Schinus terebinthifolia Raddi is widely used in traditional Brazilian medicine to treat respiratory diseases, as an antiseptic, anti-inflammatory, and hemostatic agent. This study aimed to evaluate the influence of climatic parameters on the yield, antioxidative capacity, and chemical composition of the S. terebinthifolia leaf essential oil. The specimen was collected monthly from October 2021 to September 2022. Leaf essential oils (EOs) were obtained by hydrodistillation, and their chemical compositions were analyzed by gas chromatography/mass spectrometry (GC/MS). Statistical analyses were performed to verify the climatic influences on the yields, chemical composition, and antioxidative capacity. The DPPH (2,2-diphenyl-1-picrylhydrazyl) radical-scavenging and inhibition of β-carotene/linoleic acid oxidation assays were performed to assess the antioxidant activity. The leaf essential oil yields ranged from 0.1% (July) to 0.7% (May and September), averaging 0.5 ± 0.2%. There was no significant difference in essential oil production during the dry (0.4 ± 0.2%) and rainy (0.6 ± 0.1%) seasons. The main chemical constituents identified in essential oils were limonene (11.42–56.24%), δ-3-carene (8.70–33.16%) and (E)-caryophyllene (4.10–24.98%). The limonene annual average was 43.57 ± 12.74% and showed no statistical difference during the dry (40.53 ± 13.38%) and rainy (52.68 ± 3.27%) seasons. Likewise, the annual average of δ-3-carene was 22.55 ± 7.11%, displaying no statistical difference between dry (26.35 ± 7.90%) and rainy (31.14 ± 1.63%) seasons. The annual average of (E)-caryophyllene was 11.07 ± 7.15% and this constituent did not show a statistical difference in Tukey’s test (p > 0.05) during the dry (12.72 ± 7.56%) and rainy (6.10 ± 1.78%) season. Limonene showed a moderate positive and significant correlation (p < 0.05) with precipitation (r = 0.56) and a weak correlation with temperature (r = −0.40), humidity (r = 0.40), and insolation (r = −0.44). All samples inhibited the oxidation in the β-carotene/linoleic acid system (22.78–44.15%) but displayed no activity in the DPPH method.

Hyptis crenata (Pohl) ex Benth is used in traditional medicine as an analgesic to treat general pain. Six Hyptis crenata samples (Hc-1 to Hc-6) were collected in Pará state, Brazil. The leaf essential oils were obtained by hydrodistillation, and GC-MS and GC-FID were used to analyze their chemical compositions. The antioxidant capacity was measured in vitro using DPPH and carotene/linoleic acid assays. Chemometrics analysis (PCA, HCA, and clustered heat map) were used to identify the sample relationships between those collected in this study and those from the literature (Hc-7 to Hc-16) samples. According to the main chemical constituents identified in the samples described in this work and the literature, the sixteen samples were classified into ten groups. Group I was characterized by 1,8-cineole (31.0%), α-pinene (13.6%), (E)-caryophyllene (7.8%), and β-pinene (7.6%); and Group IV was characterized by 1,8-cineole (17.4–23.5%), α-pinene (15.7–23.5%), β-pinene (10.5–13.4%), and limonene (8.5–9.7%). Both groups are described for the first time. The total antioxidant capacity was expressed in Trolox Equivalent Antioxidant Capacity values (TEAC): TEAC of Hc-5 (551.9 mg.TE/g) and Hc-6 (475.1 mg.TE/g). In the β-carotene/linoleic acid assay, the highest inhibition was from Hc-2 (40.0%), Hc-6 (39.0%), and Hc-3 (29.4%).

Aniba canelilla (Kunth) Mez essential oil has many biological activities due to its main compound 1-nitro-2-phenylethane (1N2F), followed by methyleugenol, a carcinogenic agent. This study analyzed the influence of seasonality on yields, antioxidant capacity, and 1N2F content of A. canelilla leaf and twig essential oils. Essential oils (EOs) were extracted with hydrodistillation and analyzed with gas chromatography coupled to mass spectrometry and a flame ionization detector. Antioxidant capacity was measured using the free radical scavenging method (DPPH). Chemometric analyses were carried out to verify the influence of climatic factors on the production and composition of EOs. 1-Nitro-2-phenylethane was the major constituent in A. canelilla EOs throughout the seasonal period (68.0–89.9%); methyleugenol was not detected. Essential oil yields and the 1N2F average did not show a statistically significant difference between the dry and rainy seasons in leaves and twigs. Moderate and significant correlations between major compounds and climate factor were observed. The twig oils (36.0 ± 5.9%) a showed greater antioxidant capacity than the leaf oils (20.4 ± 5.0%). The PCA and HCA analyses showed no statistical differences between the oil samples from the dry and rainy seasons. The absence of methyleugenolin in all months of study, described for the first time, makes this specimen a reliable source of 1N2F.