Chemical analysis of incense smokes used in Shaxi, Southwest China: A novel methodological approach in ethnobotany

Aim of the study: Characterization and comparative analysis of the main VOCs (volatile organic compounds) present in the smoke of 11 experimentally combusted plant species used as incense in Shaxi, Southwest China. Substances which may be responsible for the pleasant smell of the smokes as well as substances with a potential pharmacological activity are discussed. Materials and methods: We adopt the dynamic headspace sorption method for the collection of smoke samples as a novel methodological approach in ethnobotany. The VOCs were identified using gas chromatography-mass spectrometry (GC-MS). Principal component analysis and canonical discriminant analysis were performed using PASW statistics (Version 18.0.2). Results: Among the identified compounds were 10 monoterpenoids, 7 sesquiterpenoids, 6 linear hydrocarbons, 6 methoxy phenolics, 2 benzenoids, 2 polycyclic aromatic hydrocarbons, and 2 fatty acids. Based on their volatile profiles, the species are well clustered intraspecifically and separated interspecifically. The most abundant among the compounds potentially responsible for the pleasant smells of the smokes are methyl salicylate (12.28 ± 3.90%) for Gaultheria fragrantissima leaves, δ-cadinene (15.58 ± 2.29%) for Juniperus squamata wood, and α-Pinene for Cupressus funebris branches (9.16 ± 7.73%) and Pistacia weinmanniifolia branches (19.52 ± 8.66%). A couple of substances found are known for pharmacological activity, such as methylsalycilate, beta-caryophyllene and cedrol. Conclusions: The species used by the local people in Shaxi for incense differ clearly with respect to the chemical compounds of their smoke. Further, incense contains substances, which are of pharmacological interest and might support medicinal uses of smoke. Cedrol with its pleasant smell and sedative properties may be an important factor why specific plants are chosen as incense. Our findings support the idea that the effects of the use of incense as well as medicinal smoke depend on both, the cultural as well as the pharmacological context.