Interactions of a prenylated flavonoid from Dalea elegans with fluconazole against azole- resistant Candida albicans

Prenylated Flavanone Isolated from Dalea Species as a Potential Multitarget-Neuroprotector in an In Vitro Alzheimer's Disease Mice Model

Alzheimer's disease (AD) involves a neurodegenerative process that has not yet been prevented, reversed, or stopped. Continuing with the search for natural pharmacological treatments, flavonoids are a family of compounds with proven neuroprotective effects and multi-targeting behavior. The American genus Dalea L. (Fabaceae) is an important source of bioactive flavonoids. In this opportunity, we tested the neuroprotective potential of three prenylated flavanones isolated from Dalea species in a new in vitro pre-clinical AD model previously developed by us. Our approach consisted in exposing neural cells to conditioned media (3xTg-AD ACM) from neurotoxic astrocytes derived from hippocampi and cortices of old 3xTg-AD mice, mimicking a local neurodegenerative microenvironment. Flavanone 1 and 3 showed a neuroprotective effect against 3xTg-AD ACM, being 1 more active than 3. The structural requirements to afford neuroprotective activity in this model are a 5'-dimethylallyl and 4'-hydroxy at the B ring. In order to search the mechanistic performance of the most active flavanone, we focus on the flavonoid-mediated regulation of GSK-3β-mediated tau phosphorylation previously reported. Flavanone 1 treatment decreased the rise of hyperphosphorylated tau protein neuronal levels induced after 3xTg-AD ACM exposure and inhibited the activity of GSK-3β. Finally, direct exposure of these neurotoxic 3xTg-AD astrocytes to flavanone 1 resulted in toxicity to these cells and reduced the neurotoxicity of 3xTg-AD ACM as well. Our results allow us to present compound 1 as a natural prenylated flavanone that could be used as a precursor to development and design of future drug therapies for AD.

Integrative Analysis of Metabolome and Transcriptome Identifies Potential Genes Involved in the Flavonoid Biosynthesis in Entada phaseoloides Stem

Entada phaseoloides stem is known for its high medicinal benefits and ornamental value. Flavonoids are one of the main active constituents in E. phaseoloides stem. However, the regulatory mechanism of flavonoids accumulation in E. phaseoloides is lacking. Here, phytochemical compounds and transcripts from stems at different developmental stages in E. phaseoloides were investigated by metabolome and transcriptome analysis. The metabolite profiling of the oldest stem was obviously different from young and older stem tissues. A total of 198 flavonoids were detected, and flavones, flavonols, anthocyanins, isoflavones, and flavanones were the main subclasses. The metabolome data showed that the content of acacetin was significantly higher in the young stem and older stem than the oldest stem. Rutin and myricitrin showed significantly higher levels in the oldest stem. A total of 143 MYBs and 143 bHLHs were identified and classified in the RNA-seq data. Meanwhile, 34 flavonoid biosynthesis structural genes were identified. Based on the expression pattern of structural genes involved in flavonoid biosynthesis, it indicated that flavonol, anthocyanin, and proanthocyanin biosynthesis were first active during the development of E. phaseoloides stem, and the anthocyanin or proanthocyanin biosynthesis branch was dominant; the flavone biosynthesis branch was active at the late developmental stage of the stem. Through the correlation analysis of transcriptome and metabolome data, the potential candidate genes related to regulating flavonoid synthesis and transport were identified. Among them, the MYBs, bHLH, and TTG1 are coregulated biosynthesis of flavonols and structural genes, bHLH and transporter genes are coregulated biosynthesis of anthocyanins. In addition, the WDR gene TTG1-like (AN11) may regulate dihydrochalcones and flavonol biosynthesis in specific combinations with IIIb bHLH and R2R3-MYB proteins. Furthermore, the transport gene protein TRANSPARENT TESTA 12-like gene is positively regulated the accumulation of rutin, and the homolog of ABC transporter B family member gene is positively correlated with the content of flavone acacetin. This study offered candidate genes involved in flavonoid biosynthesis, information of flavonoid composition and characteristics of flavonoids accumulation, improved our understanding of the MYBs and bHLHs-related regulation networks of flavonoid biosynthesis in E. phaseoloides stem, and provided references for the metabolic engineering of flavonoid biosynthesis in E. phaseoloides stem.

A state-of-the-art review and prospective therapeutic applications of prenyl flavonoids as chemosensitizers against antifungal multidrug resistance in Candida albicans

Multidrug resistance (MDR) in the opportunistic pathogen Candida albicans is defined as non-susceptibility to at least one agent in two or more drug classes. This phenomenon has been increasingly reported since the rise in the incidence of fungal infections in immunocompromised patients at the end of the last century. After the discovery of efflux pump overexpression as a principal mechanism causing MDR in Candida strains, drug discovery targeting fungal efflux transporters has had a growing impact. Chemosensitization aims to enhance azole intracellular concentrations through combination therapy with transporter inhibitors. Consequently, the use of drug efflux inhibitors combined with the antifungal agent will sensitize the pathogen. As a result, the use of lower drug concentrations will reduce possible adverse effects on the host. Through an extensive revision of the literature, this review aims to provide an exhaustive and critical analysis of the studies carried out in the past two decades, regarding the chemosensitization strategy to cope with multidrug resistance in C. albicans. This work provides a deep analysis of the research about the inhibition of drug-efflux membrane transporters by prenylated flavonoids and the interactions of these phytocompounds with azole antifungals as an approach to chemosensitize multidrug-resistant C. albicans strains. We highlight the importance of prenylflavonoids and their particular chemical and pharmacological characteristics that make them excellent candidates with therapeutic potential as chemosensitizers. Finally, we propose the need for further research of prenyl flavonoids as inhibitors of drug-efflux mediated fungal resistance.

RNA-Seq reveals the key pathways and genes involved in the light-regulated flavonoids biosynthesis in mango (Mangifera indica L.) peel

INTRODUCTION

Flavonoids are important water soluble secondary metabolites in plants, and light is one of the most essential environmental factors regulating flavonoids biosynthesis. In the previous study, we found bagging treatment significantly inhibited the accumulation of flavonols and anthocyanins but promoted the proanthocyanidins accumulation in the fruit peel of mango (Mangifera indica L.) cultivar 'Sensation', while the relevant molecular mechanism is still unknown.

METHODS

In this study, RNA-seq was conducted to identify the key pathways and genes involved in the light-regulated flavonoids biosynthesis in mango peel.

RESULTS

By weighted gene co-expression network analysis (WGCNA), 16 flavonoids biosynthetic genes were crucial for different flavonoids compositions biosynthesis under bagging treatment in mango. The higher expression level of LAR (mango026327) in bagged samples might be the reason why light inhibits proanthocyanidins accumulation in mango peel. The reported MYB positively regulating anthocyanins biosynthesis in mango, MiMYB1, has also been identified by WGCNA in this study. Apart from MYB and bHLH, ERF, WRKY and bZIP were the three most important transcription factors (TFs) involved in the light-regulated flavonoids biosynthesis in mango, with both activators and repressors. Surprisingly, two HY5 transcripts, which are usually induced by light, showed higher expression level in bagged samples.

DISCUSSION

Our results provide new insights of the regulatory effect of light on the flavonoids biosynthesis in mango fruit peel.

Conservation and diversification of flavonoid metabolism in the plant kingdom

Flavonoids are by far the largest class of polyphenols with huge structural and functional diversity. However, the mystery regarding the exact evolutionary pressures which lead to the amazing diversity in plant flavonoids has yet to be completely uncovered. Here we review recent advances in understanding the conservation and diversification of flavonoid pathway from algae and early land plants to vascular plants including the model plant Arabidopsis and economically important species such as cereals, legumes, and medicinal plants. Studies on the origin and evolution of R2R3-MYB regulatory system demonstrated its highly conserved function of regulating flavonoid production in land plants and this innovation appears to have been crucial in boosting the overall levels of these compounds in land plants. Convergent evolution has occurred as different flavonoids independently which emerged in distant taxa resulting in similar defense and tolerance characteristics against environmental stresses. Future studies on an increasing number of plant species taking advantage of newly developed genomic and metabolite profiling technologies are envisaged to provide comprehensive insight into flavonoid biosynthesis as well as pathway diversification and the underlying evolutionary mechanisms.

[Inhibitory effect of diethylstilbestrol on clinical strains of Candida albicans susceptible and resistant to azoles]

BACKGROUND

Candida albicans is a microorganism frequently involved in several infections; the patient's oral cavity, caries niches or periodontal disease can sometimes be the reservoir.. The fungal resistance to the available treatments, among other reasons, has led to the search for new antifungal alternatives.

AIMS

To carry out a comparative study of the in vitro effects of diethylstilboestrol (DES) and fluconazole (FLZ) on the growth of clinical strains of C. albicans.

METHODS

Seven strains of C. albicans were used: a) one FLZ-sensitive culture collection strain, ATCC 90028 (ATCC); b) four oral isolates from four oncological patients with periodontal disease (period 8, 9, 10, and 11); and c) two oral isolates from an AIDS patient with oropharyngeal candidiasis: one FLZ- sensitive (2-76), and another FLZ- resistant (12-99). The MIC was evaluated by standard spectrophotometric techniques using the CLSI (M27-A3) guidelines. The inhibitory concentration 50% (IC₅₀) was calculated using functional analysis with the Graph Pad software.

RESULTS

DES inhibited the growth of all C. albicans strains, whether sensitive or resistant to FLZ. Experimental data fitted non-linear functions of inhibitor concentration versus response. Minimum inhibitory concentrations (MIC) for DES and FLZ were as follows: 28.18µg/ml and 4.90µg/ml (ATCC); 17.16µg/ml and 3.14µg/ml (period); 27.64µg/ml and 4.22µg/ml (2-76); 6.16µg/ml and 438.19µg/ml (12-99), respectively.

CONCLUSIONS

DES showed antifungal activity on all clinical C. albicans strains isolated from patients with dental and medical diseases. It showed the highest potency on the FLZ-resistant isolate.

Effects of tamoxifen on periodontal disease and Candida albicans of patients with breast cancer and other pathologies

Candida albicans is involved in periodontal disease, which is influenced by sex hormones.

AIM

To study the effects of the estrogen antagonist tamoxifen (TAM) on periodontal disease of oncological patients; clinical oral strains of C. albicans.

PATIENTS

With periodontitis and breast cancer and other with AIDS were used.

MATERIALS & METHODS

Periodontal disease was evaluated by the academy of periodontology procedures and the growth of clinical C. albicans isolates were evaluated by the Clinical and Laboratory Standards Institute techniques.

RESULTS

Women who consumed TAM for more than 2 years decreased periodontitis severity. In vitro, TAM inhibited the growth of both fluconazole-sensitive and resistant C. albicans.

CONCLUSION

Administered TAM chronically improves periodontal health and has antifungal activity on oral strains isolated from patients with odontologic and medical pathologies.