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Oxygen radical antioxidant capacity (ORAC) and antibacterial properties of Melicope glabra bark extracts and isolated compounds


Quek, Alexandra and Mohd Zaini, Hafizah and Kassim, Nur Kartinee and Sulaiman, Fadzil and Rukayadi, Yaya and Ismail, Amin and Zainal Abidin, Zamirah and Awang, Khalijah (2021) Oxygen radical antioxidant capacity (ORAC) and antibacterial properties of Melicope glabra bark extracts and isolated compounds. PLoS One, 16 (5). art. no. e0251534. pp. 1-12. ISSN 1932-6203


Melicope glabra (Blume) T. G. Hartley from the Rutaceae family is one of the richest sources of plant secondary metabolites, including coumarins and flavanoids. This study investigates the free radical scavenging and antibacterial activities of M. glabra and its isolated compounds. M. glabra ethyl acetate and methanol extracts were prepared using the cold maceration technique. The isolation of compounds was performed with column chromatography. The free radical scavenging activity of the extracts and isolated compounds were evaluated based on their oxygen radical absorbance capacity (ORAC) activities. The extracts and compounds were also subjected to antibacterial evaluation using bio-autographic and minimal inhibitory concentration (MIC) techniques against two oral pathogens, Enterococcus faecalis and Streptococcus mutans. Isolation of phytoconstituents from ethyl acetate extract successfully yielded quercetin 3, 5, 3’-trimethyl ether (1) and kumatakenin (2), while the isolation of the methanol extract resulted in scoparone (3), 6, 7, 8-trimethoxycoumarin (4), marmesin (5), glabranin (6), umbelliferone (7), scopoletin (8), and sesamin (9). The study is the first to isolate compound (1) from Rutaceae plants, and also the first to report the isolation of compounds (2–5) from M. glabra. The ORAC evaluation showed that the methanol extract is stronger than the ethyl acetate extract, while umbelliferone (7) exhibited the highest ORAC value of 24 965 μmolTE/g followed by glabranin (6), sesamin (9) and scopoletin (8). Ethyl acetate extract showed stronger antibacterial activity towards E. faecalis and S. mutans than the methanol extract with MIC values of 4166.7 ± 1443.4 μg/ml and 8303.3 ± 360.8 μg/ml respectively. Ethyl acetate extract inhibited E. faecalis growth, as shown by the lowest optical density value of 0.046 at a concentration of 5.0 mg/mL with a percentage inhibition of 95%. Among the isolated compounds tested, umbelliferone (7) and sesamin (9) exhibited promising antibacterial activity against S. mutans with both exhibiting MIC values of 208.3 ± 90.6 μg/ml. Findings from this study suggests M. glabra as a natural source of potent antioxidant and antibacterial agents.

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Additional Metadata

Item Type: Article
Divisions: Faculty of Medicine and Health Science
Faculty of Science
Institute of Bioscience
DOI Number: https://doi.org/10.1371/journal.pone.0251534
Publisher: Public Library of Science
Keywords: Oxygen radical antioxidant capacity (ORAC); Antibacterial, Melicope glabra
Depositing User: Mas Norain Hashim
Date Deposited: 29 Nov 2022 03:52
Last Modified: 29 Nov 2022 03:52
Altmetrics: http://www.altmetric.com/details.php?domain=psasir.upm.edu.my&doi=10.1371/journal.pone.0251534
URI: http://psasir.upm.edu.my/id/eprint/94492
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