2.1. Reagents and Chemical Analogues

MCEO was acquired from Hebron company® (Recife, Brazil). Monoterpenoid ROT was isolated from MCEO as earlier described by Almeida and collaborators [19]. MCEO analysis by GC/MS found rotundifolone in 58.11% [16]. This essential oil was submitted to preparative thin-layer chromatography (PTLC) on silica gel and developed with hexane. Plates were exposed under UV light (254 nm), and ROT was visualized as the major component. Afterwards, ROT was removed from chromatographic plates, extracted with CH2Cl2, filtered, and concentrated to give a yellowish oil. Structural characterization of ROT was carried out by infrared, 1H and 13C nuclear magnetic resonance (NMR) analysis, and comparison with literature data [16]. Compound (−)-perillyl alcohol (PALC) (purity 96%, GC) was purchased from Sigma-Aldrich (St. Louis, MO, USA). (+)-Hydroxycarvone [(+)-HCAR], (−)-hydroxycarvone [(−)-HCAR] [20], perillaldehyde (PALD) [21], perillaldehyde 1,2-epoxide (EPER1), and perillaldehyde 8,9-epoxide (EPER2) [22] were prepared according to literature and analyzed by infrared and 1H- and 13C-NMR. Chemical structures of evaluated compounds are shown in Figure 1.