| الملخص: | Aquilaria sinensis is commonly known as Gaharu belongs to the family of
Thymelaeceae. It has been used as traditional medicine for diabetes treatment and
possesses several other pharmacological activities. The objective of the present study is
to determine the antioxidant and anti hyperglycaemic properties in the A. sinensis
leaves. The methanolic leaves extract of A. sinensis was fractionated via solvent –
solvent extraction using n-hexane, dichloromethane, butanol, chloroform, ethyl acetate
and methanol aqueous to produce fractions. The TLC results of the plant extracts
showed the presence of phenolic, terpenoid and alkaloid compounds. The total phenolic
contents is the highest in the ethyl acetate extract at 1.69 ± 0.02 mg GAE/ g dry weight
and the total flavonoid content highest in butanol fraction extract at 3.59 ± 0.07 mg QE
/ g dry weight. The fractions were subjected to the in vitro antioxidant assay. The results
showed that ethyl acetate fraction exhibited the higher scavenging DPPH radicals
activity with IC50 value of 0.10 ± 0.02 mg/ml, the highest ability of ferric reducing
power activity at 0.37 ± 0.07 mmol/g extract , and good chelating of metal with IC50 <
0.05 ±0.01 mg/ml. However, methanol aqueous exhibits the highest scavenging of
superoxide radical activity with IC50 value of 0.18 ± 0.01 mg/ml, nitric oxide radical
scavenging activity with IC 50 >1.6 ± 0.001 mg/ml. Based on the results obtained from
the antioxidant assays, the fractions which showed good antioxidant activities were
subjected to in vitro anti hyperglycaemic assay. Among all of the active fractions, ethyl
acetate showed the highest inhibition of alpha amylase enzyme at 43.14% with IC50
value of >1.6 ± 0.04 mg/ml, inhibition of alpha glucosidase enzyme at 81.06% with
IC50 value of < 1.6 ± 0.03 mg/ml, inhibition of glycogen phosphorylase at 17 % with IC50 value of >1.6 ± 0.09 mg/ml and inhibition of haemoglobin glycosylation at 65.25 %
with IC50 value of 0.87 ± 0.12 after 72 hours of incubation. However, all of the fractions
showed poor inhibition on glycogen phosphorylase enzyme activity. The results from
the LCMS analysis showed the presence of a bioactive compound, magniferin in
aqueous fraction and tripteroside in ethyl acetate fraction. Those compounds are
actively known to have the properties of anti hyperglycaemic and antioxidant. In
conclusion, the leaves of the A. sinensis possessed antioxidant and anti hyperglycaemic
activity that provide scientific evidence to support the claim of traditional medicinal or
herbal medicinal in treating diabetes.
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