Onion contains many dietary and bioactive components including phenolics and
flavonoids.
Spiraeoside (quercetin-4-O-β-D-glucoside) is one of the most putative
flavonoids in onion. Several
antioxidant techniques were used in this investigation to assess the
antioxidant capabilities of
spiraeoside, including
1,1-diphenyl-2-picrylhydrazyl radical (DPPH·) scavenging,
N,N-dimethyl-p-phenylenediamine radical (DMPD•+) scavenging, 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulphonate) radical (ABTS•+) scavenging activities, cupric
ions (Cu2+) reducing and
potassium ferric
cyanide reduction abilities. In contrast, the water-soluble α-
tocopherol analogue
trolox and the conventional
antioxidants butylated hydroxytoluene (
BHT),
butylated hydroxyanisole (
BHA), and α-
tocopherol were utilized as the standards for evaluation.
Spiraeoside scavenged the DPPH radicals an IC50 of 28.51 μg/mL (r2: 0.9705) meanwhile
BHA,
BHT,
trolox, and α-
tocopherol displayed IC50 of 10.10 μg/mL (r2: 0.9015), 25.95 μg/mL (r2: 0.9221), 7.059 μg/mL (r2: 0.9614) and 11.31 μg/mL (r2: 0.9642), accordingly. The results exhibited that
spiraeoside had effects similar to
BHT, but less potent than α-
tocopherol,
trolox and
BHA. Also, inhibitory effects of
spiraeoside were evaluated toward some metabolic
enzymes including
acetylcholinesterase (AChE),
butyrylcholinesterase (BChE),
carbonic anhydrase II (CA II) and α-
glycosidase, which are related to a number of illnesses, such as
Alzheimer's disease (AD),
diabetes mellitus and
glaucoma disorder.
Spiraeoside exhibited IC50 values of 4.44 nM (r2: 0.9610), 7.88 nM (r2: 0.9784), 19.42 nM (r2: 0.9673) and 29.17 mM (r2: 0.9209), respectively against these
enzymes.
Enzyme inhibition abilities were compared to clinical used inhibitors including
acetazolamide (for CA II),
tacrine (for AChE and BChE) and
acarbose (for α-
glycosidase).
Spiraeoside demonstrated effective
antioxidant,
anticholinergic,
antidiabetic and antiglaucoma activities. With these properties, it has shown that
Spiraeoside has the potential to be a medicine for some
metabolic diseases.