Gas Chromatography-Mass Spectrometry (GC-MS) Combined with Retention Index Prediction for the Rapid Identification of Halogenated monoterpenes from a Namibian Plocamium species.

Plocamiun species collected from the Namibian coast display morphological features similar to those of both P. rigidum and P. suhrii which makes identification of these species a difficult task. It has been reported that the major secondary metabolites found in various Plocamium species are unique to each species [1]. In this study GC-MS combined with a retention index (RI) prediction strategy was used for the rapid identification of halogenated monoterpenes characteristic of a particular Namibian Plocatnium species. The RIs of the metabolites were matched with the predicted RIs of halogenated monoterpenes for which similar MS data have been reported for the same species of Plocamium. Based on the identification of the major secondary metabolite, IE,3R,4S,5E,7Z- 1-bromo-3;4,8- trichloro-7-(dichloromethyl)-3-methylocta-1,5,7-triene [2], it was proposed that these Namibian samples are closely related to that of P. suhrii. From. this, it was determined that the proposed P. suhrii specimens collected in Namibia contain four additional metabolites (with molecular formulae C10H16Br2C2, C10H11BrCI4, C10H9BrCl6 and an unknown compound) previously not reported in P. suhrii species. In addition, a compound previously identified in South African P. suhrii was not present in the Namibian Plocamium specimens.

Identification and in vitro anti-esophageal cancer activity of a series of halogenated monoterpenes isolated from the South African seaweeds Plocamium suhrii and Plocamium cornutum.

Five known (1, 2, 4, 6 and 7) halogenated monoterpenes together with 1Z,3R∗,4S∗,5E,7Z)-1-bromo-3,4,8-trichloro-7-(dichloromethyl)-3-methylocta-1,5,7-triene (3) and (3R∗,4S∗)-3,4,6,7-tetrachloro-3,7-dimethyl-octen-1-ene (5) were isolated from the red macroalga Plocamium suhrii and their structures deduced from their spectroscopic data. The seven compounds from P. suhrii together with five related compounds from Plocamium cornutum have been evaluated for their cytotoxic effects on an esophageal cancer cell line (WHCO1). Compounds 1-6 showed greater cytotoxicity in this assay as compared to the known anticancer drug cisplatin.

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

Three new polyhalogenated monoterpenes, plocoralides A-C (1-3) along with three known compounds (4-6) 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 2-6 show moderate cytotoxicity toward esophageal cancer cells.