In vitro anti-inflammatory and anti-oxidant activities of Sri Lankan medicinal plants

The search for novel sources of new anti-inflammatory agents has gained an increasing demand with the rising number of indications of inflammatory mediated diseases. Traditionally, medicinal plant extracts have been used to treat number of diseases mediated by inflammation and still remain as potent sources of new anti-inflammatory agents and antioxidants. Therefore, the present study was undertaken to evaluate the in vitro anti-inflammatory and anti-oxidant properties of ten Sri Lankan medicinal plant extracts, traditionally used to treat diseases associated with inflammation.Arachidonate-5-lipoxygenase (A5-LOX), hyaluronidase, xanthine oxidase enzyme inhibitory assays and nitric oxide (NO) production inhibitory assay in lipopolysaccharide activated RAW 264.7 macrophages were used to evaluate in vitro anti-inflammatory activity. Antioxidant activity, total polyphenolic and total flavonoid contents were determined using six standard in vitro assays.The extract of Murraya koenigii L.exhibited the highest anti-A5-LOX activity (IC50=7.83±0.42μg/mL), while that of Symplocos cochinchinesis Lour. showed high anti-hyaluronidase activity (69.35%) along with a high oxygen radical absorbance capacity (ORAC) (1539±31mg TE/g). The extract of Calophyllum innophyllum L. also exhibited high anti-hyaluronidase activity (68.45% at 500μg/mL), xanthine oxidase inhibitory activity (60.63% at 250μg/mL), NO production inhibitory activity (35.00% at 500μg/mL) along with a marked 2,2-diphenyl-2-picryl-hydrazyl (DPPH) free radical scavenging activity (IC50=4.42±0.03μg/mL) and ferric reducing antioxidant power (FRAP) (8231±5mg TE/g). Ferrous ion chelating (FIC) activity of plant extracts was found to be low in comparison with the reference standard EDTA-Na2. Higher total polyphenol content (TPC) and total flavonoid content (TFC) were recorded for the extracts of Cyanometra cauliflora L. and Murraya koenigii L. respectively. All bio-activities were found to be significant at p<0.05. In the correlations analysis, a high positive correlation was observed between anti-A5-LOX and DPPH free radical scavenging activities. Moderate, positive correlations were observed among NO production inhibitory, xanthine oxidase inhibitory activities, FRAP and ORAC of plant extracts.This is the first report demonstrating the anti-A5-LOX, anti-hyaluronidase, xanthine oxidase and nitric oxide production inhibitory activities of ethanol extracts of the tested Sri Lankan medicinal plant extracts. The findings of the study support the traditional uses of these plant extracts against inflammatory mediated diseases. Moreover, the extracts, having promising in vitro anti-inflammatory and antioxidant properties could be effectively used for pharmaceutical, neutraceutical as well as for cosmaceutical applications.