TAXONOMIC AND PHYTOCHEMCIAL STUDIES OF CERTAIN BROWN ALGAE FROM THE COAST OF KARACHI

Fourteen commonly occurring species of marine benthic algae i.e. Colpomenia sinuosa (Mertens ex Roth) Derbes et Solier, Dictyoperis austalis (Sonder)Askenasy, Dictyota dichotoma (Hudson) Lamouroux, D. dumosa Borgesen, D. hauckiana Nizamuddin, D. indica Sonder, D. maxima Zanardini, Hincksia mitchelliae (Harvey) Silva, Jolyna laminarioides Guimaraes in Guimeraes et al., Padina tetrastromatica Hauck, Sargassum tenerrimum J. Agardh, Spatoglossum variabile Figari et De Notaris, Stoechospennum marginatum (C. Agardh) Kutzing and Stokeyia indica Thivy et Doshi, belonging to all the three classes of Phaeophyta, have been collected from the coastal areas near Karachi (Pakistan) and investivated taxonomically as well as phycochemically. Although, all of them are taxonomically known species, but Dictyota dichotoma, D. dumosa, D. hauckiana, D. indica, D. maxima, Jolyna laminarioides. Padina tetrastromatica, Sargassum tenerrimum and Stokeyia indica have been described taxonomically for the first time from the coast of PakistanA variety of saturated and unsaturated fatty acids were detected in the extracts of these algal species and analysed as methyl esters qualitatively as well as quantitatively through GLC and GC-MS techniques. Several sterols, terpenes, polyols and certain metabolites have been isolated from those seaweeds, purified and their structures elucidated chemically through standard spectroscopic methods e.g. El-FAB-, FD-, GC- & HR-MS and IR, 1H- & 13C-NMR. Certain new and novel compounds have been isolated from them: e.g. dicdichane from Dictyota dichotoma; hauckiosterol from Dictyota hauckiana and Spatoglossum variabile; dictinol, dictindiol, dictintriol, amijiol and sargasterol from dictyota indica; Padinolide from Colpomernia sinuosa and Padina tetrastromatica; 19-acetoxy-5 ®, 15, 18, (R & S)- trihydroxy-spata-13, 16 (E)-diene from spatoglossum variabile and Stoechospermum marginatum; 5 ® 15, 18, (R & S), 19-tetrahydroxy-spata-13, 16 (E)-diene, 5 ®, 18-dihydroxy-spata-13, 16 (E)-diene and 5 ® 16-dihydroxy-spata-13, 17-diene from Stoechospermum marginatum; stigasta-5, 23-diene-3β-ol from Jolyna laminarioides; and loliolide and stokerine from Stockeyia indicaThe hauckiosterol among sterols, dictinol, dictindiol and dictintriol among diterpenes and Padinolide, dicdichane and stokerine among metabolites were the new compounds isolated for the first time from a natural source. All the natural products described, have been reported for the first time from the corresponding algal species. The four tricyclic diterpenoids isolated from Stochospermum marginatum have also been tested against three gram positive and six gram negative bacteria as well as six pathogenic fungi, and were found to exhibit strong antimicrobial activity