Comparative Analysis Of In Vitro Bioactivities And Phenolic Content Of Leaf Extracts From Six Species Of Aquilaria
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Date
2016-09
Authors
Ibrahim, Azlinda
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Abstract
This study was carried out to compare the in vitro antioxidant, antibacterial,
anti-diabetic and anti-inflammatory properties of the leaf extracts of six species from
genus Aquilaria which are; Aquilaria beccariana, Aquilaria hirta, Aquilaria
malaccensis, Aquilaria rostrata, Aquilaria sinensis and Aquilaria subintegra. Their
phenolic compounds were also identified and quantified. From the preliminary
screening using five fresh extracts (ethyl acetate, acetone, ethanol, methanol and
distilled water) from each species, the methanolic extracts exhibited the best
antioxidant activities. This solvent was then selected for further extraction and half
of the extracts were also hydrolyzed. A. sinensis recorded the highest percentage of
2,2-diphenyl-1-picrylhydrazyl (DPPH) activity (hydrolyzed extract; 94.33±4.89%)
and ferric-reducing antioxidant power (FRAP) activity (methanolic extract and
hydrolyzed extract; 96.00±0.55% and 95.88±0.16%), and the methanolic extract of
A. hirta gave the highest percentage of metal chelating activity (90.05±3.47%). Only
gastrointestinal bacteria were selected for antibacterial study. The hydrolyzed extract
of A. hirta performed better activity with minimum inhibitory concentration (MIC)
values ranging from 250 to 500 μg/mL. In the α-glucosidase inhibition test, the 2.5
mg/mL hydrolyzed extract of A. sinensis exhibited the highest percentage of
inhibition at 59.00±8.07%. In α-amylase inhibition test, the highest inhibitory
activity was only 23.35±1.30% detected from the 10 mg/mL hydrolyzed extract of A.
hirta. The highest cyclooxygenase inhibitory activity was only 25.89±2.59% for the
methanolic extract of A. subintegra. This extract also has the highest total phenolic
content (127.80±2.57 μg GAE/mg extract). From the quantitative analysis using ultra
performance liquid chromatography (UPLC), major content of mangiferin was
quantified from the methanol extracts of A. hirta, A. malaccensis, A. sinensis and A.
subintegra and the hydrolyzed extract of A. hirta. Iriflophenone 2-O-α-rhamnoside
was found to be the major compound of A. rostrata and iriflophenone 3-C-β-
glucoside is the major compound in A. beccariana. 7,4'-di-O-methylapigenin was the
major compound of the hydrolyzed extracts of A. beccariana, A. malaccensis, A.
rostrata and A. subintegra, while 7,3'-di-O-methylluteolin is the major compound in
the hydrolyzed extract of A. sinensis.
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Keywords
Compare the in vitro antioxidant, antibacterial, anti-diabetic and anti-inflammatory properties , of the leaf extracts of six species from genus Aquilaria