P. rubra flowers were found to contain tannins, flavonoids, terpenoids, reducing sugars and alkaloids (Egwaikhide et al. 2009). Two iridoid diastereoisomers were isolated from the flowers of Plumeria rubra cv. acutifolia (Ye et al. 2008). A new iridoid alkaloid containing a spironolactone unit, plumericidine, was isolated from the flowers of Plumeria rubra L. cv. acutifolia (Ye et al. 2009). Two anthocyanins cyanidin 3-O-β-(2″-glucopyranosyl-O-β-galactopyranoside) (75 %) and cyanidin-3-O-β-galactopyranoside (20 %) were isolated from ornamental reddish flowers of Plumeria rubra (Byamukama et al. 2011).

Norsita et al. (2006a) reported P. rubra pink flowers to have the following main volatile constituents: lauric acid (30.8 %), myristic acid (17.4 %), palmitic acid (9.8 %), nonadecane (8.2 %), methyl stearate (5.6 %), linalool (4.8 %), docosane (2.8 %) and tricosane (2.8 %); P. rubra orange flowers to have linalool (3.3 %), α-fenchyl alcohol (2.1 %), geraniol (4.1 %), (E)-nerolidol (14.4 %), caryophyllene oxide (3.1 %), (E,E)-farnesol (4.4 %), benzyl benzoate (8.6 %), myristic acid (2.9 %). 2-phenyl benzoate (3.9 %), benzyl salicylate (20.9 %), 2,6,10,14-teyramethylheptadecane (2.8 %), neryl phenylacetate (4.1 %), palmitic acid (4.4 %) and ethyl palmitate (3.1 %); reddish-orange flowers to have n-nonadecane (3.6 %), n-heneicosane (4.1 %), tricosane (3.6 %), docosane (2.7 %), pentyl benzoate (4 %), benzyl benzoate (4 %), phenylethyl benzoate (12.3 %), benzyl salicylate (4.1 %), methyl stearate (3.4 %), phenylethyl cinnamate (2 %), lauric acid (11.8 %), myristic acid (3.9 %), palmitic acid (9.3 %) and linalool (5.3 %); P. rubra red flowers to have n-nonadecane (2 %), methyl stearate (3.3 %), lauric acid (10.6 %), myristic acid (18.9 %), palmitic acid (27.2 %), linoleic acid (20.7 %), linalool (2.1 %) and terpinene-4-ol (3.7 %). Norsita et al (2006b) also reported P. acuminata yellowish-white flowers to have the following main volatile components: benzyl salicylate (39 %), benzyl benzoate (17.2 %), (E)-nerolidol (10.6 %), neryl phenylacetate (10.5 %), linalool (8.9 %), cinnamyl cinnamate (2.9 %), geranial (2.6 %) and camphor (1.9 %) and P. acuminata yellow flowers to have palmitic acid (36.2 %), linoleic acid (16.8 %), lauric acid (10.4 %), myristic acid (10.3 %), pentacosane (8.1 %), tricosane (%.1 %) methyl stearate (4.4 %). Earlier Pino et al. (1994) reported the following main volatiles from P. rubra var. acutifolia flowers: n-butyl oleate (13.8 %), n-butyl palmitate (11.5 %), methyl palmitate (9.7 %), methyl oleate (9.3 %), linalool (8.2 %), α-terpineol (7.63 %), cinnamyl alcohol (6.3 %), n-butyl stearate (5.3 %), benzoic acid (4.3 %), trans, trans-farnesol (3.2 %) and methyl stearate (2.8 %).

The major volatile constituents of Plumeria rubra white-yellow flowers (L2) were l-linalool, benzaldehyde 22.07 %, methyl salicylate 8.1 %, nerolidol 4.65 %, trans-β-ocimene 3.28 % and geranial 3.08 % (Chitsamphandhvej 2010). The major volatile constituents of Plumeria sp. pink flowers (L1) were l-linalool 37.61 %, benzene ethanol 20.71 %, trans-geraniol 12.66 %, methyl benzoate 8.86 %, benzene acetonitrile 3.73 %, linalool oxide 3.37 % and nerolidol 0.95 %. The major volatile constituents of Plumeria rubra, Leung Angthong (L3) flowers, were trans-β-ocimene 48.73 %, benzene methanol 12.1 %, benzene ethanol 8.98 %, methyl salicylate 7.18 %, methyl benzoate 6.21 %, l-linalool 4.68 %, trans-geraniol 3.06 %, benzene acetonitrile 2.9 %, benzaldehyde 1.46 % and linalool oxide 1.03 %. The major volatile constituents of Plumeria rubra red flowers (L5) were isoamyl alcohol 17.96 %, trans-geraniol 11.86 %, benzene ethanol 8.51 %, 2-methyl-1-butanol 6.01 %, 2-methyl-2-butenal 4.47 %, benzene acetonitrile 2.34 %, methyl benzoate 1.16 % and l-linalool 1.15 %.

A total of 74 compounds were identified in the essential oil of Plumeria rubra forma acutifolia (Poir.) Woodson cv. ‘Common Yellow’ flowers (Omata et al. 1991). Linalool (14.1 %), phenylacetaldehyde (16.1 %), trans, trans-farnesol (11 %), β-phenylethyl alcohol (8.8 %), geraniol (5.4 %), α-terpineol (2.8 %), neral and geranial were found to make a major contribution to the floral scent of the flower, the last two comprised 0.9 %. A total of 67 compounds were identified in the essential oil of Plumeria rubra ‘Irma Bryan’ flowers (Omata et al. 1992). β-phenylethyl alcohol (31.6 %), phenylacetaldehyde (12.1 %) and methyl cinnamate (1 %) were found to make a major contribution to the floral spicy scent of the flower, while 2-methylbutan-1-ol (10.5 %) did not contribute to its scent. Forty-three components were identified from the flower essential oil of Plumeria rubra var. acutifolia (Li et al 2006). The main components were fatty acid such as hexadecanoic acid, dodecanoic acid and linoleic acid; other components included terpenoids such as trans-nerolidol, β-linalool and trans-geraniol. Sixteen compounds were identified from the flower essential oil of Plumeria rubra cv. acutifolia (Han 2007). The major components in essential oil were nerolidol (20.25 %) and geranyl linalool isomer (10.1 %). Other main content components were heptacosane (7.65 %), tetradecanoic acid (6.73 %), hexadecanoic acid, 2,3-dihydroxypropyl ester (2.98 %) and 1,2-benzenedicarboxylic acid, bis(2-methylpropyl) ester (2.68 %). The main components of the essential oil of Plumeria rubra var. acutifolia extracted by supercritical carbon dioxide fluid extraction comprised 1, 6, 10-dodecatrien-3-ol; 3,7,11-trimethyl; benzoic acid; 2-hydroxy-, phenylmethyl ester; 1,2-benzenedicarboxylic acid; and bis(2-methylpropyl) ester (Xiao et al. 2011). The last components comprised 66.11 % of the total.

Seven compounds, namely, 2-methylbutan-1-ol, β-phenylethyl alcohol, nonadecane, heneicosane, benzyl salicylate, tetradecanoic acid and phenylacetaldehyde were found in the essential oil of P. rubra red flower variety; 19 compounds, namely, a-terpineol, geraniol, β-phenylethyl alcohol, nonadecane, heneicosane, trans-farnesol, benzyl benzoate, geranial, dodecanoic acid, benzyl salicylate, phenylethyl benzoate, tetradecanoic acid, tetracosane, octadecanoic acid, tricosane, docosane, eicosane and phenylacetaldehyde in the yellow flower variety; and 14 compounds in P. obtusa (Sulaiman et al. 2008). The major components found in all three species were 2-hydroxybenzoic acid phenylmethyl ester. All three also shared two alkane hydrocarbons, nonadecane and heneicosane.

Albers-Schönberg and Schmid (1961) isolated isoplumericin, β-dihydroplumericin and β-dihydroplumericin along with plumericin from Plumeria rubra var. alba. They also isolated β-dihydroplumericinic acid from the same source and also fulvoplumierine (Albers-Schönberg et al. 1962). Stearic acid was isolated from leaf and stem of P. rubra, and flavonoids quercetin, quercitrin found in the leaf, flower and stem of Plumeria rubra and Plumeria rubra var. alba (Mahran et al. 1974b).

Taraxasteryl acetate, lupeol, stigmasterol, oleanolic acid, cycloart-22-ene-3 α,25-diol and rubrinol, a new triterpene of the ursane series, were isolated from whole plants of P. rubra (Akhtar et al. 1994). The structure of rubrinol was elucidated as 3 β,30-dihydroxy-12-ursene. Two new oleanene-type triterpenes 6α-hydroxy-3-epi-oleanolic acid and 3α,27-dihydroxy-olean-12-ene were isolated from Plumeria rubra (Akhtar and Malik 1993).

Acidic proteins with molecular masses between 12.5 and 74.5 kDa predominated in laticifers of P. rubra (de Freitas et al. 2010). Strong antioxidative activity of superoxide dismutase was detected in P. rubra latices, and to a lesser extent ascorbate peroxidase and isoforms of peroxidase were observed. In laticifer cells of P. rubra, four proteinases were detected, including cysteine and serine types. A protease with molecular weight of approximately 81.85 kDa was purified from the latex of Plumeria rubra plant and given the trivial name, plumerin-R (Chanda et al. 2011). It remained active over a broad range of temperature but had optimum activity at 55 °C and pH 7.0 when casein was used as substrate. Activation of the protease by a thiol-activating agent indicated the presence of sulfhydryl as an essential group for its activity.