Some marine algae from Ceylon - 2. Laurencia lamouroux

The herbarium material belonging to the genus Laurencia kept at the Royal Botanical Gardens, Peradeniya together with my collections of material belonging to this genus from various parts of Ceylon have been examined. Most of the material belonging to the genus Laurencia had been incorrectly identified and their true identity has been determined. A key to the Ceylon species of Laurencia is given.

Diterpenes, sesquiterpenes, and a C-15-acetogenin from the marine red alga Laurencia mariannensis

In addition to 10 known compounds (7-16), one new brominated diterpene, 10-hydroxykahukuene B (1), two new sesquiterpenes, 9-deoxyelatol (2) and isodactyloxene A (3), one new brominated C-15-acetogenin, laurenmariallene (4), and two new naturally occurring halogenated sesquiterpenes (5 and 6) that were previously obtained as intemediates in a biomimetic synthetic study of rhodolaureol and rhodolauradiol have been isolated and identified from the organic extract of the marine red alga Laurencia mariannensis. The structures of these compounds were established by spectroscopic methods. The antibacterial and antifungal activities of new compounds 1-4 were evaluated.

Laurendecumallenes A-B and laurendecumenynes A-B, halogenated nonterpenoid C-15-Acetogenins from the marine red alga Laurencia decumbens

Four new halogenated nonterpenoid C-15-acetogenins, 4:7,6:13-bisepoxy-9,10-diol-1,12-dibromopentadeca-1,2-diene (1, laurendecumallene A), 4:7,6:12-bisepoxy-9,10-diol-1,13-dibromopentadeca-1,2-diene (2, laurendecumallene 13), (3Z)-6:10,7:13-bisepoxy-12-bromo-9-hydroperoxylpentadeca-3-en-1-yne (3, laurendecumenyne A), and (3Z)-6:10,9:13-bisepoxy-12-bromo-7-chloropentadeca-3-en-1-yne (4, laurendecumenyne 13), together with one known halogenated C-15-acetogenin elatenyne (5) were isolated and identified from the organic extract of the marine red alga Laurencia decumbens. Their structures and relative stereochemistry were established by means of spectroscopic analysis including UV, IR, high-resolution electrospray ionization mass spectrometry (HRESIMS), and ID and 2D NMR techniques. All these metabolites were submitted for the cytotoxic assay against tumor cell line A549 (human lung adenocarcinoma), but all of them were found inactive (IC50 > 10 mu g/mL).

Halogenated Terpenes and a C-15-Acetogenin from the Marine Red Alga Laurencia saitoi

Seven parguerane diterpenes: 15-bromo-2,7,19-triacetoxyparguer-9(11)-en-16-ol (1), 15-bromo-2,7,16,19-tetraacetoxyparguer-9(11)-ene (2), 15-bromo-2,19-diacetoxyparguer-9(11)-en-7,16-diol (3), 15-bromo-2,16,19-triacetoxyparguer-9(11)-en-7-ol (4), 15bromo-2,16-diacetoxyparguer-9(11)-en-7-ol (5), 15-bromoparguer-9(11)-en-16-ol (6), 15-bromoparguer-7-en-16-ol (7), two polyether triterpenes: thyrsiferol (8) and thyrsiferyl 23-acetate (9), and one C15-acetogenin, neolaurallene (10), were isolated from a sample of marine red alga Laurencia saitoi collected off the coast of Yantai. Their structures were established by detailed NMR spectroscopic analysis and comparison with literature data.

Halogenated Sesquiterpenes from the Marine Red Alga Laurencia saitoi (Rhodomelaceae)

Four new halogenated sesquiterpenes, 10-bromo-3-chloro-2,7-epoxychamigr-9-en-8a-of (1), 2,10 beta-dibromochamigra-2,7-dien-9 alpha-ol (2), (9S)-2-bromo-3-chloro-6,9-epoxybisabola-7(14),10-diene (3), and (9R)-2-bromo-3-chloro-6,9-epoxybisabola-7(14),10-diene (4), were characterized from the marine red alga Laurencia saitoi. In addition, two known halosesquiterpenes, 2,10-dibromo-3-chlorochamigr-7-en-9 alpha-ol (5) and isolaurenisol (6), were also isolated and identified. Their structures were established on the basis of extensive analysis of spectroscopic data.

A new rearranged chamigrane sesquiterpene from Laurencia okamurai

A new rearranged chamigrane sesquiterpene, named laurenokamurin, was isolated from the marine red alga Laurencia okamurai. Its structure was determined on the basis of spectroscopic methods. (C) 2008 Bin Gui Wang. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

Two new aristolane sesquiterpenes from Laurencia similis

Two new aristolane sesquiterpenes, namely, aristolan-10-ol-9-one and aristolan-8-en-1-one, were isolated from the red alga Laurencia similis. Their structures were established on the basis of various NMR spectroscopic analyses, including 2D NMR techniques (H-1-H-1 COSY, HMQC, HMBC, and NOESY) and HR-FAB-MS. (c) 2007 Bin Gui Wang. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

Two new brominated diterpenes from Laurencia decumbens

Two new brominated diterpenes, namely, laurendecumtriol and 11-deacetylpinnaterpene C, were isolated and identified from the marine red alga Laurencia decumbens. Their structures were established on the basis of various NMR spectroscopic techniques and HR-ESI-MS analyses. (c) 2007 Bing Gui Wang. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

Laurenidificin, a new brominated C-15-acetogenin from the marine red alga Laurencia nidifica

new brominated C-15-acetogenin, namely, laurenidificin, was isolated from the marine red alga Laurencia nidifica. Its structure was determined on the basis of spectroscopic methods. (C) 2010 Bin Gui Wang. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

Aristolane sesquiterpenes and highly brominated indoles from the marine red alga Laurencia similis (Rhodomelaceae)

Three new polybrominated 1H-indoles, compounds 1-3, and three new aristolane sesquiterpenes, compounds 4-6, were isolated from the marine red alga Laurencia similis, together with seven known natural products. Their structures were elucidated on the basis of detailed spectroscopic and mass-spectrometric analyses, as well as by comparison with literature data.

Highly Oxygenated Triterpenoids from the Marine Red Alga Laurencia mariannensis (Rhodomelaceae)

Two new and one known squalenoid-derived triterpenoids. namely, laurenmariannol (1) and (21 alpha)-21-hydroxythyrsiferol (2). and the known thyrsiferol (3) were isolated and identified from the marine red alga Laurencia mariannensis, which was collected off the coast of Hainan and Weizhou Islands of China. The structures of these compounds were established by means of spectroscopic analyses, as well as by comparison with literature data. Compounds I and 2 displayed significant cytotoxic activity against P-388 tumor cells with IC50 values of 0.6 and 6.6 mu g/ml, respectively.

Terpenes and polybromoindoles from the marine red alga Laurencia decumbens (Rhodomelaceae)

Two new brominated diterpenes, namely, laurendecumtriol (1) and 11-O-deacetylpinnaterpene C (2), one new polybromoindole, 2,3,4,6-tetrabromo-1-methyl-1H-indole (7), and six known natural products were isolated and identified from the marine red alga Laurencia decumbens. Their structures were elucidated on the basis of detailed spectroscopic and mass-spectrometric analysis as well as by comparison with literature data. Based on 2D-NMR experiments, the previously reported NMR data for pinnaterpene C (3) were reassigned.

Laurencia nanhaiense sp nov., a new species of the genus Laurencia(Rhodomelaceae, Rhodophyta) from China

Laurencia nanhaiense sp. nov. (Rhodomelaceae, Rhodophyta) is described from Hainan and Guangdong Provinces, China. The new species clearly displays one of the defining features of the genus, viz. four periaxial cells per vegetative axial segment. It differs from other closely related species in having a combination of features such as terete axes from a basal system composed of a primary, discoid holdfast and a secondary attachment to give rise to many short rhizoids, branching oppositely and alternately, irregularly tristichous or subverticillately polystichous, having more curve branches with very sparse, adventitious ultimate branchlets, non-projecting superficial cortical cells at the apices of ultimate branchlets, presence of longitudinally oriented secondary pit-connections between contiguous superficial cortical cells, absence of lenticular thickenings in the walls of medullary cells, parallel arrangement of tetrasporangia along the axis of stichidia, and presence of intercellular spaces between medullary cells.