Two new cadinene-type sesquiterpene glycosides from Dendrobium findlayanum

Two new and one known cadinene-type sesquiterpene glycosides, findlayanosides A-B (1-2) and dendronobiloside D (3), were isolated from the stems of Dendrobium findlayanum. This is the first report that cadinene-type sesquiterpene glycosides were isolated from D. findlayanum. The structures of compounds 1 and 2 were elucidated by extensive spectroscopic analyses, and their absolute configurations were confirmed by electronic circular dichroism (ECD) calculations. The obtained compounds were evaluated for their cytotoxicity against HL-60, SMMC-7721, A-549 and MCF-7 human cancer cells, and no obvious cytotoxic activity was observed at the concentration of 25 μΜ.

Current Knowledge Regarding Pharmacological Profile and Chemical Constituents of Gynura procumbens

Gynura procumbens (Lour.) Merr. is a well-known plant used in the folkloric medicine in tropical Asian countries. The plant is prevalently employed by traditional healers in the treatment of diabetes, cancer, hypertension, inflammation, fever and skin disorders. Several scientific studies reported that, Gynura procumbens possesses considerable therapeutic value for the development of emerging treatment options. The diverse pharmacological effects of this plant are attributed to its vast phytoconstituent content. Different chemical classes including alkaloids, flavonoids, phenolics, steroids, proteins and polysaccharides have been isolated from this plant. In this review, we tried to explore the different aspects of Gynura procumbens as an established medicinal plant. The data gathered here give an indication that the plant Gynura procumbens is a good natural source of chemical compounds with different types of pharmacological actions and these chemical compounds can be used as model for the development of de novo therapeutic agents.

Traditional uses, phytochemistry, pharmacology and toxicology of the genus Gynura (Compositae): A comprehensive review

ETHNOPHARMACOLOGICAL RELEVANCE

Gynura cass., belonging to the tribe Senecoineae of the family Compositae, contains more than 40 accepted species as annual or perennial herbs, mainly distributed in Asia, Africa and Australia. Among them, 11 species are distributed in China. Many of the Gynura species have been used as traditional herbal medicines for the treatment of diabetes mellitus, rheumatism, eruptive fever, gastric ulcer, bleeding, abscesses, bruises, burning pains, rashes and herpes zoster infection in tropical Asia countries such as China, Thailand, Indonesia, Malaysia, and Vietnam. Some of the species have been used as vegetables, tea beverage or ornamental plants by the local people.

AIM OF THE STUDY

A more comprehensive and in-depth review about the geographical distribution, traditional uses, chemical constituents and pharmacological activities as well as safe and toxicity of Gynura species has been summarized, hoping to provide a scientific basis for rational development and utilization as well as to foster further research of these important medicinal plant resources in the future.

MATERIALS AND METHODS

A review of the literature was performed based on the existing peer-reviewed researches by consulting scientific databases including Web of Science, PubMed, Elsevier, Google Scholar, SciFinder and China National Knowledge Infrastructure.

RESULTS

Many of the Gynura species have been phytochemically studied, which led to the isolation of more than 338 compounds including phenolics, flavonoids, alkaloids, terpenoids, steroids, cerebrosides, aliphatics and other compounds. Pharmacological studies in vitro and in vivo have also confirmed the various bioactive potentials of extracts or pure compounds from many Gynura plants, based on their claimed ethnomedicinal and anecdotal uses, including antioxidant, anti-inflammation, anticancer, antidiabetic, antihypertension, antibacterial and other activities. However, pyrrolizidine alkaloids (PAs) pose a threat to the medication safety and edible security of Gynura plants because of toxicity issues, requiring the need to pay great attention to this phenomenon.

CONCLUSION

The traditional uses, phytochemistry and pharmacology of Gynura species described in this review demonstrated that these plants contain a great number of active constituents and display a diversity of pharmacological activities. However, the mechanism of action, structure-activity relationship, potential synergistic effects and pharmacokinetics of these components need to be further elucidated. Moreover, further detailed research is urgently needed to explain the mechanisms of toxicity induced by PAs. In this respect, effective detoxification strategies need to be worked out, so as to support the safe and reasonable utilization of Gynura plant resources in the future.

Ethnomedicinal uses, phytochemistry, and biological activities of plants of the genus Gynura

ETHNOPHARMACOLOGICAL RELEVANCE

The genus Gynura (Compositae) includes around 46 species and is native to the tropical regions of Southeast Asia, Africa and Australia. Many species within this genus are used in ethnomedicine to treat various disorders including skin diseases, injuries, ulcers, wounds, burns, sores, scalds, as well as for the management of diabetes, hypertension, hyperlipidemia, constipation, rheumatism, bronchitis and inflammation.

AIM OF THE REVIEW

This review is an attempt to provide scientific information regarding the ethnopharmacology, phytochemistry, pharmacological and toxicological profiles of Gynura species along with the nomenclature, distribution, taxonomy and botanical features of the genus. A critical analysis has been undertaken to understand the current and future pharmaceutical prospects of the genus.

MATERIALS & METHODS

Several electronic databases, including Google scholar, PubMed, Web of Science, Scopus, ScienceDirect, SpringerLink, Semantic Scholar, MEDLINE and CNKI Scholar, were explored as information sources. The Plant List Index was used for taxonomical authentications. SciFinder and PubChem assisted in the verification of chemical structures.

RESULTS

A large number of phytochemical analyses on Gynura have revealed the presence of around 342 phytoconstituents including pyrrolizidine alkaloids, phenolic compounds, chromanones, phenylpropanoid glycosides, flavonoids, flavonoid glycosides, steroids, steroidal glycosides, cerebrosides, carotenoids, triterpenes, mono- and sesquiterpenes, norisoprenoids, oligosaccharides, polysaccharides and proteins. Several in vitro and in vivo studies have demonstrated the pharmacological potential of Gynura species, including antidiabetic, anti-oxidant, anti-inflammatory, antimicrobial, antihypertensive and anticancer activities. Although the presence of pyrrolizidine alkaloids within a few species has been associated with possible hepatotoxicity, most of the common species have a good safety profile.

CONCLUSIONS

The importance of the genus Gynura both as a prominent contributor in ethnomedicinal systems as well as a source of promising bioactive molecules is evident. Only about one fourth of Gynura species have been studied so far. This review aims to provide some scientific basis for future endeavors, including in-depth biological and chemical investigations into already studied species as well as other lesser known species of Gynura.

Inhibition of biofilm formation, quorum sensing and other virulence factors in Pseudomonas aeruginosa by polyphenols of Gynura procumbens leaves

Quorum sensing (QS) enables virulence factors in bacteria for biofilm formation and pathogenic invasion. Therefore, quorum quenching (QQ), disruption of QS circuit, becomes an alternative antimicrobial therapy. In this study, leaf extract of Gynura procumbens (GP) was used to inhibit biofilm and virulent factors in Pseudomonas aeruginosa. The extract inhibited the biofilm production (p ≤ 0.05) in P. aeruginosa strains MZ2F and MZ4A. The minimum biofilm eradication concentration (MBEC) was recorded at 250 and 500 μg/ml while total activity was found at 288 and 144 ml/g, respectively. Moreover, a significant reduction of virulence factors (p ≤ 0.05) at sub-MBEC without affecting the growth implies the QQ action of the extract. The bioactive fractions were rich in polyphenols and tentatively identified as quercetin and myricetin (R_f=0.53-0.60). Furthermore, we employed computational methods to validate our findings and their interactions with QS receptors (LasR and RhlR). Interestingly, docking studies have also shown that quercetin and myricetin are the promising anti-QS agents out of 31 GP compounds. Notably, their binding affinity ranged between -9.77 and -10.52 kcal/mol for both QS receptors, with controls ranging from -5.40 to -8.97 kcal/mol. Besides, ΔG of quercetin and myricetin with LasR was -71.56 and -74.88 kcal/mol, respectively. Moreover, compounds were suitable drug candidates with stable binding interactions. Therefore, the anti-QS activity of GP leaves and the identified polyphenols can be used in developing QQ-based therapeutics. Communicated by Ramaswamy H. Sarma.

Terpenoids from the Fermented Broths of Coprinellus radians

One new sesquiterpenoid, namely coprinol (1), along with guanacastanes J (2), E (3) and N (4), were isolated from the ethyl acetate extracts of the fermented broths of the fungal strain Coprinellus radians#1168. Their structures were elucidated on the basis of spectroscopic data analysis. The growth inhibitory activities against A549 of 1-4 were evaluated, and only 4 exhibited moderate growth inhibitory activity with a GI50 value of 18.2 μM compared with fluorouracil (GI50 = 3.6 μM). All the compounds were also subjected to antifungal assay against Candida albicans ATCC 18804, C. albicans SC-5314, Cryptococcus neoformans ATCC 13690 and Saccharomyces cerevisiae ATCC 2345; all showed mild antifungal activity with MIC values of 128.0 μg/mL for 1-3 and 64.0 μg/mL for 4 in comparison with amphotericin B (MIC = 0.25 μg/mL) and ketoconazole (MIC = 1.0 μg/mL).

Structurally diverse stilbene dimers from Gnetum montanum Markgr.: studies on the 1H chemical shift differences between dimeric stilbene epimers correlating to the relative configurations

Nine new dimeric stilbenoids were isolated from Gnetum montanum. The key ¹H NMR shifts correlating to the configuration of C-7 of indane-type dimeric stilbenes were summarized. The misassigned structures of gnetuhainins D and E were revised.