This paper reports the first chemical study of the non-volatile compounds, antioxidant capacity and antimicrobial effect of the methanol extract of the leaves of McVaugh. Samples of the leaves were collected in Maracanã Municipality, Pará, Brazil. The chemical investigation led to the identification of the triterpenoids β- and α-amyrin, the flavonoids 4'--galloyldihydromyricetin, myricetin, myricitrin, desmantin-I, myricetin-3--(3"--galloyl)-α-L-rhamnopyranoside and isovitexin, in addition to gallic acid. The methanol extract showed antioxidant capacity (>90%) against DPPH radical (IC 356.3 ± 3.1 μg.mL) and was active only at high concentrations against the tested microorganisms, including the chloramphenicol resistant CCMB261 and CCMB285 and a nystatin resistant CCMB 288. This study shows that like other species, is another source of flavonoids such as desmantin-I and myricitrin which have shown hypoglycemic potential, besides triterpenes and phenolic acids.