Abstract
The species Plectranthus amboinicus is an aromatic herb with great application in popular medicine due to the diversity of biological properties. Chemically, its essential oil (EO) is characterized by two chemotypes, thymol and carvacrol, which vary depending on factors such as seasonality. Despite being an extensively exploited species, studies of the bioherbicidal potential of this species are insufficient. In this context, the EO of P. amboinicus leaves, extracted in two different seasonal periods, were characterized regarding chemical profile (by gas chromatography mass spectrometry - GC-MS) and thermal profile (DTG) and was subjected to bioherbicide tests (germination test and seedling development) against Eragrostis plana, commonly known as capim annoni, an invader of pastures in the Pampas region. P. amboinicus EO was a potent inhibitor of E. plana germination, reducing accumulated germination by over 70% when exposed to 0.1% EO, and a complete inhibition of germination was observed when exposed to 0.5%. Following the effects observed in germination, the initial growth of E. plana was significantly affected by concentrations above 0.05%. The major constituent identified via GC-MS was carvacrol, representing 87.5% of the volatile composition of P. amboinicus leaves. In addition, P. amboinicus EO presented high thermal stability up to 100 °C, which is an interesting result regarding its use as a bioproduct.
Highlights
Plectranthus amboinicus, known as country borage, is a dicotyledonous plant belonging to the family Lamiaceae [1]
The comparison between the oil yields obtained in winter (0.2582 ± 0.0781) and summer (0.2680 ± 0.0126), as well as the chemical profile of the essential oils (EOs) samples, showed that the environmental conditions in these two periods of the year did not significantly affect the metabolism of P. amboinicus
From the analysis of the chemical profile, the predominance of terpene class was observed with the majority production of carvacrol chemotype, representing an average of 87.5% of the volatile composition of P. amboinicus leaves (Table 1)
Summary
Plectranthus amboinicus, known as country borage, is a dicotyledonous plant belonging to the family Lamiaceae [1]. It is a large succulent aromatic perennial herb [2]. The species, known as “thick-mint”, has been used for long as a medicinal plant for many diseases such as respiratory diseases, hepatopathy, renal and vesical calculi, to treat malarial fever, cough, chronic asthma, J. Some studies provide evidence for its folkloric medicinal uses, such as its analgesic and anti-inflammatory activities [6]. Patel et al (2010) [7], found significant antioxidant activity. Antimicrobial [5, 8] and insecticidal potential [9] were investigated
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