Two new polyhydroxylated sterols from Ruppia maritima

Penicimides A and B, two novel diels-alder [4 + 2] cycloaddition ergosteroids from Penicillium herquei

Two novel naturally occurring [4 + 2] Diels-Alder cycloaddition ergosteroids (1 and 2), three undescribed oxidized ergosteroids (3-5), and eleven known analogs (6-16) were isolated from Penicillium herquei. Compounds 1 and 2 represent the first reported cycloadducts of a steroid with 1,4,6-trimethyl-1,6-dihydropyridine-2,5-dione or 4,6-dimethyl-1,6-dihydropyridine-2,5-dione to date. Compound 3 is the C-15 epimer of (22E,24R)-9α,11β-dihydroxyergosta-4,6,8(14),22-tetraen-3-one (14). The chemical structures of these compounds were elucidated through widespread spectroscopic analyses, mainly including HRESIMS and 1D and 2D NMR data, calculated 13C NMR-DP4+ analysis, and electronic circular dichroism (ECD) data analyses. Biological evaluations of Compounds 1-16 revealed that 3, 9-11, and 15 inhibited the production of NO in LPS-induced RAW264.7 cells with an IC50 value from 7.37 ± 0.69 to 38.9 ± 2.25 μM (the positive control dexamethasone IC50: 9.54 ± 0.71 μM). In addition, Compound 3 exhibited a potent inhibitory effect on the secretion of the proinflammatory cytokines TNF-α and IL-6, the transcription level of the proinflammatory macrophage markers TNF-α, and the expression of the iNOS protein.

Nine undescribed oxidized ergosterols from the endophytic fungus Penicillium herquei and their cytotoxic activity

A chemical investigation of the EtOAc extract of the endophytic fungus Penicillium herquei led to the isolation of nine undescribed oxidized ergosterols, penicisterols A-I (1-9), along with ten known analogs (10-19). Their structures and absolute configurations were elucidated by a combination of spectroscopic data analysis, quantum-chemical electronic circular dichroism (ECD) calculations and comparisons, [Rh₂(OCOCF₃)₄]-induced ECD experiments, DFT-calculated ¹³C chemical shifts and DP4+ probability analysis. Compound 1 was a rare example of ergosterol in which the bond between C-8 and C-9 is cleaved to form an enol ether. Moreover, compound 2 possessed a rare (2,5-dioxo-4-imidazolidinyl)-carbamic acid ester group substituted at C-3. All undescribed oxidized ergosterols (1-9) were evaluated for their cytotoxic activity against five cancer cell lines including 4T1 (mouse breast carcinoma), A549 (human pulmonary carcinoma), HCT-116 (human colorectal carcinoma), HeLa (human cervical carcinoma) and Hepg2 (human hepatoma carcinoma) cells. Compounds 2 and 3 displayed moderate cytotoxic activity against 4T1, A549 and HeLa cells, with IC₅₀ values ranging from 17.22 to 31.35 μM.

Secondary metabolites of seagrasses (Alismatales and Potamogetonales; Alismatidae): Chemical diversity, bioactivity, and ecological function

Seagrasses are the only higher plants living in fully marine environments; they play a significant role in coastal ecosystems. Seagrasses inhabit the coastal shelves of all continents except Antarctica and can grow in depths of up to 90 m. Because of their eminent ecological importance, innumerous studies have been dedicated to seagrasses and their ecology. However, the phytochemistry has not been equally well investigated yet and many of the existing studies in chemical ecology are only investigating the chemistry at the level of compound classes, e.g. phenolics, and not at the level of chemically defined metabolites. In the present review, the existing literature on secondary metabolites of seagrasses, their known source seagrasses, their bioactivity, and ecological function are compiled and critically assessed. Moreover, research gaps are highlighted and avenues for future research are discussed. Currently, a total of 154 chemically defined natural products have been reported from the about 70 seagrass species known worldwide. Compounds reported include simple phenols derivatives (four compounds), phenylmethane derivatives (14 compounds), phenylethane derivatives (four compounds), phenylpropane derivatives including their esters and dimers (20 compounds), chalkones (four compounds), flavonoids including catechins (57 compounds), phenylheptanoids (four compounds), one monoterpene derivative, one sesquiterpene, diterpenoids (13 compounds), steroids (31 compounds), and one alkaloid. Most of the existing bioactivity studies of seagrass metabolites and extracts have been directed to potential cytotoxic, antimicrobial, or antimacrofouling activity. Antimicrobial studies have been performed towards panels of both human pathogens and ecologically relevant pathogens. In the antimacrofouling studies, investigations of the potential of zosteric acid from the genus Zostera are the most numerous and have yielded so far the most interesting results. Studies on the chemical ecology of seagrasses often have been focused on variation in phenolic compounds and include but are not limited to studies on variation due to abiotic factors, seasonal variation, variation in response to grazing by fish or sea urchins, or following microbial attack.

Steroids with anti-inflammatory activity from Vernonia nigritiana Oliv. & Hiern

The leaves of Vernonia nigritiana Oliv. & Hiern. (Asteraceae) were investigated for their in vivo topical anti-inflammatory properties, following a bioassay-oriented fractionation approach. Petroleum ether, chloroform and chloroform-methanol extracts inhibited the Croton oil-induced ear dermatitis in mice. The chloroform extract was only about half as active as the non steroidal anti-inflammatory drug indomethacin (ID50=237 and 93 μg/cm(2), respectively). Phytochemical investigation of this extract led to the isolation of nine polyhydroxylated stigmasterol glycosides and six polyhydroxylated stigmasterols. Their structures were elucidated by NMR, MS and chemical methods. Each compound exerted a significant anti-oedema activity, the most active being 1 (3β-O-β-D-glucopyranosyloxy-5α-stigmasta-7,9(11),24(28)Z-triene-6β,16β,26,29-tetrol) and 3 (3β-O-β-D-glucopyranosyloxy-5α-stigmasta-7,9(11),24(28)Z-triene-6β,16β,29-triol), only two and five fold less potent than the steroidal drug hydrocortisone (ID50=0.10, 0.21 and 0.04 μmol/cm(2), respectively). Compound 1 (50 μM) also completely inhibited the transcription factor NF-κB in vitro.

Chemical Constituents of the Aquatic Plant Schoenoplectus lacustris: Evaluation of Phytotoxic Effects on the Green Alga Selenastrum capricornutum

Forty-nine secondary metabolites were isolated from aqueous and alcoholic extracts of the aquatic plant Shoenoplectus lacustris. All compounds were characterized based on spectroscopic data. Eleven free and glycosylated low-molecular polyphenols, 17 cinnamic acid and dihydrocinnamic acid derivatives, 11 flavonoids, and 10 C13 nor-isoprenoids were identified. The structure of the new compound, 1-benzoyl-glycerol-2-alpha-L-arabinopyranoside, was elucidated by 2D NMR experiments (COSY, HSQC, HMBC, NOESY). To evaluate potential phytotoxic effects, all compounds were tested on the green alga Selenastrum capricornutum, a unicellular organism commonly used in tests of toxicity as a bioindicator of eutrophic sites. The most active compound was (-)-catechin, showing an inhibition similar to that of the algaecide CuSO4.