Phenolic Glycosides with antiproteasomal activity from Centaurea urvillei DC. subsp. urvillei

Biological Activities of the Fruit Essential Oil, Fruit, and Root Extracts of Ferula drudeana Korovin, the Putative Anatolian Ecotype of the Silphion Plant

In the present study, preliminary phytochemical investigations were performed on the fruit essential oil and antioxidant-rich methanolic extracts of the fruits and roots of Ferula drudeana, the putative Anatolian ecotype of the Silphion plant, to corroborate its medicinal plant potential and identify its unique characteristics amongst other Ferula species. The essential oil from the fruits of the endemic species Ferula drudeana collected from Aksaray was analyzed by GC and GC/MS. The main components of the oil were determined as shyobunone (44.2%) and 6-epishyobunone (12.6%). The essential oil of the fruits and various solvent extracts of the fruits and roots of F. drudeana were evaluated for their antibacterial and anticandidal activity using microbroth dilution methods. The essential oil of the fruits, methanol, and methylene chloride extracts of the fruits and roots showed weak to moderate inhibitory activity against all tested microorganisms with MIC values of 78-2000 µg/mL. However, the petroleum ether extract of the roots showed remarkable inhibitory activity against Candida krusei and Candida utilis with MIC values of 19.5 and 9.75 µg/mL, respectively. Furthermore, all the samples were tested for their antioxidant activities using DPPH^• TLC spot testing, online HPLC-ABTS screening, and DPPH/ABTS radical scavenging activity assessment assays. Methanolic extracts of the fruits and roots showed strong antioxidant activity in both systems.

Feature-Based Molecular Networking for the Exploration of the Metabolome Diversity of Common Egyptian Centaurea Species in Relation to Their Cytotoxic Activity

Centaurea is a genus compromising over 250 herbaceous flowering species and is used traditionally to treat several ailments. Among the Egyptian Centaurea species, C. lipii was reported to be cytotoxic against multidrug-resistant cancer cells. In this context, we aimed to explore the metabolome of C. lipii and compare it to other members of the genus in pursuance of identifying its bioactive principles. An LC-MS/MS analysis approach synchronized with feature-based molecular networks was adopted to offer a holistic overview of the metabolome diversity of the Egyptian Centaurea species. The studied plants included C. alexandrina, C. calcitrapa, C. eryngioides, C. glomerata, C. lipii, C. pallescens, C. pumilio, and C. scoparia. Their constitutive metabolome showed diverse chemical classes such as cinnamic acids, sesquiterpene lactones, flavonoids, and lignans. Linking the recorded metabolome to the previously reported cytotoxicity identified sesquiterpene lactones as the major contributors to this activity. To confirm our findings, bioassay-guided fractionation of C. lipii was adopted and led to the isolation of the sesquiterpene lactone cynaropicrin with an IC₅₀ of 1.817 µM against the CCRF-CEM leukemia cell line. The adopted methodology highlighted the uniqueness of the constitutive metabolome of C. lipii and determined the sesquiterpene lactones to be the responsible cytotoxic metabolites.

Arbutin: Occurrence in Plants, and Its Potential as an Anticancer Agent

Arbutin, a hydroquinone glucoside, has been detected in ca. 50 plant families, especially in the plants of the Asteraceae, Ericaceae, Proteaceae and Rosaceae families. It is one of the most widely used natural skin-whitening agents. In addition to its skin whitening property, arbutin possesses other therapeutically relevant biological properties, e.g., antioxidant, antimicrobial and anti-inflammatory, as well as anticancer potential. This review presents, for the first time, a comprehensive overview of the distribution of arbutin in the plant kingdom and critically appraises its therapeutic potential as an anticancer agent based on the literature published until the end of August 2022, accessed via several databases, e.g., Web of Science, Science Direct, Dictionary of Natural Products, PubMed and Google Scholar. The keywords used in the search were arbutin, cancer, anticancer, distribution and hydroquinone. Published outputs suggest that arbutin has potential anticancer properties against bladder, bone, brain, breast, cervix, colon, liver, prostate and skin cancers and a low level of acute or chronic toxicity.

Bioprospecting the Metabolome of Plant Urtica dioica L.: A Fast Dereplication and Annotation Workflow in Plant Metabolomics

Plants have a pivotal role in ethnopharmacology, and their preparations are in use globally. However, getting down to the structure requires an effective workflow and mostly requires a time-consuming isolation process. Although bioassay-guided approaches are widely popular, they face a massive problem of rediscovery in recent times, especially in plant metabolomics. Mass spectrometry (MS)-based approach incorporated molecular networking via Global Natural Product Social Molecular Networking (GNPS) is considered here for the benefit of the fast screening of secondary metabolites. This study uses direct crude extracts obtained from various parts of the Urtica dioica plant for the characterization of secondary metabolites. The crude extract of the plant initially displayed promising antioxidant and anti-diabetic activities. Then, we employed mass spectrometry-based dereplication to identify the phytochemical components in the extracts. This led to the discovery of 7 unknown and 17 known secondary metabolites, which were further verified with the SIRIUS 4 platform, a computational tool for the annotation of compounds using tandem MS data. On the other hand, chasing the antioxidant activity of methanolic extract of U. dioica leaves, we employed a bioassay-guided isolation approach. With this method, we isolated and characterized compound 13, a known molecule, which possessed strong antioxidant activity without showing much toxicity in the brine shrimp lethality test at the test concentration of 1 mg/mL. With our results, we advocate the MS-based approach as a good starting point for the dereplication of compounds from the complex crude extracts of plants.

A Review on Antidiabetic Activity of Centaurea spp.: A New Approach for Developing Herbal Remedies

Objective

Diabetes mellitus (DM) is a long-life metabolic disorder, characterized by high blood glucose levels. The hyperglycemic condition generally leads to irreversible nerve injury and vascular damage. Among different types of diabetes, type 2 is more common and has spread all over the world. Although various therapeutic approaches have been developed to control type 2 DM, regulating blood glucose levels has still remained a controversial challenge for patients. Also, most prescription drugs cause different side effects, such as gastrointestinal disorders. Thus, developing novel and efficient antidiabetic agents possessing fewer adverse effects is in high demand.

Method

The literature was comprehensively surveyed via search engines such as Google Scholar, PubMed, and Scopus using appropriate keywords.

Results

Medicinal plants, both extracts and isolated active components, have played a significant role in controlling the blood glucose levels. Good-to-excellent results documented in the literature have made them a precious origin for developing and designing drugs and supplements against DM. Centaurea spp. have been traditionally used for controlling high blood glucose levels. Also, the antidiabetic properties of different species of Centaurea have been confirmed in recent studies through in vitro assays as well as in vivo experiments.

Conclusion

Potent results encouraged us to review their efficacy to open a new horizon for development of herbal antidiabetic agents.

Evaluation of cell protection by Psephellus pyrrhoblepharus (Boiss.) Wagenitz extracts in MPP+-induced dopaminergic cell damage

Neurodegenerative diseases affect millions of people. Major reasons behind the onset and progression of these diseases are still under investigation. Therefore, any approach that would treat/prevent progression is important. In this study, we aimed to investigate the potential protective effects of Psephellus pyrrhoblepharus (Boiss.) Wagenitz extracts in MPP⁺-induced dopaminergic cell damage and compare the effectiveness of different extracts (methanol:water (1:1), chloroform and n-hexane). The cells were pretreated with four different concentrations (10, 50, 100, and 200 µg/ml) of methanol:water (1:1), chloroform and n-hexane extracts of P. pyrrhoblepharus following MPP⁺ treatment for 12 or 24 h. The changes in cell viability were determined using the MTT assay. Additionally, antioxidant activities and total phenolic/flavonoid contents of the extracts were determined with radical scavenging capacity, Folin-Ciocalteu and aluminum chloride assays, respectively. The extracts at selected concentrations were found to be protective in a dose-dependent manner at 12 and 24 h. Nevertheless, the methanol extract of the plant showed the highest protection both at 100 and 200 µg/ml (115.13%±3.98, 121.87%±1.66; p < 0.05) against dopaminergic damage at 24 h. The results showed that selected concentrations were not toxic and did not affect cell proliferation rate. Besides, the chloroform extract was found to have higher antioxidant activity than the other extracts (p < 0.05). The total phenolic and total flavonoid contents were found consistent with antioxidant activities. Our findings support the neuroprotective and antioxidant potential of P. pyrrhoblepharus. However, further studies on identifying the presence of chemicals in P. pyrrhoblepharus extracts which are responsible for protection should be carried out to confirm their therapeutic potential.

Centaurea albonitens extract enhances the therapeutic effects of Vincristine in leukemic cells by inducing apoptosis

Drug-induced toxicities and dose-related side effects are the major challenges in the conventional cancer therapy by the chemo drugs. On the other hand, herbal derivatives have obtained a great research interest in the field of therapeutic applications because of their more favorable specifications including less toxicity, cost-effective and more physiologically compatible than the chemical drugs. For this purpose, we evaluated methanolic extract prepared from Centaurea albonitens Turrill alone and in combination with Vincristine (VCR) for its potential cytotoxic effects in NALM-6, REH, NB4 and KMM-1 cell lines by using the various approaches. Centaurea genus is one of the current medicinal plants, which has used in traditional medicine, However, there are rare studies to examine its anticancer properties against hematologic malignant cells. In this study, we demonstrated Centaurea albonitens extract (CAE) induces cytotoxicity through G0/G1 phase arrest followed by apoptosis in a dose- and time- dependent manner, although with varying efficiency. Interestingly, normal cells didn't exhibit significant cytotoxicity after CAE treatment. Moreover, we found that low dose of CAE enhances anti-cancer effects of VCR in pre-B ALL cell lines (NALM-6 and REH). Further investigations validated synergistic anticancer activities of VCR and CAE through inducing apoptosis without significant cell cycle arrest. Taken together, our results demonstrated for the first time that the methanolic extract of Centaurea albonitens can be considered as a potential anticancer agent and/or an enhancer of chemotherapeutic sensitivity of VCR.

Specialized metabolites from the aerial parts of Centaurea polyclada DC

The genus Centaurea L. (Asteraceae) is represented by 200 taxa in the flora of Turkey and several Centaurea species are used as herbal remedies against different conditions. Previous phytochemical investigations on this genus generally revealed the isolation of sesquiterpene lactones and flavonoid derivatives. In our continuous search on Centaurea genus, a phytochemical study was performed on Centaurea polyclada DC., an endemic of West Anatolia. Previously undescribed two sesquiterpene-amino acid conjugates, an elemane and an eudesmane derivative were isolated from the aerial parts of Centaurea polyclada, together with eight known compounds; two elemane derivatives, three flavonoids, a lignan, a phenolic glucoside and a phenylpropanoid glucoside. Structural elucidation of the compounds was based on spectroscopic evidence, including 1D and 2D NMR and high-resolution mass spectrometry, chemical degradation results and reference data comparison. Sesquiterpene-amino acid conjugates are representatives of an unusual group of sesquiterpenes, and elemane-amino acid conjugates are herein reported for the first time in nature.

Crystal structure and computational study of 3,4-dihydroxy-3-hydroxymethyl-9-methyl-6-methylidene-3a,4,5,6,6a,9,9a,9b-octahydroazuleno[4,5-b]furan-2,8(3H,7H)-dione

The cyclo­pentane ring displays a twist conformation and the γ-lactone ring has an envelope conformation while the cyclo­heptane ring adopts a twist-chair conformation. O—H⋯O hydrogen bonds link the mol­ecules, forming a three-dimensional network. A comparison between the structural parameters obtained by X-ray structure analysis and theoretical calculations give a satisfactory agreement.

In the mol­ecule of title compound, C₁₅H₂₀O₆, also known as cynarinin A, the cyclo­pentane ring having twist conformation and a γ-lactone ring assuming an envelope conformation are trans- and cis-fused, respectively, to a cyclo­heptane ring adopting a twist-chair conformation. In the crystal, O—H⋯O hydrogen bonds link neighbouring mol­ecules, forming a three-dimensional network. Theoretical calculations of the mol­ecular structure using the CNDO approximation and MOPAC PM3 geometry optimization are in satisfactory agreement with the results of the X-ray structure analysis.

Antioxidant activity of phenolics in leaves of three red pepper (Capsicum annuum) cultivars

The antioxidant properties and phenolic profiles were first investigated in this paper on the leaves of three red pepper cultivars, Blackcuban (BCPL), Hongjinju (HPL), and Yeokgang-hongjanggun (YHPL). Of the ethanol extract of the three cultivars, BCPL showed potent antioxidant activities against the 1,1-diphenyl-2-picrylhydrazyl radical (DPPH) and the 2,2-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical. Nine antioxidative compounds from the red pepper leaves were isolated and identified as one polyamine phenolic conjugate, N-caffeoylputrescine (1); three chlorogenic acid derivatives, 5-O-caffeoylquinic acid (2), 5-O-caffeoylquinic acid methyl ester (4), and 5-O-caffeoylquinic acid butyl ester (9); one anthocyanin, delphinidin-3-[4-trans-coumaroyl-l-rhamnosyl(1→6)glucopyranoside]-5-O-glucopyranoside (3); and four flavone glycosides, luteolin-7-O-apiofuranosyl(1→2)glucopyranoside (5), luteolin-7-O-glucopyranoside (6), apigenin 7-O-apiofuranosyl(1→2)glucopyranoside (7), apigenin-7-O-glucopyranoside (8). 1 and 3 had the greatest potential for radical-scavenging activity and HepG2 cells protecting effect against oxidative stress. BCPL exhibited the highest content of 1 and 3. Of the three cultivars BCPL may be considered a good source of antioxidants.

Flavonoids in subtribe Centaureinae (Cass.) Dumort. (tribe Cardueae, Asteraceae): distribution and (13)C-NMR spectral data

This review reports the occurrence of flavonoids in subtribe Centaureinae of Asteraceae family. It extensively covers the literature up to 2010 and collects all available (13)C-NMR data.