Nineteen Thai medicinal plants used in Thai traditional medicine preparation to treat colds, asthma and fever were
studied for their antioxidant and NO inhibitory activities. Three extracts were obtained from each plant. First extract obtained
by macerating the plant part in 95% ethanol (Et) residue was boiled in water, where water extract (EW) was obtained. The
third extract (HW) was obtained by boiling each plant in water similar to that of Thai traditional medicine practice. These
extracts were tested for their antioxidant activity using DPPH assay, and anti-inflammatory activity by determination of
inhibitory activity on lipopolysaccharide (LPS) induced nitric oxide (NO) production in RAW 264.7 cell lines using Griess
reagent. Results indicated that Et, EW and HW of Syzygium aromaticum showed the highest antioxidant activity (EC50 = 6.56,
4.73 and 5.30 μg/ml, respectively). Et of Atractylodes lancea exhibited the most potent inhibitory activity on lipopolysaccharide
(LPS) induced nitric oxide (NO) production in RAW 264.7 cells, with IC50 value of 9.70 μg/ml, followed by Et of Angelica
sinensis and Cuminum cyminum (IC50 = 12.52 and 13.56 μg/ml, respectively) but water extract (EW, HW) of all plants were
apparently inactive. These results of anti-inflammatory activity of these plants correspond with the traditional use for fever,
cold, allergic-related diseases and inflammatory-related diseases.

Keywords: Antioxidant, RAW 264.7 cells, Nitric oxide, Lipopolysaccharide, Thai medicinal plants, Syzygium aromaticum,
Atractylodes lancea, Angelica sinensis, Cuminum cyminum