Thirteen new metabolites, melophlins C-O (1-13), were identified from the marine sponge Melophlus sarassinorum. Compounds 1-13 represent tetramic acid derivatives that differ with regard to the nature of their alkyl side chains. The structures of the new compounds were elucidated on the basis of comprehensive spectral analysis (1H, 13C, 1H-1H COSY, HMQC, and HMBC NMR, as well as low- and high-resolution ESIMS and EIMS). The absolute configurations of 1, 8, 10, 11, 12, and 13 were determined by ESI LC/MS analysis of chiral derivatives obtained upon oxidation and hydrolysis of the respective parent compounds. Melophlin C (1) displayed pronounced antibacterial activity against Bacillus subtilisand Staphylococcus aureus, together with antifungal activity against Candida albicans.
Two new metabolites, microsphaerones A (1) and B (2), were identified from the EtOAc extract of the culture of an undescribed fungus of the genus Microsphaeropsis, isolated from the Mediterranean sponge Aplysina aerophoba. Compounds 1 and 2 represent the first examples of gamma-pyrone derivatives of the fungal genus Microsphaeropsis. The structures of the compounds were elucidated on the basis of comprehensive spectral analysis ((1)H, (13)C, (1)H-(1)H COSY, HMQC, and HMBC NMR, as well as low- and high-resolution ESI and EIMS experiments). The (S)-2-methylsuccinic acid moiety present in 1 was established by GC-MS analysis of a hydrolysis product.
Nesfatin-1 is a recently discovered metabolic peptide hormone that decreases food intake after lateral, third, or fourth brain ventricle; cisterna magna; or paraventricular nucleus (PVN) injection in ad libitum fed rats. Additional micro-injection studies will improve the understanding of how nesfatin-1 acts on the brain and define specific nuclei responsive to nesfatin-1, which will provide insight on its effects on food intake. We evaluated how nesfatin-1 injection into the dorsal vagal complex (DVC) modulates food intake response in rats during the dark phase. Consistent with previous observations, nesfatin-1-injected rats significantly reduced cumulative food intake over a 5-h period in rats. Chronic administration of nesfatin-1 into the DVC reduced body weight gain over a 10-day period. Because glucosensing neurons in the DVC are involved in glucoprivic feeding and homeostatic control of blood glucose, we examined the effect of nesfatin-1 on the excitability of DVC glucosensing neurons. Nesfatin-1 inhibited most of the glucose-inhibitory (GI) neurons and excited most of the glucose-excitatory (GE) neurons in the DVC. Current-clamp electrophysiology recordings from DVC glucosensing neurons in slice preparation showed that bath applied nesfatin-1(10 nM) increased the firing frequency of GE neurons and inhibited the firing rate of GI-neurons. Nesfatin-1 inhibited 88.9% (16/18) of gastric distension inhibitory (GD-INH) neurons and excited 76.2% (32/42) of gastric distension excitatory (GD-EXC) neurons. Thus, nesfatin-1 may control food intake by modulating the excitability of glucosensing neurons in the DVC.
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