Chemical constituents of kino extract from Corymbia torelliana

The Ethnopharmacology, Phytochemistry and Bioactivities of the Corymbia Genus (Myrtaceae)

Plants have been vital to human survival for aeons, especially for their unique medicinal properties. Trees of the Eucalyptus genus are well known for their medicinal properties; however, little is known of the ethnopharmacology and bioactivities of their close relatives in the Corymbia genus. Given the current lack of widespread knowledge of the Corymbia genus, this review aims to provide the first summary of the ethnopharmacology, phytochemistry and bioactivities of this genus. The Scopus, Web of Science, PubMed and Google Scholar databases were searched to identify research articles on the biological activities, phytochemistry and ethnomedical uses of Corymbia species. Of the 115 Corymbia species known, 14 species were found to have ethnomedical uses for the leaves, kino and/or bark. Analysis of the references obtained for these 14 Corymbia spp. revealed that the essential oils, crude extracts and compounds isolated from these species possess an array of biological activities including anti-bacterial, anti-fungal, anti-protozoal, anti-viral, larvicidal, insecticidal, acaricidal, anti-inflammatory, anti-oxidant, anti-cancer and anti-diabetic activities, highlighting the potential for this under-studied genus to provide lead compounds and treatments for a host of medical conditions.

Flavonolignans and biflavonoids from Cephalotaxus oliveri exert neuroprotective effect via Nrf2/ARE pathway

Plants of the Cephalotaxus genus are rich in structurally diverse and naturally bioactive components, while limited studies have been reported for Cephalotaxus oliveri. Two undescribed flavonolignans and four undescribed biflavonoids, as well as thirteen known compounds, were isolated from the twigs and leaves of C. oliveri. Their structures were characterized by spectroscopic data analysis, and the absolute configurations were determined by electronic circular dichroism (ECD) calculations. All the isolated compounds were assayed for their neuroprotective activity against hydrogen peroxide (H2O2)-induced SH-SY5Y cell injury. All six undescribed compounds were effective to some degree, and umcephabiflovin B, apigenin 5-O-α-L-rhamnopyranosyl-(1 → 2)-6″-acetyl-β-D-glucopyranoside, and apigenin 7-O-β-D-glucoside exhibited good neuroprotective activity. Umcephabiflovin B protected SH-SY5Y cells against H2O2-induced neurotoxicity by repressing oxidative stress and apoptosis and by activating the nuclear factor erythroid 2-related factor 2 (Nrf2)/antioxidant-response element (ARE) pathway.

Naringenin and Its Derivatives-Health-Promoting Phytobiotic against Resistant Bacteria and Fungi in Humans

Naringenin is a trihydroxyflavanone present in large amount in different citrus fruits, e.g., oranges, pomelos, grapefruits, but also in tomatoes, fenugreek and coffee. It has a wide range of pharmacological and biological effects beneficial to human health. Its antioxidant, anti-cancer, anti-inflammatory, antifungal and antimicrobial activity is frequently reported in scientific literature. In this review we presented the current state of knowledge on the antimicrobial activity of naringenin and its natural and synthetic derivatives as a phytobiotic against resistant Gram-positive and Gram-negative bacteria as well as fungi in humans. Most of the data reported here have been obtained from in vitro or in vivo studies. Over the past few years, due to the overuse of antibiotics, the occurrence of bacteria resistant to all available antibiotics has been growing. Therefore, the main focus here is on antibiotic resistant strains, which are a significant, worldwide problem in the treatment of infectious diseases. The situation is so alarming that the WHO has listed microbial resistance to drugs on the list of the 10 most important health problems facing humanity. In addition, based on scientific reports from recent years, we described the potential molecular mechanism of action of these bioflavonoids against pathogenic strains of microorganisms. As plant-derived substances have been pushed out of use with the beginning of the antibiotic era, we hope that this review will contribute to their return as alternative methods of preventing and treating infections in the epoch of drug resistance.

Entomopathogenic Filamentous Fungi as Biocatalysts in Glycosylation of Methylflavonoids

Flavonoids are known for their numerous biological activities; however, their pharmacological application is limited by poor bioavailability. Glycosides are usually more stable and more soluble in water and in this form, flavonoids are present in nature. Likewise, the presence of the methyl group in the flavonoid skeleton results in facilitated absorption and greater bioavailability. Entomopathogenic filamentous fungi are effective in the biotransformation of flavonoids; they are known especially for efficient glycosylation. In the current study we used strains of Beauveria bassiana KCH J1.5 and Isaria fumosorosea KCH J2 to biotransform flavonoids with a single methyl group. 2′-Hydroxy-5′-methylchalcone was biotransformed by both strains into 2′-hydroxy-5′-methylchalcone 3-O-β-D-(4″-O-methyl)-glucopyranoside. In the culture of B. bassiana KCH J1.5 four products were obtained from 6-methylflavanone: 4′-hydroxy-6-methylflavanone 3′-O-β-D-(4″-O-methyl)-glucopyranoside; 4′-hydroxyflavanone 6-methylene-O-β-D-(4″-O-methyl)-glucopyranoside; 6-hydroxymethylflavanone 3′-O-β-D-(4″-O-methyl)-glucopyranoside and 4′-hydroxy-6-hydroxymethylflavanone 3′-O-β-D-(4″-O-methyl)-glucopyranoside. Biotransformation with I. fumosorosea KCH J2 as a biocatalyst resulted in the formation of 6-methylflavanone 4′-O-β-D-(4″-O-methyl)-glucopyranoside and 2-phenyl-6-methylchromane 4-O-β-D-(4″-O-methyl)-glucopyranoside. All of these flavonoids can be used in biological activity tests and can be useful in studies concerning structure—bioactivity relationships.

Diterpenoids and Flavonoids from the Twigs of Cephalotaxus fortunei var. alpina

Three new diterpenoids (a cephalotane, an abietane and a 9(10→20)-abeo-abietane) and one new flavonoid, together with 11 known compounds, were isolated from the twigs of Cephalotaxus fortunei var. alpina. The new compounds were identified by comprehensive spectroscopic (including 1D and 2D-NMR and HR-ESI-MS) analysis. Anti-inflammatory, immunosuppressive and cytotoxic activities of three new compounds were evaluated. 3β,20-epoxyabieta-8,11,13-triene-3α,12-diol showed weak cytotoxicity against tumor cell lines NCI-H1975, HepG2, MCF-7, while fortalpinoid R and 3-acetonyl-3,5,7,4'-tetrahydroxy-2-methoxyflavanone were not active at 80 μM. None of these compounds showed anti-inflammatory and immunosuppressive activities.

Chemical constituents and acetylcholinesterase inhibitory activity from the stems of Bauhinia pentandra

Two steroids (1 and 2), two oxepin derivatives (3 and 4) and seven flavonoids (5-11) were isolated from the stems of Bauhinia pentandra. Their structures were elucidated on the basis of NMR spectroscopic data, and by comparison with data previously reported in the literature. The ethanol extract from the stems of B. pentandra and the compounds, 4, 5, 6, 7, 8 and 11 have been evaluated as acetylcholinesterase inhibitors, and among these, the compound 5 exhibited the strongest activity. In addition, all the isolated compounds are reported for the first time as constituents of B. pentandra.

Occurrence and distribution of unsubstituted B-ring flavanones in Eucalyptus foliage

A group of plant specialised metabolites (PSMs) collectively known as unsubstituted B-ring flavanones (UBFs) have previously been found in the foliage of some species from the genus Eucalyptus L'Hér. (Myrtaceae), specifically from the subgenus Eucalyptus (monocalypts). Captive feeding studies using artificial diets suggest that these compounds may potentially influence the feeding preferences of marsupial folivores, such as koalas. Understanding natural variation in the composition and concentration of UBFs in eucalypt foliage is a first step to deciding whether, through their effects on herbivory, they might have broader effects on ecosystem dynamics. We used ESI-LCMS/MS and HPLC to characterise and quantify UBFs in 351 individual trees from 25 monocalypt species. We found large variation in the total UBF concentration both between and within species. For example, the mean concentration of UBFs in Eucalyptus muelleriana was 0.2 mg g^-1 dry wt, whereas it was 105.7 mg g^-1 dry wt, with a range of 78.2-141.3 mg g^-1 dry wt, in Eucalyptus mediocris. Different eucalypt species contained different subsets of ten UBFs, and three species showed potential chemotypic variation between individuals within species. Our results suggest that UBFs naturally vary between monocalypt species and individuals at concentrations that could realistically be expected to affect the feeding dynamics of marsupial eucalypt folivores. UBFs could be measured relatively rapidly and cheaply in future studies using near-infrared reflectance (NIR) spectroscopy, as we were able to successfully predict the total UBF concentration of samples from their NIR spectra, with an r² value of 0.98 and a standard error of prediction (SEP) of 6.07. This work further solidifies NIR spectroscopy as a powerful tool enabling ecologists to analyse the chemical composition of large numbers of samples.

Novel O-alkyl Derivatives of Naringenin and Their Oximes with Antimicrobial and Anticancer Activity

In our investigation, we concentrated on naringenin (NG)—a widely studied flavanone that occurs in citrus fruits. As a result of a reaction with a range of alkyl iodides, 7 novel O-alkyl derivatives of naringenin (7a–11a, 13a, 17a) were obtained. Another chemical modification led to 9 oximes of O-alkyl naringenin derivatives (7b–13b, 16b–17b) that were never described before. The obtained compounds were evaluated for their potential antibacterial activity against Escherichia coli, Staphylococcus aureus, and Bacillus subtilis. The results were reported as the standard minimal inhibitory concentration (MIC) values and compared with naringenin and its known O-alkyl derivatives. Compounds 4a, 10a, 12a, 14a, 4b, 10b, 11b, and 14b were described with MIC of 25 µg/mL or lower. The strongest bacteriostatic activity was observed for 7-O-butylnaringenin (12a) against S. aureus (MIC = 6.25 µg/mL). Moreover, the antitumor effect of flavonoids was examined on human colon cancer cell line HT-29. Twenty-six compounds were characterized as possessing an antiproliferative activity stronger than that of naringenin. The replacement of the carbonyl group with an oxime moiety significantly increased the anticancer properties. The IC₅₀ values below 5 µg/mL were demonstrated for four oxime derivatives (8b, 11b, 13b and 16b).

Antiplasmodial β-Triketone-Flavanone Hybrids from the Flowers of the Australian Tree Corymbia torelliana

The methanol extract of the flowers of the Australian eucalypt tree Corymbia torelliana yielded six new β-triketone-flavanone hybrids, torellianones A-F (1-6), the tetrahydroxycyclohexane torellianol A (7), and known β-triketones (4 S)-ficifolidione (8) and (4 R)-ficifolidione (9), and β-triketone-flavanones kunzeanone A (10) and kunzeanone B (11). Torellianones A and B, C and D, and E and F were each isolated as inseparable diastereomeric mixtures. Exchange correlations observed in a ROESY spectrum indicated that 5 and 6 also interconverted between stable conformers. The structures of 1-7 were elucidated from the analysis of 1D/2D NMR and MS data. Relative configurations of torellianones C-F and torrellianol A were determined from analysis of ROESY data. Compounds 1-10 were tested for antiplasmodial activity against a drug-sensitive (3D7) strain of Plasmodium falciparum, with 3-6 and 8-10 showing limited antiplasmodial activity, with IC₅₀ values ranging from 3.2 to 16.6 μM.

Antibacterial Properties of Flavonoids from Kino of the Eucalypt Tree, Corymbia torelliana

Traditional medicine and ecological cues can both help to reveal bioactive natural compounds. Indigenous Australians have long used kino from trunks of the eucalypt tree, Corymbia citriodora, in traditional medicine. A closely related eucalypt, C. torelliana, produces a fruit resin with antimicrobial properties that is highly attractive to stingless bees. We tested the antimicrobial activity of extracts from kino of C. citriodora, C. torelliana × C. citriodora, and C. torelliana against three Gram-negative and two Gram-positive bacteria and the unicellular fungus, Candida albicans. All extracts were active against all microbes, with the highest activity observed against P. aeruginosa. We tested the activity of seven flavonoids from the kino of C. torelliana against P. aeruginosa and S. aureus. All flavonoids were active against P. aeruginosa, and one compound, (+)-(2S)-4',5,7-trihydroxy-6-methylflavanone, was active against S. aureus. Another compound, 4',5,7-trihydroxy-6,8-dimethylflavanone, greatly increased biofilm formation by both P. aeruginosa and S. aureus. The presence or absence of methyl groups at positions 6 and 8 in the flavonoid A ring determined their anti-Staphylococcus and biofilm-stimulating activity. One of the most abundant and active compounds, 3,4',5,7-tetrahydroxyflavanone, was tested further against P. aeruginosa and was found to be bacteriostatic at its minimum inhibitory concentration of 200 µg/mL. This flavanonol reduced adhesion of P. aeruginosa cells while inducing no cytotoxic effects in Vero cells. This study demonstrated the antimicrobial properties of flavonoids in eucalypt kino and highlighted that traditional medicinal knowledge and ecological cues can reveal valuable natural compounds.

Synthesis and Biological Activity of Novel O-Alkyl Derivatives of Naringenin and Their Oximes

O -Alkyl derivatives of naringenin ( 1a - 10a ) were prepared from naringenin using the corresponding alkyl iodides and anhydrous potassium carbonate. The resulting products were used to obtain oximes ( 1b - 10b ). All compounds were tested for antimicrobial activity against Escherichia coli ATCC10536, Staphylococcus aureus DSM799, Candida albicans DSM1386, Alternaria alternata CBS1526, Fusarium linii KB-F1, and Aspergillus niger DSM1957. The resulting biological activity was expressed as the increase in optical density (ΔOD). The highest inhibitory effect against E. coli ATCC10536 was observed for 7,4'-di- O -pentylnaringenin ( 8a ), 7- O -dodecylnaringenin ( 9a ), naringenin oxime ( NG-OX ), 7,4'-di- O -pentylnaringenin oxime ( 8b ), and 7- O -dodecylnaringenin oxime ( 9b ) (ΔOD = 0). 7- O -dodecylnaringenin oxime ( 9b ) also inhibited the growth of S. aureus DSM799 (ΔOD = 0.35) and C. albicans DSM1386 (ΔOD = 0.22). The growth of A. alternata CBS1526 was inhibited as a result of the action of 7,4'-di- O -methylnaringenin ( 2a ), 7- O -ethylnaringenin ( 4a ), 7,4'-di- O -ethylnaringenin ( 5a ), 5,7,4'-tri- O -ethylnaringenin ( 6a ), 7,4'-di- O -pentylnaringenin ( 8a ), and 7- O -dodecylnaringenin ( 9a ) (ΔOD in the range of 0.49-0.42) in comparison to that of the control culture (ΔOD = 1.87). In the case of F. linii KB-F1, naringenin ( NG ), 7,4'-di- O -dodecylnaringenin ( 10a ), 7- O -dodecylnaringenin oxime ( 9b ), and 7,4'-di- O -dodecylnaringenin oxime ( 10b ) showed the strongest effect (ΔOD = 0). 7,4'-Di- O -pentylnaringenin ( 8a ) and naringenin oxime ( NG-OX ) hindered the growth of A. niger DSM1957 (ΔOD = 0).

Anti-inflammatory activities of compounds from twigs of Morus alba

Five new compounds, 10-oxomornigrol F (1), (7″R)-(-)-6-(7″-hydroxy-3″,8″-dimethyl-2″,8″-octadien-1″-yl)apigenin (2), ramumorin A (3), ramumorin B (4), and (4S,7S,8R)-trihydroxyoctadeca-5Z-enoic acid (5), together with 31 known compounds (6-36), were isolated from the twigs of Morus alba (Moraceae). The chemical structures of these compounds were established using spectroscopic analyses, 1D and 2D NMR, high-resolution electrospray ionization mass spectrometry (HRESIMS), and Mosher's methods. The anti-inflammatory activities of the compounds were evaluated by investigating their ability to inhibit lipopolysaccharide (LPS)-induced nitric oxide (NO) production in macrophage RAW 264.7 cells. Compounds 1, 2, 13, 17, 19, 25-28, and 32 showed inhibitory effects with IC₅₀ values ranging from 2.2 to 5.3μg/mL. Compounds 1, 2, 17, 25, and 32 reduced LPS-induced inducible nitric oxide synthase (iNOS) expression in a concentration-dependent manner. In addition, pretreating the cells with compound 1, 17, and 32 significantly suppressed LPS-induced expression of cyclooxygenase-2 (COX-2) protein.

Do Hybrid Trees Inherit Invasive Characteristics? Fruits of Corymbia torelliana X C. citriodora Hybrids and Potential for Seed Dispersal by Bees

Tree invasions have substantial impacts on biodiversity and ecosystem functioning, and trees that are dispersed by animals are more likely to become invasive. In addition, hybridisation between plants is well documented as a source of new weeds, as hybrids gain new characteristics that allow them to become invasive. Corymbia torelliana is an invasive tree with an unusual animal dispersal mechanism: seed dispersal by stingless bees, that hybridizes readily with other species. We examined hybrids between C. torelliana and C. citriodora subsp. citriodora to determine whether hybrids have inherited the seed dispersal characteristics of C. torelliana that allow bee dispersal. Some hybrid fruits displayed the characteristic hollowness, resin production and resin chemistry associated with seed dispersal by bees. However, we did not observe bees foraging on any hybrid fruits until they had been damaged. We conclude that C. torelliana and C. citriodora subsp. citriodora hybrids can inherit some fruit characters that are associated with dispersal by bees, but we did not find a hybrid with the complete set of characters that would enable bee dispersal. However, around 20,000 hybrids have been planted in Australia, and ongoing monitoring is necessary to identify any hybrids that may become invasive.

Antimicrobial and antioxidant activities and phenolic profile of Eucalyptus globulus Labill. and Corymbia ficifolia (F. Muell.) K.D. Hill & L.A.S. Johnson leaves

This study was performed to evaluate the in vitro antimicrobial and antioxidant activities and the phenolic profile of Eucalytus globulus Labill. and Corymbia ficifolia (F. Muell.) K.D. Hill & L.A.S. Johnson leaves. Both leave extracts contain significant amounts of phenolic compounds, mainly flavonoids. Qualitative and quantitative analyses of the phenolic compounds were performed using a HPLC/MS method. The main flavonoid was hyperoside and its highest amount was found in E. globulus (666.42 ± 5.02 μg/g dw plant material). Regarding the flavonol profile, myricetin was the dominant compound and its highest amount was found in C. ficifolia leaves (124.46 ± 0.24 μg/g dw plant material). The antioxidant activity was evaluated by DPPH, TEAC, hemoglobin ascorbate peroxidase activity inhibition (HAPX) and inhibition of lipid peroxidation catalyzed by cytochrome c assays, revealing an important antioxidant potential for both species. In the antimicrobial assays, C. ficifolia extract was found to be more active than E. globulus against both Gram-positive and Gram-negative bacterial strains with the exception of Bacillus subtilis. The results of the present study provide new valuable data regarding the bioactivities of these medicinal species.