Isocoumarin derivatives from the endophytic fungus, Pestalotiopsis sp.

Five new isocoumarin derivatives, pestalactone A-C (1-3) and pestapyrone D-E (4-5), together with two known compounds (6-7) were isolated from the solid cultures of the endophytic fungus Pestalotiopsis sp. obtained from Photinia frasery. Their structures were mainly determined by extensive spectroscopic analysis, Mo2(OCOCH3)4-induced electronic circular dichroism (ECD), and ECD calculation. Compounds 1 and 2 were rare isocoumarin derivatives and derived from distinctive polyketide pathways. Compound 3 exhibited potent antifungal activity against Candida glabrata (ATCC 90030) with an MIC50 value of 3.49±0.21µg/mL.

New phenalenone derivatives from Pinellia ternata tubers derived Aspergillus sp.

Nine new phenalenone derivatives (1-9), along with two known analogues (10-11) have been isolated from the solid cultures of an endophytic fungus Aspergillus sp. which was obtained from Pinellia ternate. Their structures were established through interpretations of spectroscopic evidence, and some of their absolute configurations were determined by electronic circular dichroism (ECD) and Mo2(OCOCH3)4 induced ECD. All of the phenalenones are unusual acyclic diterpenoid adducts, which are diversely oxidized and partly epoxidized to form different heterocycles. In addition, compound 10 exhibited significant antimicrobial activity against Pseudomonas aeruginosa, Staphylococcus aureus, and Bacillus subtilis with MIC50 values of 1.87, 2.77, and 4.80µg/mL, respectively.

In Vitro Antibiofilm Activity of Eucarobustol E against Candida albicans.

Formyl-phloroglucinol meroterpenoids (FPMs) are important types of natural products with various bioactivities. Our antifungal susceptibility assay showed that one of the Eucalyptus robusta-derived FPMs, eucarobustol E (EE), exerted a strong inhibitory effect against Candida albicans biofilms at a concentration of 16 µg/ml. EE was found to block the yeast-to-hypha transition and reduce the cellular surface hydrophobicity of the biofilm cells. RNA sequencing and real-time reverse transcription-PCR analysis showed that exposure to 16 µg/ml of EE resulted in marked reductions in the levels of expressions of genes involved in hyphal growth (EFG1, CPH1, TEC1, EED1, UME6, and HGC1) and cell surface protein genes (ALS3, HWP1, and SAP5). Interestingly, in response to EE, genes involved in ergosterol biosynthesis were downregulated, while the farnesol-encoding gene (DPP3) was upregulated, and these findings were in agreement with those from the quantification of ergosterol and farnesol. Combined with the obvious elevation of negative regulator genes (TUP1, NRG1), we speculated that EE's inhibition of carbon flow to ergosterol triggered the mechanisms of the negative regulation of hyphal growth and eventually led to biofilm inhibition.

Two new compounds from the green peel of Juglans mandshurica.

A new cyclic diarylheptanoid (1) and a new flavone glucoside (2), along with seven known compounds, were isolated from the green peel of Juglans mandshurica. Their structures were elucidated based on extensive spectroscopic analyses. Moreover, the cytotoxicity against NCI-H460, A549, and K562 cancer cells of compounds 1-6 was evaluated. The results showed that compound 3 exhibited moderate inhibitory potency against the growth of three cell lines.

Antimicrobial metabolites from the plant endophytic fungus Penicillium sp.

Five rare dichloro aromatic polyketides (1-5) were obtained from an endophytic fungus Penicillium sp., along with five known metabolites (6-10). Their structures were elucidated by extensive spectroscopic analysis, Mosher methods, as well as [Rh2(OCOCF3)4]-induced electronic circular dichroism (ECD) experiments. Compounds 2-4 and 6 structurally involved acyclic 1.3-diols, the uneasy configuration determinations of which were well carried out by double-derivation NMR methods. Compounds 1-10 were evaluated for their antibacterial and antifungal activities against five strains of human pathogenic microorganisms. Helvolic acid (7) showed potent inhibitory effects against Staphylococcus aureus and Pseudomonas aeruginosa with MIC (minimum inhibitory concentration) values of 5.8 and 4.6µg/mL, respectively.

1H NMR spectroscopy-guided isolation of new sucrose esters from Physalis alkekengi var. franchetii and their antibacterial activity.

Ten new sucrose esters, physakengoses A-J (1-10), were isolated from the aerial parts of Physalis alkekengi var. franchetii under the guidance of 1H NMR spectroscopy. Their structures were determined by spectroscopic analyses (HRESIMS, 1D and 2D NMR, and ESIMS) and chemical methods. These new compounds were tested for antibacterial activities against Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa and Escherichia coli. Among them, compounds 2 and 5-8 showed potent inhibitory effects against test strains with MIC values ranging from 3.5 to 14.9µg/mL. These findings may indicate that the P. alkekengi var. franchetii has potential application as an ingredient in pharmaceuticals.

New alkaloids from the leaves of Evodia rutaecarpa.

One new indole alkaloid (1) and one new indole alkaloidal glycoside (2), together with nine known alkaloids (3-11), were isolated from the leaves of Evodia rutaecarpa. Their structures were determined on the basis of spectroscopic and chemical methods. Compound 4 exhibited potent activity against Pseudomonas aeruginosa with an MIC value of 7.13 µg/ml.

Sarglaperoxides A and B, Sesquiterpene-Normonoterpene Conjugates with a Peroxide Bridge from the Seeds of Sarcandra glabra.

Sarglaperoxides A (1) and B (2), a pair of unusual sesquiterpene-normonoterpene conjugates with a peroxide bridge, were isolated from the seeds of Sarcandra glabra. The structures and absolute configurations of 1 and 2 were determined on the basis of spectroscopic data analysis, including MS, NMR, CD, and XRD. The two compounds were screened in antimicrobial, anti-inflammatory, and cytotoxic bioassays and showed moderate bioactivities.

Unciflavones A-F, six novel flavonoids from Selaginella uncinata (Desv.) Spring.

Six new flavonoids, unciflavones A-F (1-6), have been isolated from medicinal plant Selaginella uncinata (Desv.) Spring. Their structures were established on the basis of extensive NMR analysis including 1D NMR ((1)H, (13)C and DEPT) and 2D NMR (COSY, HSQC, HMBC) experiments as well as HRESIMS analysis. All compounds possess exceptional structural features with an aryl substituent at the C-8 position, which are uncommonly encountered in natural resources and firstly reported in genus Selaginella.