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Four new 5-hydroxyanthranilic acid related compounds, named anthocidins A⁻D ( 1 ⁻ 4 ), two known analogues n -lauryl 5-hydroxyanthranilate ( 5 ) and isolauryl 5-hydroxyanthranilate ( 6 ), together with benzamide ( 7 ), 3-hydroxy-4-methoxycinnamamide ( 8 ), and (3 S - cis )-hexahydro-3-[(3,4-dihydroxyphenyl)methyl]pyrrolo[1,2- a ]pyrazine-1,4-dione ( 9 ), were isolated from the fermentation broth of the marine-derived actinomycete, Streptomyces sp. HDa1, which was isolated from the gut of a sea urchin, Anthocidaris crassispina , collected from Hainan Island, China. The structures of these secondary metabolites were elucidated on the basis of their 1D and 2D-NMR and mass spectroscopic data, and anthocidin A was confirmed by single-crystal X-ray diffraction with Cu Kα radiation. Anthocidins A⁻D ( 1 ⁻ 4 ) feature an acetyl group substitution at the amino group and varying alkyl side chains at the carboxyl group of 5-hydroxyanthranilic acid, and compound 5 was isolated as a natural product for the first time. The cytotoxic and antibacterial activity of compounds 1 ⁻ 9 were evaluated., Competing Interests: The authors declare no conflict of interest.

Marine fungi are a promising source of novel bioactive natural products with diverse structure. In our search for new bioactive natural products from marine fungi, three new phenone derivatives, asperphenone A-C ( 1 - 3 ), have been isolated from the ethyl acetate extract of the fermentation broth of the mangrove-derived fungus, Aspergillus sp. YHZ-1. The chemical structures of these natural products were elucidated on the basis of mass spectrometry, one- and two-dimensional NMR spectroscopic analysis and asperphenone A and B were confirmed by single-crystal X-ray crystallography. Compounds 1 and 2 exhibited weak antibacterial activity against four Gram-positive bacteria, Staphylococcus aureus CMCC(B) 26003, Streptococcus pyogenes ATCC19615, Bacillus subtilis CICC 10283 and Micrococcus luteus , with the MIC values higher than 32.0 µM., Competing Interests: The authors declare no conflict of interest.

Six new furan derivatives, named 5-(3-methoxy-3-oxopropyl)-furan-2-carboxylic acid ( 1 ), 1-(5-(2-hydroxypropanoyl)-furan-2-yl)-pentan-3-one ( 2 ), 2-hydroxy-1-(5-(1-hydroxypentyl)-furan-2-yl)-propan-1-one ( 3 ), 1-(5-(1,2-dihydroxypropyl)-furan-2-yl)-pentan-1-one ( 4 ), 5-(1-hydroxypent-4-en-1-yl)-furan-2-carboxylic acid ( 5 ) and 5-(3-hydroxypentyl)-furan-2-carboxylic acid ( 6 ), together with two new natural products, named 5-(1-hydroxypentyl)-furan-2-carboxylic acid ( 7 ) and ( E )-5-(2-carboxyvinyl)-furan-2-carboxylic acid ( 8 ), were isolated from the solid rice fermentation of endophytic fungus Coriolopsis sp. J5, which was derived from mangrove plant Ceriops tagal . Their structures were unambiguously elucidated based on 1D and 2D NMR spectroscopy, and by HRESIMS measurements, as well as by comparison with the literature.

Four new mexicanolide-type limonoids 1-4, along with two known limonoids 5-6, were isolated from the ethanolic extracts of roots of the Traditional Chinese Medicine Trichilia sinensis. Their structures were unambiguously determined by analysis of spectroscopic data, including 1D and 2D NMR as well as MS, and by comparison with literature data. In addition, the acetylcholinesterase (AChE) inhibitory activity of compounds 1-6 was evaluated by the Ellman method. All these compounds showed weak AChE inhibitory activity, with the inhibition percentages ranging from 18.5% to 27.8%.

Two new sesquiterpenoids with guaiane skeletons-holosericin A (1) and holosericin B (2)-were isolated from the medicinal plant Daphne holosericea (Diels) Hamawa (Thymelaeceae). Their structures were elucidated by 1D and 2D-NMR spectroscopy, as well as HR-ESI-MS data. Compounds 1 and 2 were evaluated for inhibitory activities against acetylcholinesterase and compound 2 showed a moderate activity with 31% inhibition.

Agarwood is the fragrant resinous heartwood obtained from certain trees in the genus Aquilaria belonging to the family Thymelaeaceae. 2-(2-Phenylethyl)chromones and characteristic sesquiterpenes are the main classes of aromatic compounds isolated from agarwood. Although there are many sesquiterpenes, relatively few 2-(2-phenylethyl)chromones have been determined in agarwood by GC-MS. After analysis of the MS spectra of eighteen 2-(2-phenylethyl)chromone derivatives isolated from agarwood and identified by NMR spectroscopy, together with the reported MS data and characteristic of structures of 2-(2-phenylethyl)chromones, the MS characterization, fragmentation patterns and characteristic fragment peaks for the compounds were deduced and a table summarizing MS characterization of 2-(2-phenylethyl)chromones in agarwood is presented. All the 2-(2-phenylethyl)chromones previously reported in agarwood are substituted by methoxy or/and hydroxy groups, except for one compound. Due to the fact they all possess the same basic skeleton (molecular weight: 250) and similar substituent groups (methoxy or hydroxy groups), a formula (30m + 16n = MW - 250) is provided to calculate the number of methoxy (m) or hydroxy (n) groups according to molecular ion peak or molecular weight (MW). We deduced that the characteristic fragmentation behaviors of the 2-(2-phenylethyl)chromones are the cleavages of the CH₂-CH₂ bond between chromone moiety and phenyl moiety. Thus, characteristic fragment ions, such as m/z 91 [C₇H₇], 107 [C₇H₆+OH], 121 [C₇H₆+OCH₃], 137 [C₇H5+OH+OCH₃] are formed by different substituted benzyl moieties, while characteristic fragment ions such as m/z 160 [C₁₀H₈O₂], 176 [C₁₀H₇O₂+OH], 190 [C₁₀H₇O₂+OCH₃], 220 [C₁₀H₆O₂+OCH₃×2] are formed by different substituted chromone moieties. Furthermore, rules regarding to the relationship between the positions of hydroxy or methoxy groups and the relative abundances of benzyl and chromone fragment ions have been deduced. Elucidation of how the positions of hydroxy or methoxy groups affect the relative abundances of benzyl and chromone fragment peaks is also provided. Fifteen unidentified compounds of an artificial agarwood sample analyzed by GC-MS, were preliminary determined as 2-(2-phenylethyl)chromones by analysis of their MS characterization and by comparison of their MS spectra with those of 18 standard compounds or 2-(2-phenylethyl)chromones reported in literature according to the above-mentioned methods and rules. This report will be helpful for the analysis and structural elucidation of 2-(2-phenylethyl)chromones in agarwood by GC-MS, and provides fast and reliable characterization of the quality of agarwood.