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Volatile‐Oils Composition, and Bioactivity of the Essential Oils of Plectranthus barbatus, P. neochilus , and P. ornatus Grown in Portugal
Author(s) -
Mota Luísa,
Figueiredo A. Cristina,
Pedro Luís G.,
Barroso José G.,
Miguel M. Graça,
Faleiro M. Leonor,
Ascensão Lia
Publication year - 2014
Publication title -
chemistry and biodiversity
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.427
H-Index - 70
eISSN - 1612-1880
pISSN - 1612-1872
DOI - 10.1002/cbdv.201300161
Subject(s) - chemistry , plectranthus , botany , pinene , essential oil , lamiaceae , alpha pinene , sesquiterpene , food science , monoterpene , chemical composition , dpph , limonene , antioxidant , organic chemistry , biology
Volatile‐oils chemical composition and bioactivity of the essentail oils from Plectranthus barbatus, P. neochilus , and P. ornatus (Lamiaceae) were assessed. Aerial parts from these three related Plectranthus species were collected from cultivated plants grown in Portugal, during vegetative and flowering phases. Volatiles, isolated by distillationextraction, were analyzed by GC and GC/MS. Monoterpene hydrocarbons (12–74%) and sesquiterpene hydrocarbons (4–45%) constituted the main fractions in all volatiles. α ‐Pinene ( 3 ; 12–67%), oct‐1‐en‐3‐ol ( 6 ; traces–28%), β ‐pinene ( 7 ; 0.1–22%), and β ‐caryophyllene ( 50 ; 7–12%) dominated P. barbatus volatiles. P. neochilus major volatile components were α ‐terpenyl acetate ( 41 ; traces–48%), α ‐thujone ( 2 ; 2–28%), β ‐caryophyllene ( 50 ; 2–28%), β ‐pinene ( 7 ; 1–25%), and α ‐pinene ( 3 ; 1–19%). Oct‐1‐en‐3‐ol ( 6 ; 13–31%), β ‐pinene ( 7 ; 11–24%), α ‐pinene ( 3 ; 11–19%), and β ‐caryophyllene ( 50 ; traces–11%) were the main constituents from P. ornatus volatiles. These chemical compositions were rather different from those previously found for specimens harvested in Africa and Brazil. Moreover, the volatiles from the flowers are herewith reported for the first time. Essential oils, isolated by hydrodistillation from leaves and stems, showed a yellowish color and unpleasant odor, with yields ranging from 0.08% to 0.84% ( v /dry weight). Antioxidant and antimicrobial activities of the essential oils were evaluated by DPPH . and TBARS assays, and agar disc‐diffusion method, respectively. Results showed low or moderate antioxidant capacity and significant antimicrobial activity against Gram ‐positive bacteria.