Elsevier

Phytochemistry

Volume 66, Issue 10, May 2005, Pages 1108-1112
Phytochemistry

Plocoralides A–C, polyhalogenated monoterpenes from the marine alga Plocamium corallorhiza

https://doi.org/10.1016/j.phytochem.2005.03.029Get rights and content

Abstract

Three new polyhalogenated monoterpenes, plocoralides A–C (13) along with three known compounds (46) have been isolated from the organic extract of the red alga P. corallorhiza. Structures of the new compounds were characterized as 4,8-dibromo-1,1-dichloro-3,7-dimethyl-2E,6E-octadiene (1), 4,6-dibromo-1,1-dichloro-3,7-dimethyl-2E,7-octadiene (2) and 4,8-dibromo-1,1,7-trichloro-3,7-dimethyl-2E,5Z-octadiene (3) on the basis of one- and two-dimensional NMR spectroscopic data and MS analyses. Compounds 26 show moderate cytotoxicity toward esophageal cancer cells.

Graphical abstract

Organic extracts of Plocamium corallorhiza contain three new polyhalogenated monoterpenes, plocoralides A–C (13). Compounds 13 show moderate activity towards esophageal cancer cells.

  1. Download : Download full-size image

Introduction

Red algae (Rhodophyta) of the genera Plocamium, Chondrococcus and Ochtodes produce a wealth of biologically active linear and cyclic polyhalogenated monoterpenes (Faulkner, 2002, Blunt et al., 2003). These metabolites exhibit a range of biological activities including antifeedant effects on reef herbivores (Paul et al., 1980, Paul et al., 1988, Sakata et al., 1991), antimicrobial (König et al., 1999), insecticidal (San-Martin et al., 1991, Argandona et al., 2002), antitubercular (König et al., 2000) and anticancer (Fuller et al., 1992, Fuller et al., 1994) activities. As part of a programme to investigate the chemistry of South African marine algae we have studied the non-polar constituents from Plocamium corallorhiza (Turner) Hooker & Harvey (Plocamiaceae, Plocamiales). P. corallorhiza is common and abundant in South Africa, often dominating large areas of rock in the subtidal fringe and shallow subtidal due to its masses of spreading coralloid attachment structures (hence the species name, meaning ‘coralloid roots’; Stegenga et al., 1997). This seaweed has also been reported from Namibia, Mozambique, St. Paul and Amsterdam Islands in the southern Indian Ocean, and Madagascar (Guiry and Nic Dhonncha, 2003). In South Africa, P. corallorhiza is harvested as feed for cultivated abalone (Anderson et al., 2003).

In the present work, we report on the isolation, structure elucidation and biological activity of three new ocimene-type polyhalogenated metabolites, plocoralides A–C (13) as well as three known compounds (46) from an organic extract of P. corallorhiza. The structures of compounds 13 are based on a regular isoprenoid carbon skeleton and are characterized by a rare 1,1-dichloro-2-ene moiety.

Section snippets

Results and discussion

Specimens of P. corallorhiza were collected from the intertidal zone at Kalk Bay near Cape Town, South Africa and immediately frozen. The partially thawed sample was extracted sequentially with MeOH and CH2Cl2. Fractionation of the CH2Cl2 extract by silica gel column chromatography (hexane–EtOAc) gave several fractions which were further purified by semi-preparative normal phase HPLC to yield compounds 16.

A molecular formula of C10H14Br2Cl2 was deduced from HREIMS and 13C NMR data for

General

Optical rotations were measured on a Perkin–Elmer 141 polarimeter. IR spectra were obtained as films on KBr disks using a Perkin–Elmer Spectrum 2000 FT-IR spectrometer. The 1H (400 MHz), 13C (100 MHz), DEPT-135, HMQC, HMBC, COSY-90 NMR spectra were all recorded on a Bruker Avance 400 NMR spectrometer using standard pulse sequences. Spectra were referenced to residual protonated solvent resonances (CHCl3 δH 7.25, δC 77.0). Compounds were purified using a Spectra-Physics IsoChrom LC HPLC system,

Acknowledgments

The authors thank Mr. Aubrey Sonemann (Chemistry Department, Rhodes University) for recording low-resolution mass spectra and the South African Department of Environmental Affairs and Tourism for a marine research permit. This research was supported by grants from Rhodes University and the South African National Research Foundation (REDIBA Program).

References (23)

  • P. Crews et al.

    Halogen regiochemistry and substituent stereochemistry determination in marine monoterpenes by 13C NMR

    Journal of Organic Chemistry

    (1984)
  • Cited by (36)

    • Occurrence and fate studies (sunlight exposure and stable carbon isotope analysis) of the halogenated natural product MHC-1 and its producer Plocamium cartilagineum

      2020, Science of the Total Environment
      Citation Excerpt :

      Despite the identification of its producer, it was largely unclear how MHC-1 (Fig. 1a) is entering the marine food web. Moreover, Plocamium sp. is known to produce several other halogenated monoterpenes (including three further C10H13Br2Cl3 isomers (Fig. 1b–d)) (Knott et al., 2005; Stierle and Sims, 1979). However, usually only MHC-1 was reported to occur in higher organisms.

    • Halogenated monoterpenes from Namibian Plocamium rigidum: Accurate quantification and chemotaxonomic relevance

      2020, South African Journal of Botany
      Citation Excerpt :

      It has been postulated that halogenated compounds are also used to assist in anti-fouling and reduce space competition amongst competing marine algae (Dworjanyn et al., 1999). These halogenated secondary metabolites exhibit a range of biological activities including antifeedant effects on reef herbivores, antimicrobial, insecticidal, antitubercular and anticancer activities (Knott et al., 2005). The major metabolite found in P. rigidum has been a topic of major interest for several years.

    • Plaxenone A and B: Cytotoxic halogenated monoterpenes from the South African red seaweed Plocamium maxillosum

      2019, Phytochemistry Letters
      Citation Excerpt :

      Fortunately, several recent enantioselective total syntheses (Vogel et al., 2014; Hu et al., 2015; Braddock et al., 2014) have opened up opportunities for the further development of these molecules as anticancer leads. In continuation of our investigation of biologically active natural products from South African Plocamium species (Knott et al., 2005; Mann et al., 2007; Afolayan et al., 2009), we have studied Plocamium maxillosum (Poiret) J.V. Lamouroux, a seaweed endemic to southern Africa (Stegenga et al., 1997; Silva et al., 1996). Herein we describe the isolation and characterization, as well as the cytotoxic activity, of two novel halogenated monoterpene cyclohexanone derivatives, plaxenone A and B (1 and 2) from the organic extracts of P. maxillosum.

    • Chemical composition of seaweeds

      2015, Seaweed Sustainability: Food and Non-Food Applications
    • Monoterpenes and Related Compounds from the Medicinal Plants of Africa

      2013, Medicinal Plant Research in Africa: Pharmacology and Chemistry
    View all citing articles on Scopus
    View full text