Characterisation of volatile compounds from the leaves of six Pittosporum species; an instrumental and sensory evaluation
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Six Pittosporum species native to New Zealand, P. cornifolium, P. crassifolium, P. eugenioides, P. kirkii, P. tenuifolium, and P. umbellatum, were investigated in this study. The 88 volatile compounds released from their leaves were identified by head space SPME whose optimized conditions are fibre coating PDMS, extraction time 30mins and extraction temperature 70°C with GC-MS analysis. Most of these volatile compounds were identified as sesquiterpenes, 21 of which were shown to be major constitutes in the Pittosporum species. They are α-pinene, sabinene, β-pinene, β-myrcene, limonene, α-copaene, (-)-β-bourbonene, β-cubebene, α-gurjunene, β- caryophyllene, cis-thujopsene, humulene, alloaromadendrene, γ-muurolene, germacrene D, β-cadinene, bicyclo[3.1.1]hept-2-ene, 2,6-dimethyl-6-(4-methyl-3-pentenyl)-, naphthalene, 1,2,4a,5,6,8a-hexahydro-4,7-dimethyl-1-(1-methylethyl)-, bicyclo[2.2.1]heptane, 2-methyl-3-methylene-2-(4-methyl-3-pentenyl)-, (1S-endo)-, 4,4-dimethyl-3-(3-methylbut-3-enylidene)-2-methylenebicyclo[4.1.0]heptane and cyclohexane, 1-ethenyl-1-methyl-2-(1-methylethenyl)-4-(1-methylethylidene)-. The main components in P. cornifolium, P. crassifolium, P. eugenioides, P. kirkii, P. tenuifolium, and P. umbellatum are germacrene D, α-copaene, nonane, germacrene D, β-caryophyllene and cyclohexane, 1-ethenyl-1-methyl-2-(1-methylethenyl)-4-(1-methylethylidene)-, respectively. The GCMS fingerprint spectra clearly showed the difference of these plants. Six of the Pittosporum species were also subjected to projective mapping of their odour profiles. This showed “green” and “sweet” as general descriptors for all the Pittosproum. However, P. kirkii and P. cornifolium were also described as “fruity” and “floral”. The aromas of P. umbellatum, P.tenuifolium and P. crassifolium as “bitter”, “woody” and “grassy” with a sense of “spicy” and P. eugenioides as having a “citrus” odour.