Півонія

Paeonia belongs to the order Saxifragales. Scientists differ on the number of species, from 25 to 40, but the current consensus describes 33 known species. Most are herbaceous perennial plants 0.25-1 metre tall, but some are woody shrubs 0.25-3.5 metres tall. They have large, often fragrant flowers, in colours ranging from purple and pink to red, white or yellow, in late spring and early summer. The flowers have a short blooming season, usually lasting for only 7-10 days.

Paeonia lactiflora, the Chinese peony, is native to central and eastern Asia, from eastern Tibet across northern China to eastern Siberia. Paeonia × suffruticosa is a perennial deciduous shrub with stems up to 2 m. It is the name used for most tree peony cultivars, but it is not a naturally occurring species. Currently there are about 600 Chinese tree peony cultivars.

Sensory evaluation of 87 herbaceous peony cultivars gave 16 cultivars with a strong scent, and their volatile components were identified by SPME-GC/MS. Terpenoids made up the largest share of the volatile components (60.94%), followed by fatty acid derivatives (24.57%) and benzenoids/phenylpropanoids (14.49%). Linalool and citronellol are the main aroma contributors, by odor activity value, in most strong-scented herbaceous peony cultivars, and geraniol and 2-PE in a few. The only strongly aromatic cultivar of the Itoh group, 'Lollipop', is mainly composed of linalool and phenylethyl alcohol. Hexanal and 2-hexenal were detected in all 17 cultivars studied. Geraniol was detected in 15 cultivars, and linalool and citral in 13. The sensory difference of flower fragrance among herbaceous peony cultivars is mainly due to the different contents of terpenoids and benzenoids/phenylpropanoids. Genes related to the biosynthesis of 2-PE, PlAADC1, PlPAR1 and PlMAO1, were detected in herbaceous peony petals, and a synthetic pathway for 2-PE was speculated.

Studies of fresh P. suffruticosa flowers have mostly focused on emitted volatiles, using headspace GC-MS or HS-SPME/GC-MS. The floral volatiles of tree peony cultivars mainly include (Z)-β-ocimene, α-pinene, citronellol, linalool, geraniol, neryl acetate, 2-phenylethanol and 1,3,5-trimethoxybenzene, among others. Results of studies on these volatiles vary considerably, most probably because of variations in cultivars. (Z)-3-hexen-1-ol and 1-hexanol are also found to be characteristic volatile components emitted from the buds. The main essential oil components of certain cultivars are heptadecane, heneicosane, 1,3,5-trimethoxybenzene, cis-linalool oxide (furanoid), trans-linalool oxide (furanoid) and α-terpineol, among others. Non-terpene oxygenated compounds were significantly higher in hydrolate extracts (24.2-96.6%) than in essential oils (11.7-62.5%) from the same cultivars. 2-Phenylethanol was not detected in the hydrolate extract of the cultivar 'BXT', whose chemotype was geraniol + citronellol + nerol (59.9%).

Phenethyl alcohol, or 2-phenylethanol, has the chemical formula C₈H₁₀O. It occurs widely in nature, being found in a variety of essential oils. Geraniol is a monoterpenoid alcohol and a primary component of rose oil. Citronellol, or dihydrogeraniol, is a natural acyclic monoterpenoid.