Flavanone glycosides from Miconia trailii

Health functions and related molecular mechanisms of Miconia genus: A systematic review

The Miconia genus is traditionally used in folk medicine in Brazil and other tropical American countries and is represented by 282 species in this region. It is a multifaceted genus of medicinal plants widely used to treat rheumatoid arthritis (RA), pain, inflammatory diseases, and many more therapeutic applications. In the present study, we systematically identify and discuss the literature on in vivo and in vitro studies focusing on the therapeutic potentials and related molecular mechanisms of the Miconia genus. The review also assessed phytochemicals and their pharmacological properties and considered safety concerns related to the genus. Literature searches to identify studies on the Miconia genus were carried out through four main electronic databases, namely PubMed, Embase, Scopus, and Web of Science limited to Medical Subjects Headings (MeSH) and Descriptores en Ciencias de la Salud (DCS) (Health Sciences Descriptors) to identify studies published up to December 2022. The relevant information about the genus was gathered using the keywords 'Miconia', 'biological activities', 'therapeutic mechanisms', 'animal model, 'cell-line model', 'antinociceptive', 'hyperalgesia', 'anti-inflammatory', and 'inflammation'. The therapeutic potentials and mechanisms of action of 14 species from genus Miconia were examined in 18 in vitro studies and included their anti-inflammatory, anticancer, analgesic, antibacterial, cytotoxic, mutagenic, antioxidant, anti-leishmanial, antinociceptive, schistosomicidal, and anti-osteoarthritis potentials, and in eight in vivo studies, assessing their analgesic, antioxidant, antinociceptive, and anti-osteoarthritis activities. Some of the main related molecular mechanisms identified are the modulation of cytokines such as IL-1β, IL-6, and TNF-α, as well as the inhibition of inflammatory mediators and prostaglandin synthesis. The limited number of studies showed that commonly available species from the genus Miconia are safe for consumption. Miconia albicans Sw.Triana and Miconia rubiginosa (Bonpl.) DC was the most frequently used species and showed significant efficacy and potential for developing safe drugs to treat pain and inflammation.

Identification of Phytochemicals in Bioactive Extracts of Acacia saligna Growing in Australia

Acacia saligna growing in Australia has not been fully investigated for its bioactive phytochemicals. Sequential polarity-based extraction was employed to provide four different extracts from individual parts of A. saligna. Bioactive extracts were determined using in vitro antioxidant and yeast α-glucosidase inhibitory assays. Methanolic extracts from barks, leaves, and flowers are the most active and have no toxicity against 3T3-L1 adipocytes. Compound isolation of bioactive extracts provided us with ten compounds. Among them are two novel natural products; naringenin-7-O-α-L-arabinopyranoside 2 and (3S*,5S*)-3-hydroxy-5-(2-aminoethyl) dihydrofuran-2(3H)-one 9. D-(+)-pinitol 5a (from barks and flowers), (-)-pinitol 5b (exclusively from leaf), and 2,4-di-t-butylphenol 7 are known natural products and new to A. saligna. (-)-Epicatechin 6, quercitrin 4, and myricitrin 8 showed potent antioxidant activities consistently in DPPH and ABTS assays. (-)-Epicatechin 6 (IC₅₀ = 63.58 μM),D-(+)-pinitol 5a (IC₅₀ = 74.69 μM), and naringenin 1 (IC₅₀ = 89.71 μM) are the strong inhibitors against the α-glucosidase enzyme. The presence of these compounds supports the activities exerted in our methanolic extracts. The presence of 2,4-di-t-butylphenol 7 may support the reported allelopathic and antifungal activities. The outcome of this study indicates the potential of Australian A. saligna as a rich source of bioactive compounds for drug discovery targeting type 2 diabetes.

The Genus Miconia Ruiz & Pav. (Melastomataceae): Ethnomedicinal Uses, Pharmacology, and Phytochemistry

Species of the genus Miconia are used in traditional medicine for the treatment of diseases, such as pain, throat infections, fever, and cold, and they used as depuratives, diuretics, and sedatives. This work reviewed studies carried out with Miconia species, highlighting its ethnomedicinal uses and pharmacological and phytochemical potential. This information was collected in the main platforms of scientific research (PubMed, Scopus, and Web of Science). Our findings show that some of the traditional uses of Miconia are corroborated by biological and/or pharmacological assays, which demonstrated, among other properties, anti-inflammatory, analgesic, antimutagenic, antiparasitic, antioxidant, cytotoxic, and antimicrobial activities. A total of 148 chemical compounds were identified in Miconia species, with phenolic compounds being the main constituents found in the species of this genus. Such phytochemical investigations have demonstrated the potential of species belonging to this genus as a source of bioactive substances, thus reinforcing their medicinal and pharmacological importance.

Seasonal Chemical Evaluation of Miconia chamissois Naudin from Brazilian Savanna

Miconia chamissois Naudin is a species from the Cerrado, which is being increasingly researched for its therapeutic potential. The aim of this study was to obtain a standardized extract and to evaluate seasonal chemical variations. Seven batches of aqueous extracts from leaves were produced for the standardization. These extracts were evaluated for total solids, polyphenol (TPC) and flavonoid content (TFC), vitexin derivative content, antioxidant activity; thin-layer chromatography (TLC), and high-performance liquid chromatography (HPLC) profiles were generated. For the seasonal study, leaves were collected from five different periods (May 2017 to August 2018). The results were correlated with meteorological data (global radiation, temperature, and rainfall index). Using chromatographic and spectroscopic techniques, apigenin C-glycosides (vitexin/isovitexin) and derivatives, luteolin C-glycosides (orientin/isoorientin) and derivatives, a quercetin glycoside, miconioside B, matteucinol-7-O-β-apiofuranosyl (1 → 6) -β-glucopyranoside, and farrerol were identified. Quality parameters, including chemical marker quantification by HPLC, and biological activity, are described. In the extract standardization process, all the evaluated parameters showed low variability. The seasonality study revealed no significant correlations (p < 0.05) between TPC or TFC content and meteorological data. These results showed that it is possible to obtain extracts from M. chamissois at any time of the year without significant differences in composition.

Chemical profile, antioxidant and anti-inflammatory properties of Miconia albicans (Sw.) Triana (Melastomataceae) fruits extract

ETHNOPHARMACOLOGICAL RELEVANCE

Miconia albicans (Sw.) Triana has been widely used in Brazilian popular medicine for the treatment of several diseases. Aerial parts are used as an infusion to treat arthrosis and arthritis, to relieve rheumatic and stomach pains, and intestinal disorders due to its anti-inflammatory, anti-mutagenic anti-nociceptive, digestive and hepatoprotective properties.

AIM OF THE STUDY

This study aimed to characterize the of M. albicans (Sw.) Triana fruits extract (MAFRE) chemical profile and to evaluate its antioxidant, anti-inflammatory and antitumor activities, as well as its toxicity.

MATERIALS AND METHODS

Maceration with methanol as liquid extractor was used to prepare MAFRE. M. albicans (Sw.) Triana fruits chemical composition was characterized by UHPLC-QTOF-MS/MS and GC-FID (fatty acid methyl esters composition from lyophilized fruits). MAFRE antioxidant potential was evaluated in vitro using a combination of assays: Folin-Ciocalteu reducing capacity, DPPH^• and ABTS radical scavenging ability and ferric reducing antioxidant power (FRAP). In vitro antiproliferative activity was investigated in four human tumor cell lines (U251, 786-0, HT29 and MDA-MB-231) while the effect on the non-tumor cell viability was assessed in the VERO cell line using the on-step MTT assay. In addition, in vivo anti-inflammatory effect was assessed by Croton oil-induced ear edema in mice followed by myeloperoxidase (MPO) activity evaluation.

RESULTS

Thirty-five compounds were identified by UHPLC-QTOF-MS/MS. Among it flavonoids derived from quercetin (8), myricetin (1), kaempferol (2), terpenoids (6) and other compounds (18). GC-FID analysis identified and quantified nine fatty acids: palmitic, stearic, arachidic, behenic, elaidic, oleic, eicosenoic, and linoleic acids. The most abundant fatty acids were polyunsaturated fatty acids (5.33 ± 0.17 mg g^-1), followed by saturated fatty acids (2.38 ± 0.07 mg g^-1) and monounsaturated fatty acids (1.74 ± 0.09 mg g^-1). The extract revealed high content of phenolic compounds (43.68 ± 0.50 mg GAE/g of extract), potent antioxidant, and ferrous chelating capacities. Morever, it proved to be non-toxic to the VERO cells, not affecting cells viability (95% of viable cells). No antiproliferative effect against human tumor cell lines were found. Furthermore, MAFRE significantly (p<0.05) reduced ear edema (≈35%) and MPO activity (84.5%) having a statistical effect similar to traditional steroidal and non-steroidal anti-inflammatory drugs.

CONCLUSIONS

Taken together, the results evidenced that M. albicans fruit extract has antioxidant properties, a higher concentration of phenolic compounds, flavonoids, fatty acids, and also topical anti-inflammatory activity with low toxicity of extract on VERO cells. Through the ethnomedicinal study, these findings supporting the popular use of M. albicans, but also highlight that not only aerial parts and leaves deserve attention, but the fruits also have anti-inflammatory proprieties and can be a source of phenolic compounds and other substances with potential health benefices.

Carbon-13 NMR Chemical Shift of Methyl Group: A Useful Parameter for Structural Analysis of C-Methylated Flavonoids

The 13C NMR resonances corresponding to the C-Me group of C-6 and/or C-8 C-methylated-flavonoids absorb between 6.7–10.0 ppm and typically between 6.7–8.7 ppm. A comparative 13C NMR study reflects that the 13C NMR chemical shifts reported for 6-hydroxy-5-methyl-3′,4′,5′-trimethoxyaurone-4-O-α-L-rhamnoside from Pterocarpus santalinus and 8-C-methyl-5,7,2′,4′- tetramethoxyflavanone from Terminalia alata are inconsistent with the assigned structures, and therefore need reconsideration.

Comprehensive characterisation of polyphenols in leaves and stems of three anti-dengue virus type-2 active Brazilian Faramea species (Rubiaceae) by HPLC-DAD-ESI-MS/MS

INTRODUCTION

The methanol (MeOH) leaf extracts of the species Faramea bahiensis, F. hyacinthina and F. truncata (Rubiaceae) have previously shown in vitro non-cytotoxic and anti-dengue virus serotype 2 (DENV2) activities in human hepatocarcinoma cell lineage (HepG2). Chemical studies have led to the isolation of major flavonoids, but quite complex fractions of phenolic compounds still remain.

OBJECTIVE

To complete the study of phenolic compounds in the leaves and to access the presence of these compounds in the stems of these Faramea spp. by online high-performance liquid chromatography-diode array detector-electrospray ionisation tandem mass spectrometry (HPLC-DAD-ESI-MS/MS), as well as to evaluate the in vitro cytotoxic and anti-DENV2 activities of their MeOH stem extracts.

METHODOLOGY

The identification was performed by comparing retention times, UV and mass spectra with those of available standards and by using the mechanisms and fragmentation patterns established in previous studies. The effects of the extracts in DENV2 infected HepG2 cell viability was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The virus titer was quantified by plaque assay.

RESULTS

The study led to the characterisation of 31 phenolic compounds including flavonoid O- and C-glycosides, phenolic acids and one coumarin. The stem extracts from F. hyacinthina and F. bahiensis presented a similar bioactivity to those of their leaves but a loss of cytoprotective activity of F. bahiensis and a higher cytotoxicity of F. truncata were observed.

CONCLUSIONS

This research allowed a detailed phenolic composition of three bioactive Faramea species to be achieved, thus contributing to the study of this genus and providing valuable information for further phytotherapeutic applications.

Antimicrobial and antioxidant activities of triterpenoid and phenolic derivatives from two Cameroonian Melastomataceae plants: Dissotis senegambiensis and Amphiblemma monticola

Background

Antimicrobial resistance is a serious threat against humankind and the search for new therapeutics is needed. This study aims to investigate the antimicrobial and antioxidant activities of ethanol extracts and compounds isolated from Dissotis senegambiensis and Amphiblemma monticola, two Cameroonian Melastomataceae species traditionally used for the treatment of fever, malaria and infectious diseases.

Methods

The plant extracts were prepared by maceration in ethanol. Standard chromatographic and spectroscopic methods were used to isolate and identify fourteen compounds from the two plant species [1–6 (from D. senegambiensis), 3, 4 and 7–14 (from A. monticola)]. A two-fold serial micro-dilution method was used to determine the minimum inhibitory concentration (MIC) against four bacterial strains including two resistant bacterial strains, methicillin resistant S. aureus (MRSA3) and methicillin resistant S. aureus (MRSA4) and three yeast strains.

Results

The fractionation of EtOH extracts afforded fourteen compounds belonging to triterpenoid and phenolic derivatives. The ethanol extracts, compounds 3, 5–8, 10 and the mixture of 10 + 12 were active against all the tested bacterial and fungal species. Compound 7 (MIC = 16–32 μg/mL) and 10 (MIC = 8–16 μg/mL) displayed the largest antibacterial and antifungal activities, respectively. Compounds 7, 10 and the mixture of 10 + 12 showed prominent antibacterial activity against methicillin- resistant S. aureus (MRSA) which is in some cases equal to that of ciprofloxacin used as reference antibacterial drug. Compound 8 also showed high radical-scavenging activities and ferric reducing power when compared with vitamin C and butylated hydroxytoluene used as reference antioxidants. The tested samples were non-toxic to normal cells highlighting their good selectivity.

Conclusions

The result of this investigation reveals the potential of D. senegambiensis and A. monticola as well as the most active compounds in the search for new antimicrobial and antioxidant agents. So, further investigations are needed.

Electronic supplementary material

The online version of this article (10.1186/s12906-018-2229-2) contains supplementary material, which is available to authorized users.

A New C-methyl Isoflavone and Other Compounds from the Roots of Amphiblemma monticola(Melastomataceae)

The phytochemical study of the EtOH extract of the roots of Amphiblemma monticola Jacq.-Fél. led to the isolation of a new C-methyl isoflavone, amphiblemmone A (1), along with ten known compounds, including 3,4’-di- O-methylellagic acid (2), dimethyl 4,4’,5,5’,6,6’- hexahydroxybiphenyl-2,2’-dicarboxylate (3), lupeol (4), ellagic acid (5), β-sitosterol (6), sitosterol 3- O-β-D-glucopyranoside (7), 3-hydroxy-4,5-dimethoxybenzoic acid (8), 3- O-methylellagic acid 4′- O-β-D-xylopyranoside (9), and a mixture of oleanolic acid (10) and ursolic acid (11). The structures were elucidated using spectroscopic analyses (IR, UV, NMR and MS) and comparison with literature data. Compounds 2-11 were isolated for the first time from the genus Amphiblemma. This is the first report of compounds 2-4, 8 and 9 from the Melastomataceae family.

Decorosides A and B, Cytotoxic Flavonoid Glycosides from the Leaves of Rhododendron decorum

Bioassay and NMR-guided fractionation of the methanolic extract of Rhododendron decorum leaves resulted in the isolation of two new flavonoid glycosides, 5,7-dihydroxy-6,8-dimethyldihydroflavanone-7-O-α-L-arabinopyranosyl(l→6)-β-D-glucopyranoside (decoroside A, 1) and its 3-hydroxy congener (decoroside B, 2), along with five known compounds myricitrin (3), afzelin (4), (-)-epicatechin (5), (+)-catechin (6), and ampeloptin (7). The structures of the isolated compounds were elucidated by extensive interpretation of their spectral data. Biological evaluation using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay revealed promising cytotoxic activities of these compounds against different cancer cell lines.

Flavanones from Miconia prasina

A glycosidic flavanone miconioside C (1) has been isolated from the methanolic extract of the stems of Miconia prasina, together with 7-O-β-D-apiofuranosyl-(1→6)-β-D-glucopyranosylmatteucinol (2), miconioside B (3), matteucinol (4), farrerol (5) and desmethoxymatteucinol (6). Their structures were mainly established by extensive NMR studies (¹H NMR, ¹³C NMR, DEPT, ¹H-¹H COSY, HSQC, HMBC) and mass spectrometry. The compounds 1- 3 were evaluated for in vitro binding assays using cannabinoid receptors (CB1 and CB2).

New Cycloartane-type Triterpenes from Marcetia Latifolia (Melastomataceae) and In Silico Studies on Candida Parapsilosis Protease

We have previously reported the antimicrobial activity of the ethyl acetate extract of Marcetia latifolia, particularly against Candida parapsilosis. In this work we describe the isolation of two new cycloartane-type triterpenes, 28,29- bis-norcycloartan-3β,4α-diol (1) and 28,29- bis-norcycloart-24-en-3β,4α-diol (2) from the same extract. These compounds were mainly characterized by one- (1H, 13C and APT) and two-dimensional (1H-1H-COSY, 1H-1H-NOESY, HMQC and HMBC) NMR spectroscopy, mass spectrometry and comparison with published structural data. In addition, the activity of triterpenes 1 and 2 on the Candida protease target was investigated by in silico methods using molecular docking.

Prenylated cinnamate and stilbenes from Kangaroo Island propolis and their antioxidant activity

A prenylated cinnamic acid derivative as well as six prenylated tetrahydroxystilbenes were isolated from the ethyl acetate extract of propolis that originated from Kangaroo Island, Australia. Furthermore, six known stilbenes and two known flavanones were also identified from the same sample. Stilbenes are not common in propolis; therefore, Kangaroo Island propolis is considered a unique type of propolis that is rich in prenylated stilbenes. Stilbene propolis from Kangaroo Island showed a stronger scavenging activity towards DPPH free radical than Brazilian green propolis. This strong activity can be explained by the presence of large number of stilbenes, most of them showed strong free radical scavenging activity.

Two flavonoid glycosides and a phenylpropanoid glucose ester from the leaves of Sterculia foetida

Two new flavonoid glycosides, hypolaetin 4'-methyl ether 8-O-beta-d-glucuronide 2''-sulfate (1) and hypolaetin 4'-methyl ether 3'-O-beta-d-glucoside (2), and a new phenylpropanoid glucose ester, 1,6-diferuloyl glucose (3), were isolated from the leaves of Sterculia foetida L. Their structures were elucidated by spectroscopic analysis and chemical evidence.

Naturally Occurring Flavanones: An Overview

Flavanones are one of the most interesting naturally occurring flavonoids in view of their structural pattern as well as biological and pharmacological potentials. The present review deals with natural flavanones reported from 1998 to mid 2007, along with their biological and pharmacological activities. The review includes more than 160 new naturally occurring flavanones from 135 references. The reported flavonoids belong to thirty-six plant families.

A simple route for renewable nano-sized arjunolic and asiatic acids and self-assembly of arjuna-bromolactone

While separating two natural nano-sized triterpenic acids via bromolactonization, we serendipitously discovered that arjuna-bromolactone is an excellent gelator of various organic solvents. A simple and efficient method for the separation of two triterpenic acids and the gelation ability and solid state 1D-helical self-assembly of nano-sized arjuna-bromolactone are reported.

Flavonoids from the Fern Chingia sakayensis (Zeiller) Holtt. and Evaluation of Their Cytotoxicity Against Murine Leukemia P-388 Cells

Three flavonoids, pinocembrin (1), farrerol (2) and matteucinol-7- O-α-L-arabinopyranosyl (1→6)-β-D-glucopyranoside (miconioside A) (3), were isolated for the first time from the fern Chingia sakayensis (Zeiller) Holtt (Thelypteridaceae). Their structures were elucidated from spectroscopic evidence and by comparison with reported literature data. All three isolated flavonoids showed only moderate activity against murine leukemia P-388 cells, with IC50 values greater than 100 μg/mL.