A SARS-coronovirus 3CL protease inhibitor isolated from the marine sponge Axinella cf. corrugata: structure elucidation and synthesis

Abstract

Dois derivados cumarínicos, o ester metílico do ácido 4-esculetinocarboxílico (1) e o éster etílico do ácido 4-esculetinocarboxílico (2), foram isolados da esponja marinha Axinella cf. corrugata. A determinação estrutural dos compostos isolados foi realizada pela análise de seus dados espectroscópicos e pela síntese do composto 2. Estes são os primeiros derivados cumarínicos isolados de uma esponja marinha. O éster etílico 2 apresentou atividade in vitro contra a SARS 3Cl-protease e de inibição de células Vero infectadas com o SARS coronavírus, em concentrações que não provocaram citotoxicidade.Two coumarin derivatives, esculetin-4-carboxylic acid methyl ester (1) and esculetin-4-carboxylic acid ethyl ester (2), have been isolated from the marine sponge Axinella cf. corrugata. Structure determination included analysis of spectroscopic data and total synthesis of compound 2. These are the first coumarin derivatives isolated from a marine sponge. The ethyl ester 2 was found to be an in vitro inhibitor of SARS 3CL-protease and an effective inhibitor of SARS-CoV replication in Vero cells at non-cytotoxic concentrations.Keywords: esculetin, marine sponge, Axinella cf. corrugata, SARS, anti-viral IntroductionIn 2002 and 2003, several cases of a life-threatening respiratory disease that was ultimately named "severe acute respiratory syndrome" (SARS) were reported from Guangdong Province in mainland China, Hong Kong, Canada, and Vietnam.1 The etiological agent responsible for SARS was quickly found to be a novel coronavirus (SARS-CoV). Among the viral gene products are several large polyproteins that must be proteolytically processed to generate the individual proteins required for viral replication to occur. Two viral proteases, PL2 pro and 3CL pro , are involved in degrading the large polyproteins. 2The viral protease 3CL pro is considered the most important of the two because it is responsible for the release of the key replicative proteins of the vírus, including the viral RNA polymerase and helicase proteins. The central role of 3CL pro in SARS-CoV replication has made it a high profile target for developing antiviral drugs to treat SARS.2 Recently, a novel fluorescence resonance energy transfer (FRET)-based assay to screen for 3CL pro inhibitors has been developed in one of our laboratories.3 As part of a screening of crude marine sponge extracts and pure compounds isolated from the marine sponges using this assay, we have found that the new natural product esculetin-4-carboxylic acid ethyl ester (2) isolated from Axinella cf. corrugata collected in Brazil is a an effective inhibitor of 3CL pro in vitro. 441 Lira et al. Vol. 18, No. 2, 2007 In our current search for new biologically active marine natural products, 4,5 we decided to investigate the MeOH crude extract of the sponge Axinella cf. corrugata, which displayed cytotoxic activity against breast MCF-7 and colon B16 cancer cell lines. Although the cytotoxic activity was lost during the crude extract fractionation, photodiode array detection-HPLC analysi...

Coumarins — An Important Class of Phytochemicals

“…Originally, coumarin was isolated from the seed of D. odorata. Coumarins are secondary metabolites of higher plants, few microorganisms (bacteria and fungi), and sponges [45]. The function of this type of end product of secondary metabolism is related to defense mechanisms against herbivores and attacks by microorganisms.…”

Marine pharmacology in 2007–8: Marine compounds with antibacterial, anticoagulant, antifungal, anti-inflammatory, antimalarial, antiprotozoal, antituberculosis, and antiviral activities; affecting the immune and nervous system, and other miscellaneous mechanisms of action

“…As shown in Table 1, three reports were published on the antiviral pharmacology of novel marine natural products against severe acute respiratory syndrome (SARS) Corona virus, herpes simplex, and dengue virus during 2007-8. de Lira et al (2007) discovered that the new esculetin-4-carboxylic acid ethyl ester (67) from the Brazilian marine sponge Axinella cf. corrugata inhibited the SARS 3CL protease (IC 50 =46 μM).…”

Activities and Novel Applications of Secondary Metabolite Coumarins

“…Coumarins have shown to be present in seeds, roots, stems, flowers, leaves, and fruits, although the highest concentrations are reported in flowers and fruits (Venugopala et al, 2013). Coumarin was also isolated from microorganisms and sponges (De Lira, 2007). They are produced from phenylalanine via shikimate biosynthesis (Dewick, 2002).…”