The chemistry of flower rewards -- Oncidium (Orchidaceae)

Abstract

A maioria dos estudos sobre polinização focalizam as interações que envolvem recompensas como néctar e pólen. Nosso grupo de pesquisa, entretanto tem se dedicado à química de recompensas florais como resinas e óleos florais. Neste trabalho, estamos relatando a composição química dos óleos florais de Oncidium pubes que contêm di e triacilglicerois nos quais o glicerol está esterificado com um ou dois resíduos de ácido acético e um ácido graxo. O padrão de substituição dos dracilgliceróis foi sugerido com base nas analises espectroscópicas e por comparação com os 3 compostos sintetisados a partir do D-manitol, ácido acético e ácido oleico Finalmente, nossos resultados forneceram evidências químicas de que a polinização de Oncidium pubes não está baseada num mecanismo de atração-engano dos visitantes florais mas na sua recompensa com lipídios florais. Este é o primeiro relato sobre a composição química dos óleos florais de Oncidium pubes (Orchidaceae).Most of the flower-pollinator interactions are based on rewards as pollen and nectar. Our group however, has been focusing on the chemical composition of unusual rewards like floral resins and floral oils. We are now reporting the chemistry of the floraloils of Oncidium pubes which are composed of diacylglycerols and triacylglycerols possessing one or two acetyl residues and one long chain fatty acid. The substitution pattern of some of the diacylglycerols was inferred to be 1, 3 based on spectroscopic analyses and comparison with 3 different synthetic compounds obtained from D-mannitol, oleic acid and acetic acid. The fatty acid residues possess double bond and/or acetoxy group as functional groups. Finally our results provided chemical evidences that pollination of Oncidium pubes is not based upon an attraction-deception system but on floral lipids and this is the first time this has ever been mentioned in the literature.

Non-volatile floral oils of Diascia spp. (Scrophulariaceae)

“…They were detected in amounts lower than 1% ( Table 2). Some of these compounds were also reported from Oncidium oil (Reis et al, 2000). EI mass spectra of 1-acyl-2,3-diacetyl-glycerols were also previously described (Reis et al, 2003).…”

“…doi:10.1016/j.phytochem.2007.12.012 b-acetoxy fatty acids were found as main lipid components (Vogel, 1969(Vogel, , 1974(Vogel, , 1986(Vogel, , 1990Simpson et al, 1977Simpson et al, , 1979Seigler et al, 1978;Cane et al, 1983;Simpson and Neff, 1983;Buchmann, 1987;Vinson et al, 1997). The structure of a novel diacylglycerol of Ornithophora radicans was elucidated from spectroscopic data (Reis et al, 2000(Reis et al, , 2003. Our group was first to report partially acetylated 3,7-dihydroxy fatty acids as a new type of constituent in Malpighia coccigera (Malpighiaceae) oil; and to discuss a possible relationship between floral oil and plant epicuticular wax biosynthesis.…”

Oncidinol—a novel diacylglycerol from Ornithophora radicans Barb. Rodr. (Orchidaceae) floral oil

“…Flower pollination occurs during floral oil collection 2 and we were thus motivated to study the chemical composition of floral oils belonging to 30 different species of the subtribe Oncidiinae. We have found that the major components of the floral oils of Oncidium pubes Lindl., 3 4 Asymmetrically substituted diacylglycerols are known to activate the protein kinase C (PKC), responsible for the cellular signal transductions that promote lipid hydrolysis and phosphorylation of a variety of target proteins which control growth and cellular differentiation. 5 Therefore the role of these floral oils in the bees% lives may be more important than just nest material.…”

Orchid Biology: Reviews and Perspectives, X

“…The oils of certain other members of the 'Gomesa clade' such as Oncidium enderianum auct. and related taxa also contain diacylglycerol derivatives but here, the compounds are not exuded (Reis et al, 2000).…”

“…and Zygostates lunata Lindl. (Reis et al, 2000(Reis et al, , 2003 although, remarkably, that of P. delicatulum is composed largely of linear hydrocarbons . The major component of the floral oil of Ornithophora radicans is (2S, 3'R, 7'R)-1-acetyl-2-(3', 7'-diacetoxy-eicosanoyl)-glycerol (Reis et al, 2003) and acylglycerols are thought also to occur in the floral oils of Oncidium loefgrenii Cogn.…”