Ciguatera fish poisoning (CFP) is a type of food poisoning caused by the consumption of a variety of toxic ciguatera fish species in the tropical and subtropical waters. Although there have been a large number of suspected CFP cases in the Southeast Asian countries, few were confirmed with causative ciguatoxins (CTXs), and reliable information on the symptoms still remains rather limited. In the present study, CTXs in red snapper Lutjanus bohar, implicated in two suspected CFP cases in Vietnam in 2014 and 2016, were determined by use of the single-quadrupole selected ion monitoring (SIM) liquid chromatography/mass spectrometry (LC/MS). Ciguatoxin-1B (CTX-1B), 54-deoxyCTX-1B, and 52-epi-54-deoxyCTX-1B were detected in the red snapper by our LC/MS method. Moreover, CTX-1B, 54-deoxyCTX-1B, and 52-epi-54-deoxyCTX-1B were further identified by the time of flight (TOF) LC/MS with the exact mass spectrum. The CTX profile of the red snapper in Vietnam is similar to those of ciguatera fish from Australia, Okinawa Islands in Japan, Kiribati, and Hong Kong. This is the first comprehensive report unambiguously identifying the causative toxins in fish implicated with reliable information on the poisoning symptoms in CFP in Vietnam and/or Southeast Asian countries.

This study aimed to document the seasonal cycle of steroid levels in the plasma and ovary, including testosterone (T), estradiol-17β (E₂) and 17α, 20β-dihydroxy-4-pregnen-3-one (DHP) in relation to ovarian development in wild populations of female blue tang fish. The gonadosomatic index (GSI%) maintained high values from April to July and increased from the II to IV ovarian stages and dropped in the V stage. Levels of plasma, ovary T and E₂ and DHP were high from March to July. Plasma T and E₂ levels were low in the II stage when most oocytes were previtellogenic, reaching a peak during spawning, and decreased in the V stages when fish were going to late spawning and termination. DHP was detected in all stages of the ovary with a higher level in spawning fish but decreased after spawning. These results revealed that T, E₂ and DHP could be involved in ovarian development and DHP may play a significant role as a maturational inducing hormone in blue tang fish.

In the coastal countries of Southeast Asia, fish is a staple diet and certain fish species are food delicacies to local populations or commercially important to individual communities. Although there have been several suspected cases of ciguatera fish poisoning (CFP) in Southeast Asian countries, few have been confirmed by ciguatoxins identification, resulting in limited information for the correct diagnosis of this food-borne disease. In the present study, ciguatoxin-1B (CTX-1B) in red snapper (Lutjanus bohar) implicated in a CFP case in Sabah, Malaysia, in December 2017 was determined by single-quadrupole selected ion monitoring (SIM) liquid chromatography/mass spectrometry (LC/MS). Continuous consumption of the toxic fish likely resulted in CFP, even when the toxin concentration in the fish consumed was low. The identification of the fish species was performed using the molecular characterization of the mitochondrial cytochrome c oxidase subunit I gene marker, with a phylogenetic analysis of the genus Lutjanus. This is the first report identifying the causative toxin in fish-implicated CFP in Malaysia.

This study investigates the sustainable extraction of nano-Hydroxyapatite (nano-HAp) from Lates calcarifer fish bones, a by-product of the seafood industry, through thermal calcination. Nano-HAp was synthesized at two temperatures (650 °C and 700 °C), resulting in rod-like (42 nm) and spherical (98 nm) particles, respectively. Both samples were identified as B-carbonated HAp, with Ca/P molar ratios of 1.842 for HAp 650-4 h and 1.856 for HAp 700-4 h, confirming the presence of B-type HAp, which has higher Ca/P ratios than the standard HAp found in bones and teeth (1.67). Cytotoxicity tests showed that both samples exceeded the ISO 10993-5:2009 standard, with L929 cell viability above 70% at concentrations up to 2 mg mL⁻¹. Notably, the study emphasizes that the size and morphology of nano-HAp play a critical role in its biological activity. Larger spherical particles (HAp 700-4 h) enhanced the proliferation of human bone marrow-derived mesenchymal stem cells (hBMSCs) more effectively than smaller rod-like particles (HAp 650-4 h), suggesting their greater potential for tissue engineering and bone regeneration applications. This work demonstrates the promising biocompatibility of fish bone-derived nano-HAp and its potential for sustainable biomedical applications.

On 5 November 2020, a poisoning event involving four people by the consumption of moray eel occurred in Khanh Hoa Province, Viet Nam, with signs indicative of ciguatera. The remaining moray portion was confiscated for identification of causative species and responsible toxins. The phylogenetic study based on COX1 identified the moray as Gymnothorax javanicus Bleeker (1859). Out of 17 marine lipophilic toxins (MLPs) that were analyzed using LC-MS/MS, only Pacific ciguatoxin-1 (P-CTX-1) was detected in the moray’s flesh at 1.30 ± 0.004 ng/g ww, while no toxin was found in the skin. The N2a assay’s ciguatoxicities in the skin and flesh were 0.69 ± 0.075 and 2.49 ± 0.216 ng P-CTX-1/g ww equivalent, respectively. In the N2a assay, the P-CTX-1 amount in the moray flesh was 1.9 times greater than that determined by LC-MS/MS, indicating the presence of additional sodium channel activators or a matrix effect. The P-CTX-1 amount in the moray flesh was at a level that generates major ciguatera poisoning (CP) symptoms in humans (1.0 ng/g P-CTX-1), makes sense given that four consumers experienced the onset of poisoning symptoms. This study is significant for the management of seafood safety since it is the first scientific report on the species and toxin in a moray causing ciguatera in Viet Nam.

Collagen extracted from the skin of fan-bellied leatherjacket was hydrolyzed and tested for antioxidant activity. The yields of acid soluble collagen (ASC) and pepsin soluble collagen (PSC) were 14.8% and 19.6%, respectively, based on the wet weight of skin. The SDS-PAGE results showed that collagen from the skin of this fish consists of α1 and α2 chains with molecular weight (MW) approximately 100 kDa, identified as type I collagen. Hydrolysis of collagen by the other enzymes, such as papain, bromelain, pepsin and alcalase could produce the peptides with MW less than 28 kDa. Hydrolyzed collagen possessed the antioxidant activity with different levels and greater than that of normal collagen.