2D NMR Studies of Bromotyrosine Alkaloid, Purpurealidin K from Marine Sponge Psammaplysilla purpurea

Abstract

Marine sponges of the order Verongida and related organisms are the richest source of bioactive bromotyrosine alkaloids. Purpurealidin K (1) along with purealidin Q (2), aerophobin 2 (3) and aplysamine 2 (4) were isolated from methanol extract of marine sponge Psammaplysilla purpurea collected from Madapam, Tamil Nadu, India. The structure of natural product, purpurealidin K (1) was assigned by extensive 1H, 13C, DEPT, TOCSY, HSQC & HMBC NMR experiments and electrospray ionization-quadrupole time-of-flight (ESI-QTOF MS/MS) mass spectrometric measurements. For the first time, the complete set of spectroscopic data of compound (1) has been obtained. Moreover, compounds (2-4) were identified by using various spectroscopic data and their comparison with literature reports. These bromotyrosine derived metabolites were evaluated against multiple drug resistance bacterial cells and against clinical pathogens, wherein purpurealidin K (1) displayed moderate activities against Methicillin Resistant Staphylococcus aureus (MRSA), Escherichia coli, Pseudomonas aeruginosa.