Frangipani

Botany

Plumeria species are native to the Neotropical realm in Mexico, Central America, the Caribbean, and northwestern South America. They are often grown as ornamental plants in tropical regions, including Florida, Hawaii, southern China, northern India and Senegal. The branches are succulent, and the trunk and branches have a milky latex sap that, like the sap of many other Apocynaceae, contains poisonous compounds that irritate the eyes and skin. Plumeria trees flower from early summer to fall. The blossoms grow in clusters at the ends of the stems and have a tubular corolla that splits sharply into five rounded, waxy petals that overlap each other. The flowers come in many colours, including pink, red, white, yellow, orange or pastel. The genus Plumeria includes 18 accepted species and one natural hybrid.

The scent of the flowers tricks sphinx moths into pollinating them as the moths search in vain for nectar. In Plumeria rubra the fragrance becomes more prominent in the evening and at night, matching the period of greatest hawkmoth activity. Plumeria rubra grows as a spreading tree 7-8 m (23-26 ft) high and wide that is flushed with fragrant flowers in shades of pink, white and yellow over the summer and autumn. Despite its common name, Plumeria rubra is not a true jasmine and does not belong to the genus Jasminum. The native range of Plumeria rubra extends from Baja California into central Mexico and south through Central America to the Department of Antioquia in Colombia and Venezuela. Plumeria rubra is cultivated widely in tropical and subtropical regions of the world and has become naturalized in most parts of tropical Asia and the Pacific Islands. Plumeria alba is native to Puerto Rico and the Lesser Antilles in the Caribbean. It is a small deciduous tree that has been planted in tropical regions worldwide. The flowers of Plumeria alba are fragrant, with five white petals and a yellow center.

Scent chemistry

Linalool (23.91%), alpha-terpineol (10.97%), geraniol (10.47%) and phenylethyl alcohol (8.65%) are abundant in the essential oil of Plumeria alba flowers, in which 17 compounds were identified. Terpenes and terpenoids dominate that flower oil, which also holds primary alcohols, ketones, esters and saturated fatty acids. A reported analysis of Plumeria alba flowers from India gives benzyl salicylate (33.98%), benzyl benzoate (12.37%), germacrene (10.30%) and linalool (8.71%) as major compounds. In the headspace of Plumeria rubra flowers, (E,E)-alpha-farnesene makes up 40.9-41.2% of the volatiles on the DB-5ms column and (E)-nerolidol 21.4-32.6%. (E)-beta-Ocimene, (Z)-dihydro-apofarnesol, linalool and perillene are the other main constituents. Another analysis of Plumeria rubra flowers reported benzyl salicylate (26.7%), benzyl benzoate (22.3%), (E,E)-geranyl linalool (9.4%) and tricosane (8.3%) among the main constituents.

Open flowers of plumeria emit the highest amount of volatiles, with phenylpropanoids and benzenoids (70.1%) outweighing terpenoids (20.8%). Open flowers emit nearly 6 times more total volatiles than floral buds and 2.5 times more than leaves. 2-Phenylethanol is the most abundant volatile of open plumeria flowers, at 35.67% of the total. Benzaldehyde (11.77%) and 2-phenylacetaldehyde (5.82%) are also among the open-flower volatiles. Floral buds emit mainly terpenoids, such as eucalyptol (51.68%). The leaves emit mainly monoterpenoids, such as beta-ocimene (55.53%). A highly expressed, flower-specific gene encoding a cytochrome P450 protein, PrCYP79D73, catalyzes the formation of phenylacetaldoxime in plumeria flowers. Phenylacetaldoxime is an intermediate in the biosynthesis of 2-phenylethanol in plumeria flowers. 2-Phenylethanol is likely of major importance to the typical scent and fragrance of plumeria flowers.

Uses and culture

In several Pacific islands, including Tahiti, Fiji, Samoa, Hawaii, New Zealand, Tonga and the Cook Islands, Plumeria species are used for making leis. Balinese Hindus use the flowers in their temple offerings. In Cambodia pagodas especially choose Plumeria alba, and its flowers are used in ritual offerings to the deities. The flowers of Plumeria alba are edible and eaten as fritters. In Myanmar the poisonous sap is used as a laxative. Plumeria is considered a symbol of immortality because it can flower and produce leaves even if uprooted. Plumeria rubra is the national flower of Laos, where it is known as dok champa. Plumeria rubra was declared the national flower of Nicaragua in 1971, where it is known as sacuanjoche. In Mexico the common name of Plumeria rubra is cacaloxochitl, a Nahuatl name meaning crow's flower. Because of its associations with graveyards and death, Plumeria rubra is also known as bunga kuburan, literally grave flower.