Muhammad Hassnain Haideri. Antioxidant and antbacterial activity of extracts from the leaves of Gymnema inodorum. Master's Degree(Health Sciences Research). Chiang Mai University. Library. : Chiang Mai University, 2024.
Antioxidant and antbacterial activity of extracts from the leaves of Gymnema inodorum
Abstract:
In recent years, there has been an increasing concern surrounding the utilization
of plant extracts for their possible antimicrobial properties, given the worldwide health
and development concerns surrounding the rise of antimicrobial resistance. The use of
plant extracts as natural remedies for various ailments has been a traditional practice for
centuries. Gymnema inodorum, a medicinal herb locally known as Chiang-da found in
tropical regions including Northern Thailand, has a wide range of therapeutic uses. The
study aims to investigate the antioxidant and antimicrobial activity of Gymnema inodorum from Northern Thailand using different solvent extracts obtained through
various extraction methods.
Employing maceration, decoction, microwave-assisted extraction (MAE),
Soxhlet reflux extraction and fractionation of crude extract, impact on bioactive profile
of Gymnema inodorum leaves extract, specifically focusing on antimicrobial activity,
antioxidant activity, gymnemic acid levels, and phenolic content was studied. Our results
demonstrated that the extract has no or little antimicrobial activity against Staphylococcus
aureus, Staphylococcus epidermidis, Escherichia coli, and Salmonella enterica. Soxhlet
Reflux consistently yielded the highest antioxidant activity, ranging from 50.29 0.00 to
61.94 ± 0.01 mg TE/g, highlighting its efficacy in extracting potent antioxidants from
Gymnema inodorum.
Gymnemic acid levels were significantly affected by the extraction method, with
reflux producing the highest concentrations (8.24 ± 0.65 mg) per gram of extract.
Phenolic content, crucial for overall bioactivity, was also maxinized by retlux, with
values reaching 82.54 ± 0.07 mg GAE g-1.
The ethanol-reflux extracts of G. inodorum leaves were subjected to columm
chromatography for the isolation of phenolic compounds and maximize antioxidant and
phenolic activity. Total phenolic and flavonoid contents of fractionated extract were
assessed using Folin-Ciocalteu and aluminium chloride colorimetric methods,
respectively. Total antioxidant activity was evaluated by employing different antioxidant
assays, including 2,2-dipheny1-1-picrylhydrazyl (DPPH), 2.2'-azino-bis-(3-ethylbenzo
thiazoline-6-sulfonic) acid (ABTS) scavenging assay and ferric reducing antioxidant
power (FRAP) assay. High-Performance Liquid Chromatography (HPLC) with a C18
column was employed to determine the level of gynnenic acid, while Liquid
Chromatography Quadrupole Time-of-Flight'Mass Spectrometry (LC-QTOFMS) was
used to identify potential phenolic compounds.
The three separated fractions indicating A, B. and C, exhibited remarkable
antioxidant activity, with total phenolic content of 0.294 ± 0.056, 0.085 ± 0.039, and
0.227 ± 0.041 mg QE/g, and total Havonoid content of 0.274 ± 0.050, 0.309 ± 0.110, and
0.384 ± 0.007 mg QE/g, respectively. Fraction A exhibited the highest DPPPH and ABTS
scavenging activity, while fraction C demonstrated significantly higher ferric-reducing
power. HPLC analysis revealed the highest concentration of gymnemic acid in fraction C
(3.93 ± 0.004 mg/g) compared to fraction A (1.41 ± 0.000 mg/g) and fraction B (1.59 ±
0.004 mg/g). The LC-QTOF/MS phenolic screening showed seven potential phenolic
compounds in fraction A. seven compounds in fraction B. and four compounds in Fraction
C. A significant relationship is found between antioxidant potential and total phenolic
content, suggesting that phenolic compounds are the major contributors to the antioxidant
activity of G. inodorum.
This study underscores the pivotal role of extraction methods in influencing the
antioxidant potential, gymnemic acid levels, and phenolic content in Gymnema inodorum
leaves extract.