Floral scent in a sexually deceptive Ophrys orchid: from headspace collections to solvent extractions

The volatile chemistry of orchid pollination

Covering: up to September 2022Orchids are renowned not only for their diversity of floral forms, but also for their many and often highly specialised pollination strategies. Volatile semiochemicals play a crucial role in the attraction of a wide variety of insect pollinators of orchids. The compounds produced by orchid flowers are as diverse as the pollinators they attract, and here we summarise some of the chemical diversity found across orchid taxa and pollination strategies. We focus on compounds that have been experimentally demonstrated to underpin pollinator attraction. We also highlight the structural elucidation and synthesis of a select subset of important orchid pollinator attractants, and discuss the ecological significance of the discoveries, the gaps in our current knowledge of orchid pollination chemistry, and some opportunities for future research in this field.

Orchidaceae-Derived Anticancer Agents: A Review

Simple Summary

Orchids are commonly used in folk medicine for the treatment of infections and tumors but little is known about the actual chemical composition of these plants and their anticancer properties. In this paper, the most recent literature on orchid-derived bioactive substances with anticancer properties is reviewed. According to the published data, numerous species of orchids contain potential antitumor chemicals. Still, a relatively insignificant number of species of orchids have been tested for their bioactive properties and most of those studies were on Asian taxa. Broader research, ’including American and African species, as well as the correct identification of samples, is essential for evaluating the usefulness of orchids as a plant family with huge anticancer potential.

Abstract

Species of orchids, which belong to the largest family of flowering plants, are commonly used in folk medicine for the treatment of infections and tumors. However, little is known about the actual chemical composition of these plants and their anticancer properties. In this paper, the most recent literature on orchid-derived bioactive substances with anticancer properties is reviewed. For the assessment, previous papers on the anticancer activity of Orchidaceae published since 2015 were considered. The papers were found by exploring electronic databases. According to the available data, many species of orchids contain potential antitumor chemicals. The bioactive substances in a relatively insignificant number of orchids are identified, and most studies are on Asian taxa. Broader research on American and African species and the correct identification of samples included in the experiments are essential for evaluating the usefulness of orchids as a plant family with vast anticancer potential.

A Semivolatile Floral Scent Marks the Shift to a Novel Pollination System in Bromeliads

Perfume flowers (sensu Vogel¹) produce intense scents that function both as attractants and as the sole rewards for pollinators. The scent is collected exclusively by male euglossine bees and used during pre-mating behavior.^2-5 Perfume flowers have evolved independently in 15 angiosperm families, with over 1,000 reported species across the Neotropical region.⁶ Members of Cryptanthus (Bromeliaceae) represent a puzzling exception among perfume flowers, as flowers produce nectar and do not emit a noticeable scent yet still attract euglossine males.⁷ Here, we studied the pollination ecology of Cryptanthus burle-marxii and decode the chemical communication between its flowers and euglossine males. Field observations revealed euglossine males and hummingbirds as potential pollinators. The bees always contacted anthers/stigma of C. burle-marxii while scraping the petals to obtain chemicals, whereas nectar-seeking hummingbirds normally only contacted the anthers. Based on gas chromatography-mass spectrometry/nuclear magnetic resonance analyses of flower scent samples and bioassays, we identified the diterpene copalol as the only floral scent compound triggering scent-gathering behavior in euglossine males. Unlike euglossine-bee-mediated pollination, hummingbird pollination is ancestral in the Cryptanthus clade, suggesting a case of an ongoing pollinator shift^8-10 mediated by the evolution of perfume as a reward. Copalol was previously unknown as a floral scent constituent and represents the heaviest and least-volatile compound known to attract euglossine males. Our study provides the first experimental evidence that semivolatile floral compounds can mediate euglossine bee interactions. Male euglossine pollination in other plant species lacking noticeable floral scents^11-13 suggests that semivolatile-mediated pollinator attraction is more widespread than currently appreciated.