Liangxiong Xu

β-Resorcylic Acid Lactones from a Paecilomyces Fungus

Six new beta-resorcylic acid lactones (1-6), named paecilomycins A-F, and five known compounds, aigilomycin B (7), zeaenol (8), aigialomycin D (9), aigialomycin F (10), and aigialospirol, were isolated from the mycelial solid culture of Paecilomyces sp. SC0924. Their structures were elucidated by extensive NMR analysis, single-crystal X-ray study, and chemical correlations. Compounds 5 and 10 exhibited antiplasmodial activity against Plasmodium falciparum line 3D7 with IC(50) values of 20.0 and 10.9 nM, respectively, and compounds 5-7 showed moderate activity against the P. falciparum line Dd2.

Three New Isochromans from the Mycelial Culture of a Cylindrocarpon Fungus

Three new isochroman derivatives, l-acetonyl-7-carboxyl-6,8-dihydroxy-3,4,5-trimethylisochroman (1), 7-carboxyl-6,8-dihydroxy-1,1,3,4,5-pentamethylisochroman (2), and 6,8-dihydroxy-3,4,5-trimethylisochroman (3), together with decarboxydihydrocitrinone (4), were isolated from mycelial solid culture of a Cylindrocarpon fungus. Their structures were established by spectroscopic methods.

Bioactive Polycyclic Tetramate Macrolactams from Lysobacter enzymogenes and Their Absolute Configurations by Theoretical ECD Calculations.

Two new polycyclic tetramate macrolactams, lysobacteramides A (1) and B (2), together with HSAF (heat-stable antifungal factor, 3), 3-dehydroxy HSAF (4), and alteramide A (5) were isolated from a culture of Lysobacter enzymogenes C3 in nutrient yeast glycerol medium. Their structures were determined by MS and extensive NMR analysis. The absolute configurations of 1-5 were assigned by theoretical calculations of their ECD spectra. Although HSAF and analogues were reported from several microorganisms, their absolute configurations had not been established. The isolation and the absolute configurations of these compounds revealed new insights into the biosynthetic mechanism for formation of the polycycles. Compounds 1-4 exhibited cytotoxic activity against human carcinoma A549, HepG2, and MCF-7 cells with IC50 values ranging from 0.26 to 10.3 μM. Compounds 2 and 3 showed antifungal activity against Fusarium verticillioides with IC50 value of 47.9 and 6.90 μg/mL, respectively.

Penicillitone, a Potent in Vitro Anti-inflammatory and Cytotoxic Rearranged Sterol with an Unusual Tetracycle Core Produced by Penicillium purpurogenum

A rearranged sterol with an unusual tetracycle core skeleton, penicillitone (1), and a new sterol, penicillisterol (2), were obtained from the culture of the fungus Penicillium purpurogenum SC0070. Their structures were characterized by spectroscopic analysis, DFT/TDDFT compuations, and X-ray diffraction. Compound 1 demonstrated potent inhibitory effects on tumor cell growth and key pro-inflammatory cytokine production in macrophages. A biogenetic pathway with oxidative cleavage and vinylogous aldol addition as key reactions is proposed for 1.

Polyoxygenated methyl cyclohexanoids from a terrestrial ampelomyces fungus.

Seven structurally related new polyoxygenated methyl cyclohexanoids, ampelomins A-G (1-7), were isolated from the mycelial solid culture of a soil-derived Ampelomyces fungus. Their structures were determined by spectroscopic and chemical means. Ampelomins A (1), C (3), E (5), and G (7) exhibited weak activity against alpha-glucosidase with IC(50) values of 1.74-5.93 mM, and ampelomin A (1) showed moderate antibacterial activity with MIC(90) values ranging from 202.4 to 1015.9 microM. A plausible polyketide biogenetic pathway is postulated for these compounds.

Antifungal Activity of Hypothemycin against Peronophythora Litchii In Vitro And In Vivo

The antifungal activity of a natural resorcylic acid lactone, hypothemycin (HPM), against Peronophythora litchii in vitro and in vivo was investigated. HPM treatment substantially suppressed spore germination of P. litchi, with the inhibition rate of 100% when 0.78 μg/mL HPM was applied. Similarly, mycelial growth of P. litchii was efficiently inhibited. Furthermore, HPM caused the ultrastructural modifications of P. litchii, including the disruption of the cell wall and the endomembrane system, especially the plasma membrane, mitochondria, and vacuoles, which led to the destruction of the cellular integrity. Moreover, application of HPM significantly reduced decay and suppressed peel browning of postharvest litchi fruit inoculated with P. litchii during storage at 28 °C. Overall, these findings suggested that HPM exhibited excellent antifungal activity against P. litchii both in vitro and in vivo, which could be helpful for the storage of harvest litchi fruit.

Bioactive dammarane-type saponins from Operculina turpethum.

Four new dammarane-type saponins, operculinosides A-D (1-4), were isolated from the aerial parts of Operculina turpethum, of which 1 and 2 are the first two dammarane-type triterpenoids having an oxymethyl group at C-24. Their structures were determined by spectroscopic analysis and acid hydrolysis. The absolute configuration of operculinoside A (1) was confirmed by X-ray crystallography. Compounds 1 and 3 showed significant protective activities against d-galactosamine-induced toxicity in L-02 human hepatic cells.

A novel cyclopropyl-containing fatty acid glucoside from the seeds of Litchi chinensis

3,12-Dihydroxy-cis-3,4-methylenedodecanoic acid 3-O-β-d-glucopyranoside, trivially named litchioside C (1), the first cyclopropyl-containing fatty acid glycoside, was isolated along with three previously uncharacterized galactosylacylglycerols from the seeds of Litchi chinensis. Its structure was established on the basis of spectroscopic analysis including HRESIMS and 2D NMR spectra. Its antioxidant and antibacterial activities were evaluated and its biogenetic pathway was discussed.

Cyclopeptides from Amanita exitialis

A new cyclic nonapeptide, amanexitide (1), along with the known cyclopeptides, α- and β-amanitins, was isolated from the fruiting bodies of Amanita exitialis, a newly described poisonous mushroom endemic to Guangzhou, Guangdong Province, China. Its amino acid composition and absolute configuration were determined by chemical degradation and derivatization followed by chiral GC analysis. Its amino acid sequence was elucidated by extensive analysis of ESIMS/MS and FTICRMS data. The occurrence of 1 in this mushroom is interesting because it has a structure closely related to antamanide, a cyclic decapeptide with antidote activity against amatoxins and phallotoxins, occurring in A. phalloides.

Anti-inflammatory cyclopeptides from exocarps of sugar-apples

Two new cyclic peptides, fanlizhicyclopeptide A, cyclo(Pro(1)-Pro(2)-Tyr(3)-Leu(4)-Pro(5)-Gly(6)-Val(7)) (1), and fanlizhicyclopeptide B, cyclo(Pro(1)-Ile(2)-Tyr(3)-Ala(4)-Gly(5)) (2), were isolated along with six known kaurane diterpenoids and a known clovane sesquiterpene from the exocarps of sugar-apples, the fruit of Annona squamosa. Their structures were elucidated by ESI MS/MS experiments, 1D and 2D NMR data and chemical degradation. In the anti-inflammatory assay, both 1 and 2 showed in vitro inhibitory effects on the production of pro-inflammatory cytokines, TNF-α and IL-6, in LPS-stimulated RAW 264.7 macrophages.