Chemical and Biological Study of Novel Aplysiatoxin Derivatives from the Marine Cyanobacterium Lyngbya sp.

Since 1970s, aplysiatoxins (ATXs), a class of biologically active dermatoxins, were identified from the marine mollusk Stylocheilus longicauda, whilst further research indicated that ATXs were originally metabolized by cyanobacteria. So far, there have been 45 aplysiatoxin derivatives discovered from marine cyanobacteria with various geographies. Recently, we isolated two neo-debromoaplysiatoxins, neo-debromoaplysiatoxin G (1) and neo-debromoaplysiatoxin H (2) from the cyanobacterium Lyngbya sp. collected from the South China Sea. The freeze-dried cyanobacterium was extracted with liquid–liquid extraction of organic solvents, and then was subjected to multiple chromatographies to yield neo-debromoaplysiatoxin G (1) (3.6 mg) and neo-debromoaplysiatoxin H (2) (4.3 mg). They were elucidated with spectroscopic methods. Moreover, the brine shrimp toxicity of the aplysiatoxin derivatives representing differential structural classifications indicated that the debromoaplysiatoxin was the most toxic compound (half inhibitory concentration (IC50) value = 0.34 ± 0.036 µM). While neo-aplysiatoxins (neo-ATXs) did not exhibit apparent brine shrimp toxicity, but showed potent blocking action against potassium channel Kv1.5, likewise, compounds 1 and 2 with IC50 values of 1.79 ± 0.22 µM and 1.46 ± 0.14 µM, respectively. Therefore, much of the current knowledge suggests the ATXs with different structure modifications may modulate multiple cellular signaling processes in animal systems leading to the harmful effects on public health.

Green-Synthesized FeSO4 Nanoparticles Exhibit Antibacterial and Cytotoxic Activity by DNA Degradation

Objective: The current study reports a green, rapid and one-pot synthesis of FeSO4 nanoparticles using Hibiscus rosasinensis floral extract as a reducing and capping agent. 0.5M of FeSO4 was stirred with the floral extract of H. rosasinensis for around 20 minutes at 37ºC and pH 7. Methods: The development of pink color was considered as the endpoint of reduction and the nanoparticles were characterized by UV-Vis spectrum, EDAX, DLS, FTIR, FESEM, and XRD. UV-Vis spectral analysis indicated a peak at 530 nm and EDAX measurement revealed the presence of Fe, S, O and C elements in the nanoparticle sample. The FTIR analysis showed amines, alcohol and alkene groups that act as capping agents for the produced nanoparticles. FESEM and XRD determination presented FeSO4 nanoparticles of 40-60 nm in size. The synthesized nanoparticles were found to have antibacterial activity against 6 pathogenic bacteria with MIC and MBC of 40 mg/mL. Results: To determine the toxicity at the eukaryotic level, brine shrimp toxicity assay was conducted and 100% mortality was found at concentrations >0.06 mg/mL. Gel shift assay suggested the mechanism of toxicity of FeSO4 NPs by binding and degradation of DNA molecules. Conclusion: From the results, the authors demonstrate the ease of green synthesis of FeSO4 nanoparticles and its bioactivity that may have potential applications as drugs and drug delivery systems against various diseases.

Brine Shrimp Toxicity of Essential Oils from Musa spp.

Essential oils of seven Musa spp.’s fruits namely, Musa acuminata colla ‘gros michel’ (PE), Musa acuminata colla ‘lakatan’ (PB), Musa acuminata colla ‘sucrier’ (PM), Musa acuminata × balbisiana ‘horn plantain’ (PT), Musa acuminata × balbisiana colla ‘saba’ (PN), Musa acuminata colla 'inarnibal' (PO) and Musa acuminata colla ‘red’ (PJ) were extracted by hydrodistillation method using Clevenger apparatus. The essential oils were analysed using GC-FID and identified using Kovat Indeces compared with published information. PE gave the highest yields of oils compared to the other species with yield of 0.43% and 0.28% for its peels and flesh, respectively. The most abundant groups present in most of the essential oils are ester and alcohol groups. The brine shrimp toxicity of PT, PM, PN and PO essential oils were tested and showed toxicity against brine shrimp in dose dependent manner. It can be concluded that the essential oils showed some biological activities which may be a potent medicine in curing tumor. This study implies that the presence of ester and alcohol groups are a good marker for the biological activities of plants. Further studies should focus on the potential of the essential oils of Musa spp. as an antitumor medicine.