Myrmecodia, or ant nest plant, is an indigenous medicinal plant traditionally used by local people in West Papua to treat a variety of hereditary diseases. It has been empirically proven to have a positive effect in treating various types of cancer, diabetes, heart problems, hypertension, lung, stroke, etc. High performance thin layer chromatographic (HPTLC) methods were developed and validated in order to compare antioxidant activity and to evaluate the contribution of selected phenolic compounds and stigmasterol to total antioxidant capacity in different extracts from Myrmecodia platytyrea. As expected, total phenolic content is highly correlated with antioxidant activity (R=0.86). The ethyl acetate extract had the highest reducing antioxidant activity, followed by ethanol, methanol and dichloromethane. The phenolic content of extracts was observed to increase in the following order: methanol>ethyl acetate>ethanol>dichloromethane. Although, the highest solubility of sterols observed in the ethyl acetate extract, might contribute to the highest antioxidant activity observed in this extract, there was no significant antioxidant activity of stigmasterol observed. While polyphenolic content is highly correlated to gallic acid concentration, free radical scavenging activity is related to caffeic acid. Strong positive and significant correlations between total phenolic content and radical scavenging activity, suggests that phenolic compounds are the main contributors to antioxidant activity in the sample extracts. Although the ethyl acetate extract has significant antioxidant activity, its' antioxidant activity was found not to be related to the plant sterols present in the extract.