Chemical composition of hydrosol volatiles of flowers from ten Paeonia × suffruticosa Andr. cultivars from Luoyang, China

Abstract Hydrosol volatiles from flowers of ten Paeonia × suffruticosa Andr. cultivars were analysed by gas chromatography–mass spectrometry (GC-MS) and GC–flame ionisation detector (GC-FID) for the first time. Fifty components were identified representing 97.6–99.8% of total composition, in which oxygenated compounds (87.4–99.8%) predominated. Hydrosol volatiles of five and two cultivars presented chemotypes of 2-phenylethanol (48.0–79.5%) and 1,3,5-trimethoxybenzene (72.8%, 50.2%), respectively. Hydrosol volatiles of ‘XYTH’ rich in β-citronellol (57.2%) probably represented a newly defined chemotype with β-citronellol percentage over 50%. ‘GFCC’ hydrosol volatiles presented a balanced profile with 1,3,5-trimethoxybenzene (31.9%), β-citronellol (31.5%) and 2-phenylethanol (23.0%). ‘LHZL’ hydrosol volatiles were distinct from others due to occurrence of 6,9-heptadecadiene (2.0%), 2-heptanol (1.8%), pentadecane (1.5%), (Z)-3-nonen-1-ol (1.1%) and geraniol (15.7%). Chemotype characterisation of P. × suffruticosa Andr. hydrosols was of significance considering numerous cultivars of the species and potential applications of the hydrosols. Graphical Abstract


Introduction
Hydrosol is the condensate from hydro-distillation of aromatic plants. It may be the by-product obtained along with an essential oil (Rajeswara Rao et al. 2016), or the main product in cases of plant materials with low essential oil content (Prusinowska et al. 2016) or distillation without condensate recycling (Mulvaney 2012). Hydrosol volatiles are composed of organoleptically important, biologically active and polar volatile compounds (Lei et al. 2014;Lei et al. 2016aLei et al. , 2016b. They possess activities such as antimicrobial (Verma et al. 2016;Tabet Zatla et al. 2017), antioxidant (Prusinowska et al. 2016) and tyrosinase inhibition (Lante and Tinello 2015) effects, with applications in perfumes, cosmetics and aromatherapy.
Paeonia Â suffruticosa Andr. belongs to subfamily Paeonioideae within family Ranunculaceae. It is a deciduous shrub of up to 2 m tall and flowers during April. The flowers are double and petals are usually red, red-purple, pink or white (Yu et al. 1979). Known as national flower, the species is widely cultivated in China and hundreds of cultivars are known. The flower hydrosol is used in perfumes and cosmetics to improve skin health, and in aromatherapy to relieve stress and promote relaxation (Lei et al. 2018). However, there are few reports on chemical composition of hydrosol volatiles from different P. Â suffruticosa Andr. cultivars (Lei et al. 2018). In this work, ten well-known cultivars were investigated for the first time on chemical composition of hydrosol volatiles and variation with cultivars.

Results and discussion
Yields of hydrosol volatiles are listed in Table S1. Fifty compounds were identified accounting for 97.6 to 99.8% of total composition (Table S2). They were predominantly composed of oxygenated compounds (87.4-99.8%) whereas percentages of alkanes and alkenes were rather low ( 10.4%). Moreover, non-terpene oxygenated compounds (52.8-93.6%) were the main group for cultivars except for 'XYTH'. For 'XYTH', however, the main group was oxygenated terpenes (63.4%).

Disclosure statement
No potential conflict of interest was reported by the authors.

Funding
This work was supported by Scientific and Technological Project of Henan Province (182102310251) and Doctoral Startup Foundation of Henan University of Science and Technology (4020-13480039).