Meroterpenoids from Rhododendron nivale / 中国中药杂志

To elucidate the chemical material basis of Rhododendron nivale, this study comprehensively used various chromatographic techniques to isolate and obtain five new meroterpenoid enantiomers(1a/1b-5a/5b) from the ethyl acetate extract of R. nivale. A variety of spectral analytical methods, such as high-resolution mass spectrometry(HRMS), nuclear magnetic resonance spectroscopy(NMR), and infrared(IR) spectrum, were used to evaluate the structure, combined with the measurement and calculation of electronic circular dichroism(ECD). The new compounds 1a/1b-4a/4b were named as(±)-nivalones A-B(1a/1b-2a/2b) and(±)-nivalnoids C-D(3a/3b-4a/4b), along with one known enantiomer(±)-anthoponoid G(5a/5b). Human neuroblastoma cells(SH-SY5Y cells) induced by hydrogen peroxide(H_2O_2) were used as oxidative stress models to evaluate the protective activity of the isolated compounds against oxidative damage to nerve cells. It was found that compounds 2a and 3a had a certain protective effect on nerve cells against H_2O_2-induced oxidative damage at concentrations of 50 μmol·L~(-1), which increased the cell survival rate from 44.02%±2.30% to 67.82%±1.12% and 62.20%±1.87%, respectively. Other compounds did not show a significant ability to protect cells from oxidative damage. These findings enrich the chemical constituents of R. nivale and provide valuable information for identifying the structure of its meroterpenoids.

A new benzofuran from Penicillium oxalicum, an endophytic fungus isolated from Pseudostellariaheterophylla / 中草药

Objective: To study the secondary metabolites of Penicillium oxalicum, an endophytic fungus isolated from the medicinal plant Pseudostellariaheterophylla. Methods: The secondary metabolites were isolated by silica gel, Sephadex LH-20 column chromatographies, and prep-TLC methods. Their structures were elucidated by using various spectroscopic techniques including HRESIMS and NMR spectra. Results: A benzofuran compound 5,7-dihydroxy-2-methylbenzofuran-3-carboxylic acid (1), five isocoumarins including (3R,4R)-(-)-4-hydroxymellein (2), O-methylmellein (3), acremonone G (4), decarboxycitrinone (5) and decarboxyhydroxycitrinone (6), four bisabolane-type sesquiterpenoids including (7S,11S)-(+)-12-acetoxysydonic acid (7), (S)-(+)-11-dehydrosydonic acid (8), sydonic acid (9) and 1-hydroxy-boivinianin A (10), as well as two meroterpenoid-type alkaloids decaturin D (11) and decaturinC (12) were isolated. Conclusion: Compound 1 is a new benzofuran compound and named as oxafuranone A, while compounds 2-6 and 10 are characterized from P. oxalicum for the first time.

New Meroterpenoids from a Penicillium sp. Fungus

Two meroterpenoids (1 and 2) along with twelve known compounds (3 – 14) were isolated from the culture broth of a Penicillium sp. fungus collected from Chuja-do, Korea. Based on the results of a combination of spectroscopic analyses, the new compounds, preaustinoids E (1) and F (2), were determined to be epimeric austin-type penta-cyclic lactones.

Intraspecific variation of meroditerpenoids in the brown alga Stypopodium zonale guiding the isolation of new compounds

Abstract Intraspecific variation on meroditerpenoids production by the brown marine alga Stypopodium zonale at four different populations along the Brazilian coast was analyzed using Principal Component Analysis over high-performance liquid chromatography profiles from algae extracts. The ordination of the samples by the similarities of their chromatographic traits showed the existence of three chemotypes: (i) the populations Búzios and Abrolhos which were characterized by the presence of atomaric acid (1), (ii) the population Atol das Rocas which contained the compound stypoldione (2), and (iii) the population Marataízes which was characterized by other peaks that guided the isolation of three new meroditerpenoids stypofuranlactone (3), 10,18-dihydroxy-5′a-desmethyl-5′-acetylatomaric acid (4), and the 10-keto-10-deisopropyliden-5′a-desmethyl-5′-acetylatomaric acid (5) together with the known compound the 10-keto-10-deisopropyliden-atomaric acid (6). The structures and relative stereochemistry of 3, 4 and 5 were elucidated by NMR and MS techniques. The observed chemical differences among populations of S. zonale can be related to its geographic distribution and can open an avenue to the discovery of new compounds in algae.