Cytotoxic xanthones from the roots of Mesua ferrea L

Naturally Occurring Xanthones; Biological Activities, Chemical Profiles and In Silico Drug Discovery

Xanthones are widely distributed polyphenols, present commonly in higher plants; Garcinia, Calophyllum, Hypericum, Platonia, Mangifera, Gentiana and Swertia. Xanthone tricyclic scaffold is able to interact with different biological targets, showing antibacterial and cytotoxic effects, as well as potent effects against osteoarthritis, malaria, and cardiovascular diseases. Thus, in this article we focused on pharmacological effects, applications and preclinical studies with the recent updates of xanthon´s isolated compounds from 2017-2020. We found that only α-mangostin, gambogic acid, and mangiferin, have been subjected to preclinical studies with particular emphasis on the development of anticancer, diabetes, antimicrobial and hepatoprotective therapeutics. Molecular docking calculations were performed to predict the binding affinities of xanthone-derived compounds against SARS-CoV-2 M^pro. According to the results, cratoxanthone E and morellic acid demonstrated promising binding affinities towards SARS-CoV-2 M^pro with docking scores of -11.2 and -11.0 kcal/mol, respectively. Binding features manifested the capability of cratoxanthone E and morellic acid to exhibit nine and five hydrogen bonds, respectively, with the key amino acids of the M^pro active site. In conclusion, cratoxanthone E and morellic acid are promising anti-COVID-19 drug candidates that warrant further detailed in vivo experimental estimation and clinical assessment.

Cytotoxic xanthones from Garcinia pedunculata fruits

Eight previously undescribed and seven known xanthones were isolated from the fruits of Garcinia pedunculata Roxb. The structures were identified by a variety of spectroscopic methods as well as by comparison with the literature. The isolates showed appreciable cytotoxicity against three human tumor cell lines (HepG2, A549, and MCF-7). Pedunculaxanthone G exhibited inhibitory activities with IC50 values of 12.41, 16.51, and 15.45 μM against the cancer cell lines and induced cell apoptosis in HepG2 cells.

Cytotoxic 4-phenylcoumarins from the flowering buds of Mesua ferrea

Eleven 4-phenylcoumarins including three new 4-phenylcoumarins, mesuaferols A-C (1-3), together with eight known 4-phenylcoumarins (4-11) have been isolated from the flowering buds of Mesua ferrea. Their structures were elucidated via UV, IR, HR-ESI-MS, and NMR spectral data. Compound 9 showed moderate cytotoxic activity toward MDA-MB-231, MCF-7, HepG2 and HeLa cell lines with IC50 values of 13.68 ± 1.36 μM, 9.27 ± 1.84 μM, 21.06 ± 1.95 μM, and 7.26 ± 1.68 μM, respectively, and other compounds showed weak cytotoxicity.

The Effect of Ethanol Extract from Mesua ferrea Linn Flower on Alzheimer's Disease and Its Underlying Mechanism

The effects of Mesua ferrea Linn flower (MFE) extract on the pathogenic cascade of Alzheimer's disease (AD) were determined by an in vitro and cell culture model in the search for a potential candidate for the treatment of AD. The 2,2'-azino-bis-3-ethylbenzthiazoline-6-sulphonic acid (ABTS) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay exhibited that the MFE extract had antioxidant activities. According to the Ellman and the thioflavin T method's result, the extracts could inhibit acetylcholinesterase and β-amyloid (Aβ) aggregation. Studies on neuroprotection in cell culture found that the MFE extract could reduce the death of human neuroblastoma cells (SH-SY5Y) caused by H₂O₂ and Aβ. Western blot analysis exhibited that the MFE extract alleviated H₂O₂-induced neuronal cell damage by downregulating the pro-apoptotic proteins, including cleaved caspase-3, Bax, and by enhancing the expression of anti-apoptotic markers including MCl₁, BCl_xl, and survivin. Moreover, MFE extract inhibited the expression of APP, presenilin 1, and BACE, and increased the expression of neprilysin. In addition, the MFE extract could enhance scopolamine-induced memory deficit in mice. Overall, results showed that the MFE extract had several modes of action related to the AD pathogenesis cascade, including antioxidants, anti-acetylcholinesterase, anti-Aβ aggregation, and neuroprotection against oxidative stress and Aβ. Therefore, the M. ferrea L. flower might be a possibility for further development as a medication for AD.

Investigations of specialised metabolites of endophyte Diaporthe destruens hosted in Illigera orbiculata C. Y. Wu

A chemical investigation of the endophytic fungus Diaporthe destruens from the Hernandiaceae plant Illigera orbiculata C. Y. Wu collected from southern Yunnan Province, China, led to the isolation of six undescribed compounds, including two azaphilone analogs, which are a pair of epimers (13R-hydroxy-chermesinone A and 13S-hydroxy-chermesinone A); a pyrrole derivative (1-(4-(methoxymethyl)-1H-pyrrol-3-yl)ethan-1-one); an isoindolone derivative (4-hydroxy-6-methoxyisoindolin-1-one); a benzylbenzene derivative (destruensine A) and a conjectural fragment of polyketide ((2R,4R)-2-(methoxymethyl)pentane-1,4-diol) along with nine known compounds. Their structures were elucidated by spectroscopic methods and HRESIMS, and the absolute configurations were further confirmed by electronic circular dichroism (ECD) and chemical derivatization. The antimicrobial activities, anti-acetylcholinesterase activities, antiproliferation, and NO production inhibitory effects of compounds 1-15 were evaluated.

Exploring in vitro anti-proliferative and anti-inflammatory activities of Prasachandaeng remedy, and its bioactive compounds

Background

Prasachandaeng (PSD) remedy has been empirically used in Thai traditional medicine to treat fever in bile duct and liver and cancer patients through Thai folk doctors. However, there have been no scientific reports on the bioactive compounds and bioactivities related to inflammation-associated carcinogenesis or cytotoxicity against cancer cell lines. In this study, we investigated the chemical content of the remedy, and evaluated its cytotoxic activity against two cancer cell lines in comparison with a non-cancerous cell line and determined tumor necrosis factor-alpha (TNF-α) production in a murine macrophage cell line (RAW 264.7) to evaluate anti-inflammatory activity. A novel HPLC method was used for quality control of its chemical content.

Methods

Pure compounds from the EtOH extract of D. cochinchinensis were isolated using bioassay-guided fractionation and chemical content of the PSD remedy was determined using HPLC. The cytotoxic activity against the hepatocarcinoma cell line (HepG2) and cholangiocarcinoma cell line (KKU-M156), in comparison with non-cancerous cell line (HaCaT), were investigated using antiproliferative assay (SRB). The anti-inflammatory activity measured by TNF-α production in RAW 264.7 was determined using ELISA.

Results

All crude extracts and isolated compounds exhibited significant differences from vincristine sulfate (^****p < 0.0001) in their cytotoxic activity against HepG2, KKU-M156, and HaCaT. The PSD remedy exhibited cytotoxic activity against HepG2 and KKU-M156 with IC₅₀ values of 10.45 ± 1.98 (SI = 5.3) and 4.53 ± 0.74 (SI = 12.2) µg/mL, respectively. Some constituents from C. sappan, D. cochinchinensis, M. siamensis, and M. fragrans also exhibited cytotoxic activity against HepG2 and KKU-M156, with IC₅₀ values less than 10 µg/mL. The isolated compounds, i.e., Loureirin B (1), 4-Hydroxy-2,4’-dimethoxydihydrochalcone (2), and Eucomol (3) exhibited moderate cytotoxicity against two cancer cell lines. None of the crude extracts and isolated compounds showed cytotoxicity against HaCaT. D. cochinchinensis and PSD remedy exhibited higher anti-inflammatory activity measured as TNF-α production than acetaminophen.

Conclusion

The findings provide evidence of bioactivity for EtOH extracts of PSD remedy and the isolated compounds of D. Cochinchinensis. The results consistent the use clinical activity and use of PSD remedy as a antipyretic treatment for liver and bile duct cancer patients by Thai traditional practitioners.

Phloroglucinol-meroterpenoids from the leaves of Eucalyptus camaldulensis Dehnh

Fourteen undescribed phloroglucinol-meroterpenoids, namely eucalypcamals A-N, were isolated from a CH₂Cl₂ extract of the leaves of Eucalyptus camaldulensis Dehnh. In addition, from the same extract, twelve known phloroglucinols, three known flavonoids, and four known phenolic compounds were also isolated. The structures of the undescribed compounds were analyzed by 1D and 2D nuclear magnetic resonance (NMR) spectroscopy, and high resolution electrospray ionization mass spectrometry (HRESIMS). The assignments of the absolute configurations were performed by comparing the experimental electronic circular dichroism (ECD) data with the calculated values. Eucalyprobusal E was found to be cytotoxic against HCT116, Jurkat, and MDA-MB-231 cell lines with IC₅₀ values of 17.6, 9.44, and 17.9 μM, respectively. Eucalrobusone F exhibited antibacterial activity against methicillin-resistant S. aureus (MRSA) and S. aureus with minimum inhibitory concentration/minimum bactericidal concentration (MIC/MBC) values of 4/4 μg/mL while euglobal Ia₁ showed antifungal activity with MIC/MFC values of 16/16 μg/mL.

Antiallergic Properties of Biflavonoids Isolated from the Flowers of Mesua ferrea Linn

The methanolic extract from the flowers of Mesua ferrea Linn. (Calophyllaceae) showed significant hyaluronidase inhibitory activity. Following a bioassay-guided separation of the extract, two biflavonoids, viz., mesuaferrone-A (1) and mesuaferrone-B (2), were isolated, along with ten flavonoids (3–12), two xanthones (13 and 14), three triterpenes (15–17), a phenylpropanoid (18), and five aromatics (19–24). Among the isolates, 1 and 2 (IC50 = 51.1 µM and 54.7 µM, respectively) exhibited hyaluronidase inhibitory activity equivalent to that of the commercially available antiallergic agents disodium cromoglycate (64.8 μM) and ketotifen fumarate (76.5 μM). These biflavonoids (1 and 2) are 8-8″ linked dimers that are composed of naringenin (1a) or apigenin (3), with their corresponding monomers lacking inhibitory activity (IC50 > 300 μM). In addition, 1 and 2 (IC50 = 49.4 µM and 49.2 µM, respectively) inhibited the release of β-hexosaminidase, which is a marker of antigen-IgE-mediated degranulation, in rat basophilic leukemia (RBL-2H3) cells. These inhibitory activities were more potent than those of the antiallergic agents tranilast and ketotifen fumarate (IC50 = 282 μM and 158 μM, respectively), as well as one of the corresponding monomers (1a; IC50 > 100 μM). Nonetheless, these effects were weaker than those of the other monomer (3; IC50 = 6.1 μM).

Anti-Acne Vulgaris Potential of the Ethanolic Extract of Mesua ferrea L. Flowers

Acne vulgaris is a common chronic inflammatory skin disease. In the present study, we reported the anti-acne vulgaris effect of the Mesua ferrea (M. ferrea) flower extract. The extract was evaluated for three anti-acne-causing bacteria properties including Cutibacterium acnes (C. acnes), Staphylococcus epidermidis (S. epidermidis) and Staphylococcus aureus (S. aureus). The results indicated that the M. ferrea flower extract could be considered as the bactericidal agent against S. epidermidis and S. aureus with MIC values of 0.78 and 6.25 mg mL−1 and MBC values of 1.56 and 12.50 mg mL−1 and the bacteriostatic agent against C. acnes with MIC and MBC values of 3.12 and 25.00 mg mL−1, respectively. The extract at a concentration of 25 µg mL−1 also presented potent anti-inflammatory activity with a significant decrease of nitric oxide (NO) and tumor necrosis factor (TNF)-α productions in RAW 264.7 macrophage cells stimulated by LPS. In addition, the extract showed moderate to weak anti-oxidative capacities against DPPH, ABTS, FRAP and NO assays and also showed weak anti-tyrosinase activity. M. ferrea flower extract may serve as the alternative natural anti-acne formulations.

An Update on the Anticancer Activity of Xanthone Derivatives: A Review

The annual number of cancer deaths continues increasing every day; thus, it is urgent to search for and find active, selective, and efficient anticancer drugs as soon as possible. Among the available anticancer drugs, almost all of them contain heterocyclic moiety in their chemical structure. Xanthone is a heterocyclic compound with a dibenzo-γ-pyrone framework and well-known to have "privileged structures" for anticancer activities against several cancer cell lines. The wide anticancer activity of xanthones is produced by caspase activation, RNA binding, DNA cross-linking, as well as P-gp, kinase, aromatase, and topoisomerase inhibition. This anticancer activity depends on the type, number, and position of the attached functional groups in the xanthone skeleton. This review discusses the recent advances in the anticancer activity of xanthone derivatives, both from natural products isolation and synthesis methods, as the anticancer agent through in vitro, in vivo, and clinical assays.

Xanthone: A Promising Antimycobacterial Scaffold

BACKGROUND

Tuberculosis (TB) is one of the infectious diseases associated with high rate of morbidity and mortality and still remains one of the top-ten leading causes of human death in the world. The development of new anti-TB drugs is mandatory due to the existence of latent infection as well as the expansion of the resistant Mycobacterium tuberculosis (MBT) strains. Xanthones encompass a wide range of structurally diverse bioactive compounds, obtained either naturally or through chemical synthesis. There is a growing body of literature that recognizes the antitubercular activity of xanthone derivatives.

OBJECTIVE

The objective of this review is to highlight the main natural sources along with the critical design elements, structure-activity relationships (SARs), modes of action and pharmacokinetic profiles of xanthone-based anti-TB compounds.

METHODS

In the present review, the anti-TB activity of xanthones reported in the literature from 1972 to date is presented and discussed.

RESULTS

Exploration of xanthone scaffold led to the identification of several members of this class having superior activity against both sensitive and resistant MBT strains with distinctive mycobacterial membrane disrupting properties. However, studies regarding their modes of action, pharmacokinetic properties and safety are limited.

CONCLUSION

Comprehendible data and information are afforded by this review and it would certainly provide scientists with new thoughts and means which will be conducive to design and develop new drugs with excellent anti-TB activity through exploration of xanthone scaffold.

Ethnopharmacological analysis from Thai traditional medicine called prasachandaeng remedy as a potential antipyretic drug

ETHNOPHARMACOLOGICAL RELEVANCE

Prasachandaeng (PSD) remedy is a famous antipyretic drug for adults and children in Thai traditional medicine used and is described in Thailand's National List of Essential Medicine. Relationship between the taste of this herbal medicine, ethnopharmacological used and its pharmacological properties was reviewed.

AIMS OF STUDY

Since there has been no scientific report on the antipyretic activity of PSD, aim of this study was to investigate the efficacy related antipyretic drug of the remedy and its 12 herbal ingredients. It involved quality evaluation of raw materials, extraction of PSD and its ingredients, in vitro evaluation of their inhibitory activities on fever mediators, i.e. NO and PGE₂ production in murine macrophage (RAW 264.7) cell line stimulated by lipopolysaccharide, and its stability study of the 95% ethanolic extract of PSD remedy.

MATERIALS AND METHODS

PSD remedy was extracted by maceration with 50% and 95% ethanol (PSD50 and PSD95), by decoction with distilled water (PSDW), and hydrolysis of PSDW with 0.1 N HCl (PSDH). The 12 plant ingredients were extracted with 95% ethanol. Quality evaluation of PSD ingredients was performed according to the standard procedures for the quality control of herbal materials. The inhibitory activity on nitric oxide production was determined by the Griess reaction and the inhibition of prostaglandin E₂ production was determined using the ELISA test kit.

RESULTS

PSD ingredients passed the quality standard stipulated for herbal materials. PSD95 exhibited the highest inhibitory activities on the production of NO and PGE₂ with the IC₅₀ values of 42.40 ± 0.72 and 4.65 ± 0.76 μg/mL, respectively. A standard drug acetaminophen (ACP) exhibited inhibition of NO and PGE₂ production with the IC₅₀ values of 99.50 ± 0.43 and 6.110 ± 0.661 μg/mL, respectively. The stability study was suggested two years shelf-life of PSD95. This is the first report on the activity related antipyretic activity of PSD remedy and its ingredients against two fever mediators, NO and PGE₂.

CONCLUSION

The results suggested that the 95% ethanolic extracts of PSD remedy and some of its ingredients, were better than ACP in reducing fever. PSD should be further studied using in vivo models and clinical trials to support its use as an antipyretic drug in Thai traditional medicine.

Xanthones and Cancer: from Natural Sources to Mechanisms of Action

Xanthones are a class of heterocyclic natural products that have been widely studied for their pharmacological potential. In fact, they have been serving as scaffolds for the design of derivatives focusing on drug development. One of the main study targets of xanthones is their anticancer activity. Several compounds belonging to this class have already demonstrated cytotoxic and antitumor effects, making it a promising group for further exploration. This review therefore focuses on recently published studies, emphasizing their natural and synthetic sources and describing the main mechanisms of action responsible for the anticancer effect of promising xanthones.