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Plectranthus amboinicus (Lour.) Spreng. also known as Indian borage or Mexican mint, is a perennial, succulent and strongly aromatic herb used in folk medicine for the treatment of respiratory diseases and digestive problems (Lukhoba et al., 2006). Characterized by its oregano-like odor and flavor, the species probably originated in Africa or India and it has since become widely distributed around the world for ornamental, medicinal and culinary purposes (Codd, 1975; Lorenzi and Matos, 2008; Arumugam et al., 2016). The therapeutic properties of P. amboinicus extracts are related to various biological activities, such as antimicrobial, antioxidant and antiinflammatory (da Costa et al., 2010; Swamy et al., 2017; Chiu et al., 2012). These properties are speculated to be ABSTRACT Plectranthus amboinicus, also known as Indian borage or Mexican mint, is a species of Lamiaceae cultivated worldwide for ornamental, culinary and medicinal purposes, being used in folk medicine for the treatment of respiratory diseases and digestive problems. These properties are attributed to the abundance of phenolic monoterpenes present in its essential oil, which have been extensively described in the literature. The low yield of essential oil hinders further investigation, besides the extraction being a costly and time-consuming procedure. The application of headspace-solid-phase microextraction (HS-SPME) coupled to gas chromatography-mass spectrometry (GC-MS), an alternative technique in plant volatile analysis, is described in the present study for P. amboinicus growing in Brazil. Four SPME fibers with different coating composition were evaluated: polydimethylsiloxane (PDMS -100 µm), carboxen/polydimethylsiloxane (CAR/PDMS -75 µm), divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS -50/30 µm) and polydimethylsiloxane/divinylbenzene (PDMS/DVB -65 µm). PDMS fiber extracted a total of 19 identified compounds (52.46% of monoterpenes and 42.09% of sesquiterpenes), CAR/PDMS fiber 22 identified compounds (55.05% of monoterpenes and 25.51% of sesquiterpenes), DVB/CAR/PDMS fiber 24 identified compounds (67.22% of monoterpenes and 23.88% of sesquiterpenes) and PDMS/DVB fiber 26 identified compounds (64.3% of monoterpenes and 30.93% of sesquiterpenes). The extractions with PDMS/DVB and DVB/CAR/PDMS fibers resulted in similar chemical profiles when compared to essential oil composition, in particular the triple-coated DVB/CAR/PDMS fiber which extracted more compounds with high retention time. Both of these fibers are the most suitable in an untargeted analysis of P. amboinicus volatiles, while PDMS and CAR/PDMS may be suitable for target compounds or classes of compounds. The data reported in this study demonstrates that HS-SPME coupled to GC-MS is a rapid and simple method of analysis and compose a valuable tool for the study of P. amboinicus volatiles.

Plectranthus neochilus Schltr. is an aromatic species, commonly used for digestive, antispasmodic, and analgesic purposes. Although many studies have reported the chemical composition of its essential oil, variations in the volatile profile were observed, which may be due to multiple factors linked to growth and field conditions. In order to detect metabolic variations in this species, we employed a GC-MS-based untargeted metabolomics approach analyzing samples of four P. neochilus individuals collected over a year. From all analyses, 24 mass features were detected and 21 were identified according to their respective chromatographic peaks. All features varied among samples, particularly (2E)-hexenal, 3-octanone and δ-3-carene, which showed the highest coefficient of variation percentage in our study. Although the four individuals presented the same peaks in the chromatograms, significant differences in the intensity of specific mass features were detected between individuals throughout the year. Time of sampling did not affect P. neochilus volatile composition; the chemical profile remained constant throughout the day. Seasonal trends were observed for the species. Winter months coincided with a drop in the intensity of most components. Air temperature showed a positive correlation with some feature intensities, while myrcene and α-thujene resulted in a positive and a negative correlation with rainfall, respectively. This study was the first attempt to correlate metabolic variation and environmental factors in P. neochilus. Our approach was successful in identifying the composition and variation of the headspace volatiles of P. neochilus leaves.

Background: Schinus terebinthifolius Raddi is a medicinal plant popularly known as pink pepper tree, commonly used for wound healing, anti-inflammatory and antimicrobial purposes. Furthermore, its fruit is used in culinary. Objectives: In order to further understand the composition and bioactivities of S. terebinthifolius essential oil from vegetative and reproductive parts of the tree, we evaluated the chemical composition and the antioxidant activity of Essential Oils (EO) obtained from different aerial parts of male and female plants. Materials and Methods:The EO was extracted by hydrodistillation; the antioxidant activity was evaluated via two in vitro assays with different mechanisms of action (DPPH and ORAC FL ) and the chemical composition was determined via GC-MS. Results: The EO from leaf, inflorescence and fruit of S. terebinthifolius showed distinct chemical profiles, yields and antioxidant potentials. Conclusion: The aerial parts of S. terebinthifolius may be used as a natural source of antioxidants, since all samples showed strong antioxidant capacity, mainly in the DPPH assay.

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