further research directions, if any:

- Future research is required to evaluate the semi-purified extract (H1) for its effect on strength, stamina, and fatigue which related to paracetamol drug or heat stress based on the signaling molecules such as cytokines, heat shock proteins, hormones cortisol.

- Further research is needed the extraction of a larger mass of the flower buds of Sophora japonica L) or the leaf of Nelumbo nucifera Gaertn. This study for obtaining the standardized extract of quercetin (H1, S) in order to standardize compounds which is beneficial ingredients but not quercetin.

14. Thesis-related publications:

            [1]. Do Thi Hai Anh, Le Huy Hoang, Kitsamone Shihavong, Nguyen Thai Uy, Nguyen Quang Huy (2016), “In vitro antibacterial activity of Quercetin containing extract from Hibiscus sabdariffa L. calyxes”, VNU Journal of Science: Natural Sciences and Technology  32 (1S), 147-152.

            [2] Le Huy Hoang, Do Thi Hai Anh, Do Thi Hue, Tran Thi Kieu Oanh, Nguyen Quang Huy (2016), “Determination of quercetin qglycone in flos Sophorae japonicae extract by high performance liquid chromatography”, VNU Journal of Science: Natural Sciences and Technology 33 (1S), 214-223.

            [3] Le Huy Hoang, Pham Thi Phuong, Nguyen Thi Hanh, Ho Ba Do, Nguyen Quang Huy (2019), “Study of ultrasound-assisted acid hydrolysis to obtain

quercetin and their antioxidant activities from some plants”, VNU Journal of Science: Natural Sciences and Technology 35 (4), 88-95.

            [4] Le Huy Hoang, Pham Thi Phuong, Bui Thi Van Khanh, Ho Ba Do, Nguyen Quang Huy (2019), “Biological evaluation of the standardized quercetin

extracts from the flos sopharae immaturus (of Sophora japonica L.) and the lotus leaves (of Nelumbo nucifera Gaertn.,), Pharmaceutical Journal  519, 55-58.