Abstract:
The inhibitors of Arachidonate 5-Lipoxygenase (A5-LOX) and hyaluronidase enzymes have
gained a high therapeutic value in the treatment of inflammatory diseases. Medicinal plants
remain as potent sources of new enzyme inhibitors and antioxidants. Argyreiapopulifolia
(Convolvulaceae) is a common medicinal plant, endemic to Sri Lanka, used for the
treatment of various diseases including inflammatory diseases in the Sri Lankan folklore.
The objective of the present study is to investigate in vitro anti-A5-LOX, anti-hyaluronidase
and anti-oxidant properties of ethanol leaf extract of A. populifolia. The air-dried, powdered
leaf of A. populifolia was extracted with ethanol using cold extraction technique. In vitro
anti-inflammatory activity was determined by A5-LOX and hyaluronidase enzyme inhibitory
assays. Anti-oxidant activity was determined by DPPH free radical scavenging, Ferric
Reducing Anti-oxidant Power (FRAP), Ferrous Iron Chelating (FIC) and Oxygen Radical
Absorbance Capacity (ORAC) assays. The Total Phenolic Content (TPC) and Total
Flavonoid Content (TFC) were also determined. The ethanol leaf extract of A. populifolia
showed a moderate anti-A5-LOX activity, having the IC50 value of 150.8 ± 1.5μg/mL in
comparison to Baicalein (1.55 ± 0.24 μg/mL) and exhibited hyaluronidase enzyme inhibition
of 16.3 ± 0.7% at 500 μg/mL in comparison to Tannic acid (90.3 ± 0.8% of inhibition at 500
μg/mL). The extract exhibited moderate DPPH free radical scavenging activity (IC50=291.6
± 5.4 μg/mL, Trolox: 5.29 ± 0.09 μg/mL) and ORAC (476.2 ± 31.8 mg TE/g), in comparison
to that of green tea extract (1662.82 ± 0.22 mg TE/g). The extract showed low FRAP (265.1
± 2.2 mg TE/g) with no FIC activity. The TPC and TFC were found to be 10.59 ± 1.16 mg
Gallic Acid Equivalents (GAE)/g and 21.79 ± 0.39 mg Quercetin Equivalents (QE)/g
respectively. The anti-A5-LOX, anti-hyaluronidase and anti-oxidant activities of leaf extract
of A. populifoliawere significantly different from the respective reference standards
(P<0.05). This is the first report of A5-LOX and hyaluronidase related anti-inflammatory
activities and anti-oxidant activities of ethanol leaf extract of A. populifolia in vitro. The
present study may provide impetus to search for novel anti-inflammatory compounds from
this plant and supports the traditional claims.
