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Objective: To assess the antioxidant activity as well as the total polyphenolics and flavonoids content of thirteen extracts from nine wild orchids of Nepal. Methods: First, a preliminary phytochemical screening of thirteen extracts of nine orchids was carried out using established protocols. Then, the total polyphenolic and flavonoid contents of each extract were evaluated using the Folin-Ciocalteu's phenol reagent and aluminium chloride methods respectively. Finally, antioxidant activity was determined by 2, 2-diphenyl-1-picryl hydrazyl free radical scavenging assay and expressed in terms of half inhibition concentrations (IC50 values).

Results: All the tested parameters showed significant variation at P= 0.05. The total flavonoids varied with the greatest amounts found in the leaves of Rhynchostylis retusa and the smallest amounts found in the roots of Gastrochilus acutifolius (G. acutifolius). The amount of total polyphenolics was highest in the stems of Vanda cristata and lowest in the leaves of G. acutifolius. Antioxidant activity was highest in the stems of Vanda cristata and lowest in the leaves of G. acutifolius.

Conclusions: Some of the orchid extracts studied exhibited levels of antioxidant activity which were comparable to or even higher than those found for extracts of medicinal plants and orchids studied previously. It is suggested that drugs and natural food additives can be extracted from those wild orchids with high levels of antioxidant activity.