Acerola cherry is a world famous fruit which contains abundant antioxidants such as vitamin C, anthocyanins, flavonoids, and phenolics. However, studies concerning bioactivity components from aerial parts of acerola (Malpighia emarginata) are scarce. In view of this, we have examined the constituents of aerial parts of acerola, and three new tetranorditerpenes acerolanins A–C (1–3) with a rare 2H-benz[e]inden-2-one substructure were isolated. Their structures were determined on the basis of spectral studies and acerolanin C was confirmed by X-ray crystallographic analysis. Furthermore, three new compounds have been studied for their cytotoxic activity.