Abstract:
Seaweeds are an important source of bioactive metabolites in drug development and
nutraceuticals. Therefore, present study aimed to investigate in-vitro antidiabetic activities of
methanol extract and its solvent fractions of Sri Lankan marine red algae, Gracillaria edulis
(Gmelin) Silva (Family: Gracilariaceae). De-polysaccharide methanolic extract of G. edulis was
partitioned with hexane, chloroform and ethyl acetate respectively. In-vitro antidiabetic activity
was evaluated in crude methanol extract, hexane, chloroform (CH), ethyl acetate (EA) and
aqueous (AQ) fractions of G. edulis. The α-amylase inhibitory activity was determined using the
3, 5 dinitrosalicylic acid method and anti-glycation activity was performed using glucoseinduced
protein glycation and formation of protein-bound fluorescent advanced glycation end
products (AGEs). The highest alpha amylase inhibitory activity was reported in methanol extract
with IC50 value of 170.45±1.17 μg/ml and the % inhibition varied from 54.13% (200 μg/ml) to
16.26% (6.25 μg/ml). The IC50 values of amylase inhibitory activities of hexane, CH, EA and
AQ fractions of G. edulis were 393.04±4.73 μg/ml, 322.71±4.80 μg/ml, 279.48±5.62 μg/ml and
376.49±12.14 μg/ml respectively. Results showed a significant (p<0.05) difference of IC50
values between methanol extraction, chloroform and ethyl acetate fractions. The highest antiglycation
activity was reported in CH fraction of G. edulis with IC50 value of 258.23±3.24 μg/ml
compared to methanol extract (IC50:702.33±12.72 μg/ml). The % inhibition of CH fraction varied
from 83.88% (800 μg/ml) to 13.84% (25 μg/ml). The IC50 values of anti-glycation activity of
hexane, EA and AQ fractions were 637.53±6.21 μg/ml, 586.54±4.37 μg/ml and 723.78±12.81
μg/ml respectively. Results showed a significant difference of IC50 values of hexane, chloroform
and ethyl acetate fractions (p<0.05). In conclusion, methanol extraction of G. edulis and its
fractions showed alpha amylase and anti glycation activity with varying degrees of potentials.
Among them methanol extract showed comparatively high alpha amylase inhibition while
chloroform fraction showed high capability of preventing the formation of AGE products.
Hence, isolation of active compounds from methanol extract and chloroform fraction is
warranted.
