Prenylated flavanone derivatives isolated from Erythrina addisoniae are potent inducers of apoptotic cell death

Adsorption and desorption of flavonoids on activated carbon impregnated with different metal ions

In this study, four metal ions Mg²⁺, Al³⁺, Fe³⁺, and Zn²⁺ were loaded on the surface of activated carbon by an impregnation method coupled with high-temperature calcination to prepare modified activated carbon. Scanning electron microscopy, specific surface area and pore size analysis, X-ray diffraction, and Fourier infrared spectroscopy were used to evaluate the structure and morphology of the modified activated carbon. The findings show that the modified activated carbon had a large microporous structure and high specific surface area, both of which significantly improved absorbability. This study also investigated the adsorption and desorption kinetics of the prepared activated carbon for three flavonoids with representative structures. The adsorption amounts of quercetin, luteolin, and naringenin in the blank activated carbon reached 920.24 mg g^-1, 837.07 mg g^-1, and 677.37 mg g^-1, while for activated carbon impregnated with Mg, the adsorption amounts reached 976.34 mg g^-1, 963.39 mg g^-1, and 817.98 mg g^-1, respectively; however, the desorption efficiencies of the three flavonoids varied a lot. The differences in desorption rates of naringenin as compared with quercetin and luteolin in the blank activated carbon were 40.13% and 46.22%, respectively, and the difference in desorption rates increased to 78.46% and 86.93% in the activated carbon impregnated with Al. The differences provide a basis for the application of this type of activated carbon in the selective enrichment and separation of flavonoids.

Phytochemistry and pharmacology of natural prenylated flavonoids

Prenylated flavonoids are a special kind of flavonoid derivative possessing one or more prenyl groups in the parent nucleus of the flavonoid. The presence of the prenyl side chain enriched the structural diversity of flavonoids and increased their bioactivity and bioavailability. Prenylated flavonoids show a wide range of biological activities, such as anti-cancer, anti-inflammatory, neuroprotective, anti-diabetic, anti-obesity, cardioprotective effects, and anti-osteoclastogenic activities. In recent years, many compounds with significant activity have been discovered with the continuous excavation of the medicinal value of prenylated flavonoids, and have attracted the extensive attention of pharmacologists. This review summarizes recent progress on research into natural active prenylated flavonoids to promote new discoveries of their medicinal value.

An overview of techniques and strategies for isolation of flavonoids from the genus Erythrina

Plants in the genus Erythrina is a potential source of chemical constituents, one of which is flavonoids, which have diverse bioactivities. To date, literature on the flavonoids from the genus Erythrina has only highlighted the phytochemical aspects, so this review article will discuss isolation techniques and strategies for the first time. More than 420 flavonoids have been reported in the Erythrina genus, which are grouped into 17 categories. These flavonoid compounds were obtained through isolation techniques and strategies using polar, semi-polar, and non-polar solvents. Various chromatographic techniques have been developed to isolate flavonoids using column flash chromatography, quick column chromatography, centrifugally accelerated thin-layer chromatography, radial chromatography, medium-pressure column chromatography, semi-preparative high-performance liquid chromatography, and preparative high-performance liquid chromatography. Chromatographic processes for isolating flavonoids can be optimized using multivariate statistical applications such as response surface methodology with central composite design, Box-Behnken design, Doehlert design, and mixture design.

Epimesatines A-I, nine undescribed prenylated flavonoids with SPHK1 inhibitory activities from Epimedium sagittatum maxim

Epimesatines A-I, nine undescribed prenylated flavonoids, along with ten known analogues, were isolated from the aerial parts of Epimedium sagittatum Maxim. The structures and absolute configurations of epimesatines A-I were determined using a combination of spectroscopic data, Rh₂(OCOCF₃)₄-induced electronic circular dichroism (ECD) experiments, ECD comparisons, and X-ray crystallography analysis. Epimesatines A and I displayed notable activities on the viabilities of human non-small cell lung cancer (NSCLC) A549 cells with IC₅₀ values of 1.77 and 9.97 μM, respectively. Furthermore, epimesatines A and I significantly inhibited the expression of sphingosine kinase 1 (SPHK1) in A549 cells. In addition, none of these compounds showed obvious toxicity on normal human lung bronchial epithelial BEAS-2B cells.

Cytotoxic Flavonoids from the Leaves and Twigs of Murraya Tetramera

Cytotoxic flavonoids of Murraya tetramera were investigated in this study. A novel flavonoid and twelve known flavonoids, including seven flavones (1-7), three flavanones (8-10), and three chalcones (11-13) were isolated from the leaves and twigs of Murraya tetramera. Chemical structures were elucidated by NMR combined with MS spectral analysis, and the new compound (6) was confirmed as 3',5'-dihydroxy-5,6,7,4'-tetramethoxyflavone. Furthermore, all the isolated flavonoids were evaluated for their cytotoxicities against murine melanoma cells (B16), and human breast cancer cells (MDA-MB-231) by CCK-8 assay. Among them, compounds 7, 13, and 5 exhibited potent cytotoxic activities against B16 cell lines (IC50 = 3.87, 7.00 and 8.66 μg/mL, respectively). Compounds 5, 13, and 12 displayed potent cytotoxicities against MDA-MB-231 cell lines (IC50 = 3.80, 5.95 and 7.89 μg/mL, respectively). According to the correlation of the structure and activity analysis, 5-hydroxyl and 8-methoxyl substituents of the flavone, 8-methoxyl substituent of the flavanone, and 3',5'-methoxyl substituents of the chalcone could be critical factors of the high cytotoxicity. The results indicated that the active flavonoids have potential to be developed as leading compounds for treating cancers.

New Acetophenones and Chromenes from the Leaves of Melicope barbigera A. Gray

The dichloromethane extract from leaves of Melicope barbigera (Rutaceae), endemic to the Hawaiian island of Kaua'i, yielded four new and three previously known acetophenones and 2H-chromenes, all found for the first time in M. barbigera. The structures of the new compounds obtained from the dichloromethane extract after purification by chromatographic methods were unambiguously elucidated by spectroscopic analyses including 1D/2D NMR spectroscopy and HRESIMS. The absolute configuration was determined by modified Mosher's method. Compounds 2, 4 and the mixture of 6 and 7 exhibited moderate cytotoxic activities against the human ovarian cancer cell line A2780 with IC₅₀ values of 30.0 and 75.7 µM for 2 and 4, respectively, in a nuclear shrinkage cytotoxicity assay.

Promising Antioxidant Activity of Erythrina Genus: An Alternative Treatment for Inflammatory Pain?

The negative impact that oxidative stress has on health is currently known. The complex mechanism of free radicals initiates a series of chain reactions that contribute to the evolution or development of different degenerative disorders. Likewise, these disorders are usually accompanied by inflammatory processes and, therefore, pain. In this sense, reactive oxygen species (ROS) have been shown to promote the nociceptive process, but effective treatment of pain and inflammation still represents a challenge. Over time, it has been learned that there is no single way to relieve pain, and as long as there are no other alternatives, the trend will continue to apply multidisciplinary management, such as promote the traditional use of the Erythrina genus to manage pain and inflammation. In this sense, the Erythrina genus produces a wide range of secondary metabolites, including flavanones, isoflavones, isoflavones, and pterocarpans; these compounds are characterized by their antioxidant activity. Phenolic compounds have demonstrated their ability to suppress pro-oxidants and inhibit inflammatory signaling pathways such as MAPK, AP1, and NFκB. Although there is preclinical evidence supporting its use, the pharmacological effect mechanisms are not entirely clear. Nowadays, there is a fast advancement in knowledge of the disciplines related to drug discovery, but most of nature's medicinal potential has not yet been harnessed. This review analyzes the decisive role that the Erythrina genus could play in managing inflammatory pain mediated by its compounds and its uses as an antioxidant.

Bio- and chemo- transformations of glabranin and 7-O-methylglabranin and cytotoxic evaluations of the transformed products

The biotransformation of glabranin (1) with Aspergillus niger and Cunninghamella blakesleeana favoured the formation of benzofuran derivatives (3 and 4), while in contrast, its acid-catalysed chemical transformation favoured the formation of benzopyran derivatives (6 and 7). Compound 6 was further biooxidised at C-4'. Biotransformation of 7-O-methylglabranin (2) proceeded via oxidation of the prenyl group and C-4' by the same fungi, and the obtention of 11 mimics the biosynthesis of this last compound. Some compounds displayed moderate antiproliferative activity against selected human cancer cell lines, with glabranin being the most active, suggesting that the prenyl group and the phenol at C-7 are important structural determinants for cytotoxicity.

Flavonoids and other Non-alkaloidal Constituents of Genus Erythrina: Phytochemical Review

BACKGROUND

Genus Erythrina belongs to family Fabaceae, which is widely distributed in tropical and subtropical areas. It has been used in both traditional herbal medicines and pharmacological applications. Original research articles and publications on the overview of alkaloids related to this genus are available, but a supportive systematic review account which highlighted phytochemical aspects of other types of secondary metabolites is currently insufficient.

OBJECTIVE

With the utilization of data and information from SCI-Finder, Google Scholar, the Web of Science, Scopus, Science Direct, PubMed, Chemical Abstracts, ACS journals, Springer, Taylor Francis, Bentham Science and IOP Science, the reliable material sources of this systematic review paper were obtained from the literature published from the 1980s to now.

CONCLUSION

A vast amount of data showed that the non-alkaloidal secondary metabolites were obtained from genus Erythrina with various classes of chemical structures. Herein, approximately five hundred constituents were isolated, comprising flavonoids, terpenoids, saponins, phytosterols, phenols, arylbenzofurans, coumarins, alcohols, ceramides, mono-sugars and fatty acid derivatives. In agreement with the previous phytochemical reports on the plants of the family Fabaceae, flavonoids reached a high amount in the plants of genus Erythrina. Numerous biological activity investigations such as anti-bacteria, anti-cancer, anti-virus using isolated compounds from Erythrina species suggested that secondary metabolites of Erythrina plants are now becoming the promising agents for drug developments.

Protein Tyrosine Phosphatase 1B Inhibitors: A Novel Therapeutic Strategy for the Management of type 2 Diabetes Mellitus

Diabetes is one of the most common endocrine non-communicable metabolic disorders which is mainly caused either due to insufficient insulin or inefficient insulin or both together and is characterized by hyperglycemia. Diabetes emerged as a serious health issue in the industrialized and developing country especially in the Asian pacific region. Out of the two major categories of diabetes mellitus, type 2 diabetes is more prevalent, almost 90 to 95% cases, and the main cause of this is insulin resistance. The main cause of the progression of type 2 diabetes mellitus has been found to be insulin resistance. The type 2 diabetes mellitus may be managed by the change in lifestyle, physical activities, dietary modifications and medications. The major currently available management strategies are sulfonylureas, biguanides, thiazolidinediones, α-glucosidase inhibitors, dipeptidyl peptidase-IV inhibitors, and glucagon-like peptide-1 (GLP-1) agonist. Binding of insulin on the extracellular unit of insulin receptor sparks tyrosine kinase of the insulin receptor which induces autophosphorylation. The phosphorylation of the tyrosine is regulated by insulin and leptin molecules. Protein tyrosine phosphatase-1B (PTP1B) works as a negative governor for the insulin signalling pathways, as it dephosphorylates the tyrosine of the insulin receptor and suppresses the insulin signalling cascade. The compounds or molecules which inhibit the negative regulation of PTP1B can have an inductive effect on the insulin pathway and finally help in the management of diabetes mellitus. PTP1B could be an emerging therapeutic strategy for diabetes management. There are a number of clinical and basic research results which suggest that induced expression of PTP1B reduces insulin resistance. In this review, we briefly elaborate and explain the place of PTP1B and its significance in diabetes as well as a recent development in the PTP1B inhibitors as an antidiabetic therapy.

Potent Cytotoxic Natural Flavonoids: The Limits of Perspective

BACKGROUND

Besides the numerous biologic and pharmacologic functions in the human body that act as potent antioxidants, flavonoids (flavones, flavanones, flavonols, flavanols and isoflavones) are noted as cancer preventive or therapeutic agents.

METHODS

This review summarizes the published data using PubMed, Science Direct, and Scopus.

RESULTS

In this context, recognition and introduction of the most active cytotoxic flavonoids as promising agents for cancer therapy gives insight for further evaluations. However, there are some critical points that may affect the entering of flavonoids as active cytotoxic phytochemicals in the clinical phase. Issues such as the abundance of active species in nature, the methods of extraction and purification, solubility, pharmacokinetic profile, presence of the chiral moieties, method of synthesis, and structure modification may limit the entry of a selected compound for use in humans. Although plenty of basic evidence exists for cytotoxic/antitumor activity of the versatility of flavonoids for entry into clinical trials, the above-mentioned concerns must be considered.

CONCLUSION

This review is an effort to introduce cytotoxic natural flavonoids (IC50< 10 µM) that may have the potential to be used against various tumor cells. Also, active constituents, molecular mechanisms, and related clinical trials have been discussed as well as the limitations and challenges of using flavonoids in clinic.

Abyssinone V, a prenylated flavonoid isolated from the stem bark of Erythrina melanacantha increases oxidative stress and decreases stress resistance in Caenorhabditis elegans

OBJECTIVES

Recent studies showed that distinct extracts of Erythrina species used in the traditional medicine of sub-Saharan Africa are protective against stress conditions. However, the underlying molecular mechanisms as well as relevant compounds remain unclear.

METHODS

We used the model organism Caenorhabditis elegans to investigate compounds isolated from the stem bark of Erythrina melanacantha (abyssinone V (1), abyssinon-4'O-methylether (2), sigmoidin B-4'O-methylether (3), glabranin (4), 8-prenylnaringenin (5), citflavanone (6), exiguaflavanone (7) and homoeriodictyol (8)). Antioxidative capacity in vitro (trolox equivalent antioxidative capacity assay) and modulation of oxidative stress in vivo (2', 7'-dichlorofluorescein assay) were investigated; stress resistance was analysed using the nucleic acid stain SYTOX green.

KEY FINDINGS

None of the prenylated flavonoids caused protection against thermal stress; in contrast, most of the compounds (1, 4, 5, 8) decreased stress resistance. None of the compounds decreased the accumulation of reactive oxygen species, but abyssinone V (1) caused an increase in oxidative stress. In line with these results, none of these compounds showed radical-scavenging effects in vitro.

CONCLUSIONS

The stem bark of E. melanacantha contains various prenylated flavonoids, but no compound protected C. elegans against stress conditions. In contrast, abyssinone V increases oxidative stress and reduces stress resistance in this model organism.

Bioactive carbazole and quinoline alkaloids from Clausena dunniana

Nine undescribed carbazole and quinoline alkaloids, named dunnines A-E, and 14 known analogues were isolated from the leaves and stems of Clausena dunniana. Their structures were elucidated on the basis of comprehensive analysis of NMR and HRMS spectroscopic data, and the absolute configurations were assigned via comparison of their specific rotations and calculated and experimental ECD data. (±)-Dunnines A-C and (±)-clausenawalline A are four pairs of biscarbazole atropisomers and (±)-dunnine D is a pair of dihydropyranocarbazole enantiomers. They were separated by chiral HPLC to obtain the optically pure compounds. Three compounds showed weak inhibitory effects on nitric oxide production stimulated by lipopolysaccharide in BV-2 microglial cells (IC₅₀ > 50 μM); five compounds could significantly promote insulin secretion in HIT-T15 cell line (1.9-3.1-fold of the control, p < 0.01) at 40 μM, and nine compounds could inhibit the apoptosis of PC12 cell induced by 6-hydroxydopamine with IC₅₀ values in the range of 10.9-47.2 μM.

Auriculasin-induced ROS causes prostate cancer cell death via induction of apoptosis

Recent studies have demonstrated that natural agents targeting the accumulation of reactive oxygen species (ROS) that selectively kill, leaving normal cells undamaged, can suppress prostate cancer. Here, we show that auriculasin, derived from Flemingia philippinensis, induces significant cell death and apoptosis via ROS generation in prostate cancer cells. Auriculasin treatment resulted in selective apoptotic cell death in LNCaP prostate cancer cells, characterized by DNA fragmentation, accumulation of sub-G1 cell population, cleavage of poly (ADP-ribose) polymerase (PARP), regulation of Bax/Bcl-2 ratio, increase of cytosolic apoptosis-inducing factor (AIF) and endonuclease G (EndoG), in addition to inhibiting tumor growth in a xenograft mouse model. Interestingly, auriculasin-induced apoptosis did not result in caspase-3, -8, and -9 activations. We found that auriculasin treatment decreased phosphorylation of AKT/mTOR/p70s6k in a dose- and time-dependent manner. Further, cellular ROS levels increased in LNCaP cells treated with auriculasin and blocking ROS accumulation with ROS scavengers resulted in inhibition of auriculasin-induced PARP cleavage, AIF increase, upregulation of Bax/Bcl-2 ratio, and decrease in AKT/mTOR phosphorylation. Taken together, these data suggest that auriculasin targets ROS-mediated caspase-independent pathways and suppresses PI3K/AKT/mTOR signaling, which leads to apoptosis and decreased tumor growth.

Protein tyrosine phosphatase 1B inhibitors as antidiabetic agents - A brief review

Diabetes mellitus and obesity are one of the most common health issues spread throughout world and raised the medical attention to find the new effective agents to treat these disease state. Occurrence of the drug resistance to the insulin and leptin receptor is also challenging major issues. The molecules that can overcome this resistance problem could be effective for the treatment of both type II diabetes and obesity. Protein Tyrosine Phosphatase (PTP) has emerged as new promising targets for therapeutic purpose in recent years. Protein Tyrosine Phosphatase 1B (PTP 1B) act as a negative regulator of insulin and leptin receptor signalling pathways. Several approaches have been successfully applied to find out potent and selective inhibitors. This article reviews PTP 1B inhibitors; natural, synthetic and semi-synthetic that showed inhibition towards enzyme as a major target for the management of type II diabetes. These studies could be contributing the future development of PTP 1B inhibitors as drugs.

Exploring the anti-breast cancer potential of flavonoid analogs

In the course of our search for new antitumor agents for breast cancer, novel flavone derivatives were synthesized, characterized and examined for their antitumor activities against breast cancer cell lines.