Halocynthia roretzi

A series of mycosporine-like amino-acids have been isolated from this ascidian 45 the newest (and seventh) is (40). 

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Nomura and Ogata provided the first evidence that tunicates can produce PGs [17]. Using a rat stomach fundus bioassay, Halocynthia roretzi tissues were shown to possess low levels of PGs. The testes showed higher levels (9 ngg-1 wet tissue) than ovary and muscle tissue. The sea-squirt Styela clava did not show PGs by this method. No structures were determined in this work. Reexamination of the ability of H, roretzi to produce PGs was carried out by Ogata and coworkers [19]. Incubation of selected tissues with 14C-labeled eicosa-8,11,14-trienoic acid and subsequent isolation of PGE and PGF fractions after addition of carrier showed the branchial tissue to have the highest conversion levels. Quantitation was done by LSC. Using a TLC radioscanner, the authors determined that fractions with metabolites similar to PGE and PGF... 

Kawahara H, Yokosawa H (1992) Cell cyde-dependent change of proteasome distribution during embryonic development of the ascidian Halocynthia roretzi. Dev Biol 151 27-33... 

Four simple sulfates (158-161) were identified as antimicrobial constituents of Halocynthia roretzi from Japan [160]. Sodium (or potassium) 2,6-dimethyIheptyl sulfate (161) was also found in Polycitor adriaticus from Croatia [161]. The absolute configuration of 2,6-dimethylheptyl sulfate (161), which has also been found in other Mediterranean ascidians, has been determined using Mosher s method [162],... 

The bromotyramine derivatives ceratinamide A (136) and psammaplysin A (137) from the sponge Pseudoceratina purpurea inhibit the settlement and metamorphosis of cyprid larvae of the barnacle Balanus amphitrite (ED50 0.10 and 0.27 (Jg/ml). Interestingly, psammaplysin A induces larval metamorphosis of the ascidian Halocynthia roretzi (ED 0o 1.2 (Jg/ml) [74]. 

Lumichrome (Figure 10.1), a water-soluble degradation product of riboflavin,157 appears to be the first characterized gregarious (produced by conspecifics) cue for induction of metamorphosis of a marine invertebrate. Lumichrome is exuded into aqueous media from cultures of larvae of the ascidian Halocynthia roretzi, and was also found in the eggs, gonads, and tunic of the adults following extraction in methanol.157 Metamorphosis of larvae was induced by purified lumichrome... 

Tsukamoto, S., Kato, H., Hirota, H., and Fusetani, N., Lumichrome a larval metamorphosis-inducing substance in the ascidian Halocynthia roretzi, Eur. J. Biochem., 264, 785, 1999. 

Many ascidians live gregariously, and for some of these species conspecific chemical cues may play an important role in gregarious settlement of the larvae. The extracts of conspecific adults, larvae, or their conditioned seawater have been shown to contain metamorphosis inducers which have never been characterized.74-75 Recently, Fusetani and co-workers elucidated the structure of the metamorphosis inducer for the solitary ascidian Halocynthia roretzi, which was isolated from seawater conditioned by ascidian larvae.10 The compound isolated from the medium was identical to lumichrome, a compound known to be a degradation product of riboflavin (Figure 13.1). The origin of lumichrome in //. roretzi is not known at present. 

Kobayashi, J., Nakamura, H., and Hirata, Y., Isolation and structure of a UV-absorbing substance 337 from the ascidian Halocynthia roretzi, Tetrahedron Lett., 22, 3001, 1981. 

Recent electron, X-ray and neutron diffraction work has established the structures for both cellulose and Ip. Microcrystalline samples were obtained by mild acid hydrolysis of the cellulose walls of the freshwater alga Glaucocystis nostochinearum and the tunicate Halocynthia roretzi and were... 

Wada, S., Katsuyama, Y., Sato, Y., Itoh, C., Saiga, H. 1996. Hroth an orthodenticle-related homeobox gene of the ascidian, Halocynthia roretzi its expression and putative roles in the axis formation during embryogenesis. Mech. Dev. 60, 59-71. 

Figure 9 Raman spectra of tunicate (Halocynthia roretzi) and Valonia macrophysa celluloses in the Raman active regions.

The synthesis of various C-26 sterols from cholic ester derivatives by appropriate Grignard reactions has been achieved. In particular, 3)5-hydroxy-24-dimethyl-5a-chol-23-ene (394), previously isolated from Halocynthia roretzi, has been prepared by this route. 

Related to the tunichromes are halocyamines A (41) and B (42) from Halocynthia roretzi. [39]. These are tetrapeptides which contain a Dopa residue (note the authors have depicted a D-Dopa residue in their structure). Both halocyamines displayed antimicrobial activity against B. subtilis (MIC 50pg /mL), B. megateruine (MIC 50 pg/mL), B. cereus (MIC 100 pg /mL) and the yeast Cryptococcus neoformans (MIC 100 pg /mL). Halocyamine A was also found to be cytotoxic to neuroblastoma N-18 cells at 160 pM for 24 hours. It caused degeneration of neurite and soma in cultured rat fetal brain cells at 100 pM and death of Hep-G2 cells at 200 pM for 24 hours. 

Isol. from the ascidian Halocynthia roretzi. Antibacterial and antifungal agent. 

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