A New Diol Ester Derivative of Dinophysistoxin‐1 from Cultures of Prorocentrum lima Collected in South Korea

Abstract

Keywords: Prorocentrum lima, Dinophysistoxin-1, DTX-1 diol ester, Cytotoxicity Marine dinoflagellates have been widely studied because of their rich chemodiversity and biologically toxic compounds extracted from them. These organisms are considered the cause of most occurrences of food poisoning from seafood. 1-3 Among these, the genera Prorocentrum and Dinophysis were well known to produce diarrhetic shellfish poisoning (DSP) toxins such as the okadaic acid (OA), pectenotoxin-2 (PTX-2), and dinophysistoxin-1 (DTX-1), leading to disastrous influences on the shellfish industry worldwide due to their effect on human health. [4][5][6] Shellfish are believed to become toxic by accumulating the toxins through filterfeeding the algae of the two genera. Furthermore, many research works have also revealed the existence of a wide range of OA analogs from the large-scale cultivation or filter-feeding bivalve molluscs, such as scallops, clams, and mussels. The OA analogs are largely classified into 7-O-fatty acid esters, which are found only in shellfish, and diol esters, where the carboxylic group of OA is esterified with C 6 to C 10 diols. All of these constituents may be very important in the study of toxin production and toxin profile of shellfish or harmful algae in coast areas. [7][8][9] Recently, during the monitoring of toxic compounds from the benthic Prorocentrum lima spawned around Jeju island, Korea, an unidentified DTX-1 analog (1) was isolated from the toxic fractions of the cultures of P. lima and structurally characterized. This new compound is characterized by a lipid-soluble C 9 diol ester of DTX-1. As shown in Figure 1, most of the lipid-soluble diol esters previously reported in the literature are commonly derived from the OA parent compound. [10][11][12][13][14][15] Interestingly, on the other hand, 1 came from the DTX-1 compound. The 7-O-fatty acid esters of DTX-1, collectively named as DTX-3, have been found, 4 but, to our knowledge, diol esters of DTX-1, such as compound 1, have not been reported. In this paper, we present the cultivation method of P. lima, the characterization of compound 1, and its bioactivity.The methanolic extract of P. lima, exhibiting strong cytotoxicity during a brine shrimp lethality test, showed in the liquid chromatography-mass spectrometry (LC-MS) analysis the presence of two well-known DSP toxins: OA and DTX-1.Interestingly, a major peak in the LC-MS chromatogram was deduced to belong to a derivative of DTX-1 by its fragmented ion peak of m/z 841 in the MS/MS spectrum, which is identical to the mass value of the sodiated DTX-1. In order to isolate the corresponding compound, unialgal P. lima was cultivated up to a volume of 200 L. After harvesting the cultures by centrifugation, the cells were extracted using methanol, and the extract was chromatographed on a Sephadex LH20 column, yielding six fractions. Compound 1 was isolated and purified by reversed-phase HPLC from the mixture of the two fractions that are responsible for a strong cytotoxicity.Compound 1 was isolated a...

Relative Configurational Assignment of 4-Hydroxyprorocentrolide and Prorocentrolide C Isolated from a Benthic Dinoflagellate (Prorocentrum lima)

“…Benthic dinoflagellates of the Prorocentrum genus, found in temperate and tropical waters, are a source of diarrhetic shellfish poisoning (DSP) toxins, such as okadaic acid (OA), dinophysistoxin-1 (DTX-1), and their analogues. − In addition to DSP toxins, a variety of bioactive compounds have been isolated from cultured Prorocentrum species, e.g., prorocentrolides, , spiro-prorocentrimine, hoffmanniolide, prorocentrin, formosalides A and B, belizentrin, belizeanolide, prorocentrol, and limaol . Among these compounds, prorocentrolides and spiro-prorocentrimine are characterized by the presence of a cyclic imine (CI) group.…”

“…In particular, stererochemical studies on these compounds have not been reported, except for the partial determination of the relative configuration of prorocentrolide B . In the course of exploring cytotoxic compounds from P. lima cultures, we isolated cytotoxic OA, DTX-1, and OA/DTX-1 analogues and limaol. , Recently, two prorocentrolides, namely, 4-hydroxyprorocentrolide ( 1 ) and prorocentrolide C ( 2 ), were identified in the polar fractions of the same P. lima extract. Herein, we clarify the planar structures of these two compounds and determine the relative configurations of their stereocenters by spectroscopic techniques.…”

Limaol: A Polyketide from the Benthic Marine Dinoflagellate Prorocentrum lima

“…1,2 Prorocentrum is a representative genus that produces diarrhetic shellfish poisoning (DSP) toxins, such as okadaic acid (OA), dinophysistoxin-1 (DTX-1), and analogues. 3 Apart from these compounds, skeletally diverse bioactive compounds have also been isolated from cultured Prorocentrum species, including prorocentrolide, 4 spiro-prorocentrimine, 5 hoffmanniolide, 6 prorocentin, 7 formosalides A and B, 8 belizentrin, 9 belizeanolide, 10 and prorocentrol. 11 In our search for bioactive compounds from cultured P. lima, a new polyhydroxy compound, limaol (1), was isolated by cytotoxicity-guided fractionation.…”

“…Moreover, the orientations of H-20 and H-24 on this skeleton were determined to be equatorial and axial, respectively, from the coupling constants of the well-split neighboring proton signals: J = 2.7 Hz between H-20 and H-21 and J = 9.1 Hz between H-23 and H-24. Further ROESY correlations of H-17/H-19a, H-17/H-19b, and H-14/H-22 allowed determination of the relative orientation of the octahydropyrano[3,2-b]pyran and dihydropyran rings.On the other hand, the configurations of the stereogenic centers beyond C-25 were established by measurement of3 J HH values from the DQF-COSY and 2,3 J CH values from the HECADE spectra and observation of ROESY correlations. As shown in Figure3A, the coupling constants related with H-25, H-26a, and H-26b, in accordance with JBCA, determined the orientation of the two nonequivalent protons on C-26.…”

“…1 H and13 C NMR Data for Limaol (1) in CD 3 OD (500 MHz for 1 H, 125 MHz for 13 C) from 40% ACN + 60% H 2 O to 100% ACN for 40 min; flow rate: 1.8 mL/min) to yield a known OA-diol (MW = 928, 7.5 mg), a known DTX-1 derivative (MW = 956, 11.5 mg),3 and a mixture containing limaol (1, 3.2 mg). Following this separation, the mixture of 1 was purified by reversed-phase HPLC (column: Phenomenex Polar 250 × 4.6 mm; isocratic elution with 70% MeOH + 30% H 2 O + 0.1% formic acid; flow rate: 1 mL/min) to obtain limaol (1.6 mg).…”