In vitro antimycobacterial studies of flavonols from Bauhinia vahlii Wight and Arn

Anti-Neuroinflammatory Effect of Ombuin from Rhamnus erythroxylon Pall. Leaves in LPS-Induced BV-2 Microglia by Targeting Src and Suppressing the PI3K-AKT/NF-κB Signaling Pathway

The leaves of Rhamnus erythroxylon Pall. are widely used as tea substitutes in northwest China for their fragrant aroma, anti-irritability, and digestion-enhancing properties. Ombuin, a main flavonoid compound found in the leaves, exhibited notable anti-inflammatory and antioxidant effects. However, its potential role in treating neuroinflammatory-related diseases remains unexplored. Thus, this study aims to evaluate the anti-neuroinflammatory effects of ombuin and to explore the underlying molecular mechanisms. According to our findings, ombuin dramatically reduced the release of interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), IL-1β, nitric oxide (NO), and reactive oxygen species (ROS) in lipopolysaccharide (LPS)-stimulated BV-2 microglia. Further analysis, including transcriptomics, network pharmacology, molecular docking, and cellular heat transfer assays, revealed that Src was a direct target of ombuin. Western blot analysis showed that ombuin effectively suppressed Src phosphorylation and inhibited the downstream expressions of p-PI3K p85, p-AKT1, p-IKKα/β, p-IκBα, and nuclear factor κB (NF-κB). Meanwhile, the repression of Src significantly reversed the anti-neuroinflammatory activity of ombuin. Our results identified Src as a direct target of ombuin and implied that ombuin exerted an anti-neuroinflammatory effect by inhibiting Src phosphorylation and suppressing the activation of the PI3K-AKT and NF-κB pathways, which might provide an alternative therapeutic strategy for neurodegenerative diseases.

Physical characteristics of quercetin pulmospheres using combination of alginate-carrageenan: Effect of polymer concentration

Indonesia is the second country with the highest number of tuberculosis (TB) cases in the world and the first in Southeast Asia, according to WHO Global Report 2020. Quercetin has been tried as an alternative therapy and was found effective. This study aims to optimize quercetin pulmospheres using combination polymers and study its characteristics as an inhalation delivery system. Combination polymers provide the advantages of safe, mucoadhesive, and compact pulmospheres. Pulmospheres were made as formula F1, F2, and F3 (polymer ratios of 1:1, 1:2, and 1:3), respectively. Pulmospheres were made with quercetin 0.2%, alginate-carrageenan (total concentration of 1.8%), and CaCl2 0.5 M. Characterization of particle size, morphology, moisture content (MC), yield, drug loading, and entrapment efficiency (EE) were conducted. The yield range was from 83.89 to 86.30% ± 4.59%. MC range was from 4.23 to 5.12% ± 0.05%. Particle size was <3 µm (between 2.19 and 2.76 ± 0.149 µm), spherical shape and smooth surface. EE range was 60.69% ± 4.45% to 77.86% ± 1.74% and the drug loading range was 1.66-2.09% ± 0.15%. F2 formula with a polymer ratio of 1:2 was the best quercetin pulmospheres. Potential pulmospheres will then be recommended for in vitro release and in vivo study.

From nature's bounty to drug discovery: Leveraging phytochemicals and molecular approaches to combat multi-drug-resistant (MDR) tuberculosis

A large number of people annually lose their lives to tuberculosis (TB), which is an age-old disease caused by the Mycobacterium tuberculosis. The global spread of TB is a concern for all regions. The south-east Asian region recorded 46% of all new TB cases in 2021, followed by the African and western Pacific regions with 23% and 18%, respectively. Researchers are always searching at natural substances for potential alternative therapeutics to tackle the worrisome growth in multi-drug-resistant (MDR) tuberculosis due to the high costs associated with developing new treatments and unfavourable side effects of currently used synthetic pharmaceuticals. Phytochemicals show promising results as a future health aid due to their multi-targeting ability on pathogen cells. In the search for new drug leads, the Ayurvedic and Siddha medical systems have made an extensive use of ethnomedicinal tools, including the use of plants like Amalaki (Emblica officinalis Gaertn.), Guduchi (Tinospora cordifolia willd.), Sariva (Hemidesmus indicus R.Br.), Kustha (Saussurea lappa Falc.), turmeric (Curcuma longa Mal.) and Green tea (Camellia sinensis Linn.). These sources are high in flavonoids, polyphenols, tannins and catechins, has been shown to reduce the risk of TB. In this overview, we look at how natural sources like plants, algae and mushrooms have helped researchers to find new drug leads, and how to back these natural sources through mapping the molecular approaches and other approaches has helped them to defeat MDR.

Kaempferol: Antimicrobial Properties, Sources, Clinical, and Traditional Applications

Flavonoids are a category of plant-derived compounds which exhibit a large number of health-related effects. One of the most well-known and studied flavonoids is kaempferol, which can be found in a wide variety of herbs and plant families. Apart from their anticarcinogenic and anti-inflammatory effects, kaempferol and its associated compounds also exhibit antibacterial, antifungal, and antiprotozoal activities. The development of drugs and treatment schemes based on these compounds is becoming increasingly important in the face of emerging resistance of numerous pathogens as well as complex molecular interactions between various drug therapies. In addition, many of the kaempferol-containing plants are used in traditional systems all over the world for centuries to treat numerous conditions. Due to its variety of sources and associated compounds, some molecular mechanisms of kaempferol antimicrobial activity are well known while others are still under analysis. This paper thoroughly documents the vegetal and food sources of kaempferol as well as the most recent and significant studies regarding its antimicrobial applications.

Overexpression of RuFLS2 Enhances Flavonol-Related Substance Contents and Gene Expression Levels

As an emerging third-generation fruit, blackberry has high nutritional value and is rich in polyphenols, flavonoids and anthocyanins. Flavonoid biosynthesis and metabolism is a popular research topic, but no related details have been reported for blackberry. Based on previous transcriptome data from this research group, two blackberry flavonol synthase genes were identified in this study, and the encoded proteins were subjected to bioinformatics analysis. RuFLS1 and RuFLS2 are both hydrophobic acidic proteins belonging to the 2OG-Fe(II) dioxygenase superfamily. RuFLS2 was expressed at 27.93-fold higher levels than RuFLS1 in red-purple fruit by RNA-seq analysis. Therefore, RuFLS2-overexpressing tobacco was selected for functional exploration. The identification of metabolites from transgenic tobacco showed significantly increased contents of flavonoids, such as apigenin 7-glucoside, kaempferol 3-O-rutinoside, astragalin, and quercitrin. The high expression of RuFLS2 also upregulated the expression levels of NtF3H and NtFLS in transgenic tobacco. The results indicate that RuFLS2 is an important functional gene regulating flavonoid biosynthesis and provides an important reference for revealing the molecular mechanism of flavonoid accumulation in blackberry fruit.

Ombuin ameliorates diabetic nephropathy in rats by anti-inflammation and antifibrosis involving Notch 1 and PPAR γ signaling pathways

Diabetic nephropathy (DN) is a common complication of diabetes and it is urgent to develop effective therapies for DN. In this study, high-sucrose and high-fat diet combined with streptozotocin was used to induce DN in rats to observe the effects of natural flavonoid ombuin on renal function, inflammation, and interstitial fibrosis. Immunohistochemistry and western blotting analysis were used to detect protein expression levels. Results showed that ombuin significantly improved renal function and pathological injury, inhibited accumulation of advanced glycation end-products, suppressed the release of inflammatory cytokines, and improved renal interstitial fibrosis in DN rats. Ombuin also significantly downregulated the expressions of transforming growth factor beta1 (TGF-β1), connective tissue growth factor (CTGF), fibronectin (FN), p65, phosphorylated (p)-p65, Cleaved-Notch 1, and hairy and enhancer of split 1 (Hes 1), and upregulated the expression of peroxisome proliferator-activated receptor γ (PPAR γ). When PPAR γ activity was inhibited by T0070907, the effects of ombuin on improving DN were significantly reversed, and the expressions of TGF-β1, FN, CTGF, p-p65, and p65 increased, while the expressions of Cleaved-Notch 1 and Hes 1 were not significantly affected. These results suggest that ombuin may activate PPAR γ to exert anti-inflammatory and antifibrotic effects by inhibiting Notch 1 activity in DN. It is also possible that ombuin acts on these two independent signal pathways synchronously.

Bioassay-guided isolation of antimycobacterial substances from the traditionally used lichen Cladonia pyxidata (L.) Hoffm

The aim of the present study is to provide a scientific rationale for the folklore usage of Cladonia pyxidata (L.) Hoffm. in treating tuberculosis (Tb). Through bioassay-guided isolation, antimycobacterial metabolites were isolated from under-investigated lichen C. pyxidata and examined against M.t H37Ra and six MDR strains. Further, the cytotoxicity of all isolated metabolites was evaluated on THP-1 macrophages. Bioassay-guided isolation of acetone extract of C. pyxidata yielded four metabolites, namely usnic acid, atranorin, barbatic acid, and fumarprotocetraric acid. Among those, the MIC values of usnic acid and fumarprotocetraric acid showed more effective in inhibiting the growth of six MDR strains, compared to first-line drug rifampicin. In addition, the 50% inhibitory concentration values of these two compounds on THP-1 were found to be far higher than MIC values against tested Tb strains, indicating that THP-1 macrophages were not harmfully affected at concentrations that were effective against M.t and MDR strains. The results exposed the traditional use of C. pyxidata for treating Tb, and the key metabolites were found to be usnic acid and fumarprotocetraric acid. The current study lends the first evidence for the presence of antimycobacterial compounds in C. pyxidata.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-022-03159-6.

Antimycobacterial activity of acetone extract and isolated metabolites from folklore medicinal lichen Usnea laevis Nyl. against drug-sensitive and multidrug-resistant tuberculosis strains

ETHNOPHARMACOLOGICAL RELEVANCE

Tuberculosis (Tb) is one of the most infectious diseases caused by Mycobacterium tuberculosis (M.t) with almost 2 million deaths yearly. Although many Tb control programs have been organised, there is an elevated number of Tb cases due to the appearance of extremely drug-resistant and multidrug-resistant (MDR) Tb strains. In the cultures of Venezuelan Andes, fruticose lichen Usnea laevis Nyl. (Usneaceae) with folklore name 'Barba de Piedra, Tusinya' is used as a natural remedy for Tb.

AIM OF THE STUDY

This study was performed to provide a scientific rationale for the folklore usage of U. laevis in treating Tb by validating its antimycobacterial activity against two drug-sensitive and four MDR-Tb strains.

MATERIALS AND METHODS

The mycobacterial inhibitory activities of acetone extract (Ul), fractions (F1-10), and isolated metabolites (1-4) of U. laevis were evaluated against M.t H37Ra using 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide reduction menadione assay (XRMA). Furthermore, Ul and 1-4 were subjected to antimycobacterial activity against M.t H37Ra, Mycobacterium smegmatis, and four MDR-Tb (MDR-A8, MDR-V791, MDR-R and MDR-40) strains using resazurin microtitre plate assay (REMA) and cytotoxicity against THP-1 macrophages using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and their selectivity index values were also calculated.

RESULTS

Initially, Ul has shown prominent inhibitory activity (IC₅₀ value: 5.44 ± 0.36 μg/ml) and four of its fractions (F1, F2, F5 and F7) also exhibited the best inhibitory activity (IC₅₀ values ranged from 7.46 ± 0.19 to 71.38 ± 2.57 μg/ml) against M.t H37Ra using XRMA. Purification of these bioactive fractions identified four metabolites, namely usnic acid (1), atranorin (2), salazinic acid (3), and lobaric acid (4). From the MIC values of REMA, it was identified that Ul, 1 and 4 were more effective in inhibiting the growth of all four MDR-Tb strains, compared to first-line drug rifampicin. Interestingly, Ul has shown better antimycobacterial activity than 1-4 and rifampicin against MDR-Tb strains may be due to the synergistic effect of its metabolites. Also, the IC₅₀ values of Ul and 1-4 on THP-1 macrophages were found to be far higher than MIC values against tested Tb strains, indicating that THP-1 macrophages were not harmfully affected at concentrations that were effective against Tb strains. Further, the calculated selectivity index values revealed the more active and non-toxicity of Ul, 1 and 4 against MDR-Tb strains than rifampicin.

CONCLUSIONS

The current study lends the first evidence for the presence of antimycobacterial metabolites in U. laevis. The results exposed the Andean folklore use of U. laevis for treating Tb, and the key biomarker metabolites were found to be 1 and 4. Hence, it can be concluded that U. laevis can be used as a potential source for the novel drug development for MDR-Tb.