Euphane triterpenoids of Cassipourea lanceolata from the Madagascar rainforest

The role of nanomaterials in enhancing natural product translational potential and modulating endoplasmic reticulum stress in the treatment of ovarian cancer

Ovarian cancer, and particularly its most frequent type, epithelial ovarian carcinoma, constitutes one of the most dangerous malignant tumors among females. Substantial evidence has described the potential of phytochemicals against ovarian cancer. The effect of natural compounds on endoplasmic reticulum (ER) stress is of great relevance in this regard. In ovarian cancer, the accumulation of misfolded proteins in the ER lumen results in decompensated ER stress. This leads to deregulation in the physiological processes for the posttranslational modification of proteins, jeopardizes cellular homeostasis, and increases apoptotic signaling. Several metabolites and metabolite extracts of phytochemical origin have been studied in the context of ER stress in ovarian cancer. Resveratrol, quercetin, curcumin, fucosterol, cleistopholine, fucoidan, and epicatechin gallate, among others, have shown inhibitory potential against ER stress. The chemical structure of each compound plays an important role concerning its pharmacodynamics, pharmacokinetics, and overall effectiveness. Studying and cross-comparing the chemical features that render different phytochemicals effective in eliciting particular anti-ER stress actions can help improve drug design or develop multipotent combination regimens. Many studies have also investigated the properties of formulations such as nanoparticles, niosomes, liposomes, and intravenous hydrogel based on curcumin and quercetin along with some other phytomolecules in ovarian cancer. Overall, the potential of phytochemicals in targeting genetic mechanisms of ovarian cancer warrants further translational and clinical investigation.

Progress toward the De Novo Asymmetric Synthesis of Euphanes

Progress toward an asymmetric synthesis of euphanes is described. A C14-desmethyl euphane system possessing five differentially substituted and electronically distinct alkenes has been prepared. The route employed is based on sequential metallacycle-mediated annulative cross-coupling, double asymmetric Brønsted acid mediated intramolecular Friedel-Crafts alkylation, and an oxidative rearrangement to establish the requisite C10 quaternary center. These studies have also led to the discovery of a novel euphane-based modulator of the Liver X Receptor.

Natural Compounds in Sex Hormone-Dependent Cancers: The Role of Triterpenes as Therapeutic Agents

Sex hormone-dependent cancers currently contribute to the high number of cancer-related deaths worldwide. The study and elucidation of the molecular mechanisms underlying the progression of these tumors was a double-edged sword, leading to the expansion and development of new treatment options, with the cost of triggering more aggressive, therapy resistant relapses. The interaction of androgen, estrogen and progesterone hormones with specific receptors (AR, ER, PR) has emerged as a key player in the development and progression of breast, ovarian, prostate and endometrium cancers. Sex hormone-dependent cancers share a common and rather unique carcinogenesis mechanism involving the active role of endogenous and exogenous sex hormones to maintain high mitotic rates and increased cell proliferation thus increasing the probability of aberrant gene occurrence and accumulation highly correlated with abnormal cell division and the occurrence of malignant phenotypes. Cancer related hormone therapy has evolved, currently being associated with the blockade of other signaling pathways often associated with carcinogenesis and tumor progression in cancers, with promising results. However, despite the established developments, there are still several shortcomings to be addressed. Triterpenes are natural occurring secondary metabolites biosynthesized by various pathways starting from squalene cyclization. Due to their versatile therapeutic potential, including the extensively researched antiproliferative effect, these compounds are most definitely a cornerstone in the research and development of new natural/semisynthetic anticancer therapies. The present work thoroughly describes the ongoing research related to the antitumor activity of triterpenes in sex hormone-dependent cancers. Also, the current review highlights both the biological activity of various triterpenoid compounds and their featured mechanisms of action correlated with important chemical structural features.

The effect of isolates from Cassipourea flanaganii (Schinz) alston, a plant used as a skin lightning agent, on melanin production and tyrosinase inhibition

ETHNOPHARMACOLOGICAL RELEVANCE

The Zulu and Xhosa people of South Africa use the stem bark of Cassipourea flanaganii as a skin-lightning cosmetic.

AIM OF THE STUDY

To isolate and identify compounds responsible for the skin lightning properties from the stem bark of Cassipourea flanaganii and to evaluate their cytotoxicity towards skin cells.

MATERIALS AND METHODS

Extracts from the stem bark of Cassipourea flanaganii were isolated using chromatographic methods and structures were determined using NMR, IR and MS analysis. The tyrosinase inhibitory activity and the ability to inhibit the production of melanin were determined using human primary epidermal melanocyte cells. Cytoxicity was established using the same melanocytes and a neutral red assay.

RESULTS

One previously undescribed compound, ent-atis-16-en-19-al (1) along with the known ent-atis-16-en-19-oic acid (2), ent-atis-16-en-19-ol (3), ent-kaur-16-en-19-oic acid (4), ent-kaur-16-en-19-al (5), ent-manoyl oxide (6), guinesine A (7), guinesine B (8), guinesine C (9), lichenxanthone (10), 2,4-dihydroxy-3,6-dimethyl benzoic acid methyl ester (11), lynoside (12), lupeol (13), β-amyrin (14), docosyl ferulate (15), stigmasterol, sitosterol and sitosterol-O-glucoside were isolated in this investigation. An impure fraction containing compound 3 was acetylated to obtain 19-acetoxy-ent-atis-16-ene (3a). Compounds 10 and 11 are usually isolated from lichen, hence they are possible contaminants of lichen harvested with the bark. Compounds 1, 3a, 5-14 were not significantly cytotoxic to the primary epidermal melanocyte cells (P > 0.05) when compared to the negative and positive controls (DMSO, 0.1% and hydrogen peroxide, 30 wt% in water). Inhibition of tyrosinase was significantly greater with respect to the negative control (P < 0.001) for compounds 3a, 5-8 and 9-10 at 10 μM and for compounds 5-8 and 9-10 at 100 μM. Compared to hydroquinone (the positive control) at 10 μM, the level of inhibition was comparable or to that of compounds 3a, 5, 6, and 8-10 at 10 μM, with 9 and 10 showing a greater level of inhibition. Inhibition of melanin was both concentration and time dependent for all compounds tested with higher melanin content at 24 h compared to 48 h s and at 10 mM compared to100 mM at both time points; melanin content was significantly lower for hydroquinone at both time points and concentrations.

CONCLUSIONS

Compounds 1, 5-14, isolated from Cassipourea flanaganii and the derivative 3a showed low cytotoxicity. All compounds had a clear time and concentration dependent effect on melanin content which did not appear to be dependent on their inhibition of tyrosinase.

3-Hydroxy-8,14-secogammacera-7,14-dien-21-one: A New Onoceranoid Triterpenes from Lansium domesticum Corr. cv kokossan

A new onoceranoid triterpenes, namely 3-hydroxy-8,14-secogammacera-7,14-dien-21-one (1), has been isolated from the fruit peels of Lansium domesticum Corr. cv kokossan. The structure of 1 was determined on the basis of spectroscopic data including infrared, 1D and 2D-NMR, as well as high resolution mass spectroscopy analysis. Compound 1 showed a weak activity against MCF-7 breast cancer cell lines.

Endertiins A-B, two lanostane triterpenoids from the fruit bodies of the mushoom Humphreya endertii

Two new lanostane triterpnenoids named endertiins A and B (1 and 2) together with two known compounds as ganodecalone A (3) and ergosterol (4) have been successfully isolated from the cultivated fruit bodies of the mushroom Humphreya endertii Stey (Ganodermataceae). Their structures were elucidated by a combination of HR-MS and 2 D NMR spectroscopic analyses. In addition, endertiins A and B (1 and 2) were evaluated their cytotoxicity against two cancer cell lines, MCF7 (human breast carcinoma) and LU (human lung carcinoma). The result showed that endertiin A (1) could inhibit the growth of MCF-7 cells with its IC₅₀ value of 71.16 ± 6.25 µg/ml.

Renoprotective Mono- and Triterpenoids from the Fruit of Gardenia jasminoides

This paper describes the isolation and characterization of 17 new and 12 known terpenoids from the fruit of Gardenia jasminoides. The structures of eight new triterpenoids and nine new monoterpenoids, including their absolute configurations, were defined by spectroscopic analysis in combination of quantum chemical electronic circular dichroism (ECD), vibrational circular dichroism (VCD), and gauge-independent atomic orbital (GIAO) NMR calculations. The cytoprotective effects of the isolated compounds against lipopolysaccharide (LPS)-induced apoptosis in normal rat kidney tubule epithelioid (NRK 52e) cells were investigated in vitro. Compounds 10, 18, 20, 21, 24, and 26 exhibited significant protective effects with EC₅₀ values from 14.2 nM to 1.6 μM.

Structure of constituents isolated from the bark of Cassipourea malosana and their cytotoxicity against a human ovarian cell line

Three aromatic compounds, 2α,3α-epoxyflavan-5,7,4'-triol-(4β → 8)-afzelechin (1), 2β,3β-epoxyflavan-5,7,4'-triol-(4α → 8)-epiafzelechin (2), and methyl 4-ethoxy-2-hydroxy-6-propylbenzoate (3), as well as eight known compounds (4-11) were isolated from the bark of Cassipourea malosana (Rhizophoraceae). Their structures were determined on the basis of an analysis of spectroscopic data. The in vitro cytotoxic activities of these compounds against human ovarian cancer cell line TOV21G were evaluated. Most compounds showed little activity; however, the methyl derivatives of flavan dimers (1a and 2a) showed higher activity (IC₅₀ value of 30.3 and 75.4 μM) than parent compounds 1 and 2.

Novel Bioactive Natural Products Isolated from Madagascar Plants and Marine Organisms (2009-2017)

Madagascar's rain forests and tropical dry forests are home to numerous endemic plant species and the island is considered a biodiversity hotspot. About 80% of the Madagascan (Malagasy) population relies on traditional medicines that have been proven to contain a variety of biologically active compounds. In the search for bioactive compounds from Madagascan biodiversity, we accessed and collected most of the literature dealing with the isolation, structure elucidation, and biological activities of organic small molecules originating from Madagascan plants and marine organisms. Since we published the first review of this work in 2009 (Curr. Med. Chem., 17, 2010, Hou and Harinantenaina), the present paper covers the isolation, structures, and bioactivity of 182 new secondary metabolites isolated from Malagasy higher plants and marine organisms in the last seven years (2009-2017).

Lanostane-type triterpenoids from the fruiting body of Ganoderma calidophilum

To search for active anti-cancer constituents in the fruiting body of Ganoderma calidophilum, we have successfully isolated four previously undescribed spiro-lactone lanostane triterpenoids (spiroganocalitones A-D), two previously undescribed lanostanoids (ganodecalones A and B) together with twenty-three known ones. The structures of the six previously undescribed compounds were elucidated based on 1D, 2D-NMR, and HRMS analyses. Ganoderone A showed moderate cytotoxic activity against K562, BEL7402, and SGC790 cell lines with IC₅₀ values of 7.62, 6.28, and 3.55 μM, respectively.

New Enzyme-Inhibitory Triterpenoid from Marine Macro Brown Alga Padina boergesenii Allender & Kraft

In continuation to our study of the chemical and biological potential of the secondary metabolites isolated from Omani seaweeds, we investigated a marine brown alga, Padina boergesenii. The phytochemical investigation resulted in the isolation of a new secondary metabolite, padinolic acid (1), along with some other semi-pure fractions and sub-fractions. The planar structure was confirmed through MS and NMR (1D and 2D) spectral data. The NOESY experiments coupled with the biogenetic consideration were helpful in assigning the stereochemistry in the molecule. Compound 1 was subjected to enzyme inhibition studies using urease, lipid peroxidase, and alpha-glucosidase enzymes. Compound 1 showed low to moderate α-glucosidase and urease enzyme inhibition, respectively, and moderate anti-lipid peroxidation activities. The current study indicates the potential of this seaweed and provides the basis for further investigation.

The chemistry and bioactivity of Southern African flora I: a bioactivity versus ethnobotanical survey of alkaloid and terpenoid classes

As a whole, the African continent is highly endowed with a huge floral biodiversity.

Lithocarpic Acids A-N, 3,4-seco-Cycloartane Derivatives from the Cupules of Lithocarpus polystachyus

Fourteen new 3,4-seco-cycloartane-type triterpenes, lithocarpic acids A-N (1-14), together with one known compound, coccinetane E (15), were identified from the cupules of Lithocarpus polystachyus. The structures of 1-14 were determined by spectroscopic data analysis and chemical methods, and the absolute configurations of 1 and 4 were defined unequivocally by X-ray crystallography using Cu Kα radiation. Compounds 1-15 are the first examples of 3,4-seco-cycloartane derivatives isolated from the genus Lithocarpus. Among them, compounds 1 and 2, 9 and 10, and 11 and 12 were found to be three pairs of C-24 epimers, while compounds 7 and 8 represent the first examples of 3,4-seco-norcycloartane-type triterpenes. Compound 1, as the major component of the plant extract, showed potent antibacterial activity against Micrococcus luteus and Bacillus subtilis, with MIC values of 3.1 and 6.3 μg/mL, respectively, as well as inhibitory activity against human and mouse 11β-hydroxysteroid dehydrogenase type 1, with IC50 values of 1.9 and 0.24 μM, respectively.

Triterpenoids

This review covers the isolation and structure determination of triterpenoids, including squalene derivatives, protostanes, lanostanes, holostanes, cycloartanes, dammaranes, euphanes, tirucallanes, tetranortriterpenoids, quassinoids, lupanes, oleananes, friedelanes, ursanes, hopanes, serratanes and saponins; 305 references are cited.