Comprehensive Secondary Metabolite Profiling and Antioxidant Activity of Aqueous and Ethanol Extracts of Neolamarckia cadamba (Roxb.) Bosser Fruits

BACKGROUND

Neolamarckia cadamba (Rubiaceae) is a well-recognized medicinal plant with recorded therapeutical attributes. However, a thorough assessment of active compounds in its fruits is lacking, limiting their use and valorization in pharmacological industries.

METHODS

Thus, this study investigated variations in the fruits' secondary metabolite (SM) profiles, as well as antioxidant activities in aqueous (WA) and ethanol (ET) extracts.

RESULTS

Liquid chromatography-electrospray ionization tandem mass spectrometry identified 541 SMs, of which 14 and 1 (di-O-glucosylquinic acid) were specifically detected in ET and WA, respectively. Phenolic acids (36.97%), flavonoids (28.10%), terpenoids (12.20%), and alkaloids (9.98%) were the dominant SMs. The SM profiles of the fruits in WA and ET were quite different. We revealed 198 differentially extracted (DE) metabolites between WA and ET, including 62 flavonoids, 57 phenolic acids, 45 terpenoids, 14 alkaloids, etc. Most DE flavones (36 out of 40), terpenoids (45 out of 45), and alkaloids (12 out of 14) had higher content in ET. Catechin and its derivatives, procyanidins, and tannins had higher content in WA. ABTS and DPPH assays showed that the antioxidant activity of ET was significantly higher than that of WA.

CONCLUSIONS

Our findings will facilitate the efficient extraction and evaluation of specific active compounds in N. cadamba.

Antimicrobial Activities of Natural Bioactive Polyphenols

Secondary metabolites, polyphenols, are widespread in the entire kingdom of plants. They contain one or more hydroxyl groups that have a variety of biological functions in the natural environment. These uses include polyphenols in food, beauty products, dietary supplements, and medicinal products and have grown rapidly during the past 20 years. Antimicrobial polyphenols are described together with their sources, classes, and subclasses. Polyphenols are found in different sources, such as dark chocolate, olive oil, red wine, almonds, cashews, walnuts, berries, green tea, apples, artichokes, mushrooms, etc. Examples of benefits are antiallergic, antioxidant, anticancer agents, anti-inflammatory, antihypertensive, and antimicrobe properties. From these sources, different classes of polyphenols are helpful for the growth of internal functional systems of the human body, providing healthy fats, vitamins, and minerals, lowering the risk of cardiovascular diseases, improving brain health, and rebooting our cellular microbiome health by mitochondrial uncoupling. Among the various health benefits of polyphenols (curcumin, naringenin, quercetin, catechin, etc.) primarily different antimicrobial activities are discussed along with possible future applications. For polyphenols and antimicrobial agents to be proven safe, adverse health impacts must be substantiated by reliable scientific research as well as in vitro and in vivo clinical data. Future research may be influenced by this evaluation.

Improved anti-cancer effects of luteolin@ZIF-8 in cervical and prostate cancer cell lines

Luteolin, a naturally occurring pharmaceutical compound with significant antitumor properties, faces challenges in clinical applications due to its low solubility in water and limited bioavailability. To address these issues, a one-step synthesis method was employed to encapsulate luteolin within ZIF-8. The successful preparation of luteolin@ ZIF-8 nanoparticles was confirmed through various analytical techniques, including fourier-transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), laser size distribution analysis, X-ray diffraction (XRD), and release curve assessment. Results indicate that the formulated luteolin@ ZIF-8 nanoparticles exhibited high drug loading (1360 mg/g) and demonstrated selective drug release in acidic microenvironments. Furthermore, the encapsulation of luteolin increased the size of ZIF-8 from 168.4 ± 0.2 nm to 384.7 ± 1.4 nm, but did not change its crystalline structure significantly. Notably, the results of in vitro anti-cervical and prostate cancers experiments revealed that luteolin@ ZIF-8 had better efficacy in inhibiting the proliferation and migration of HeLa and PC3 cells than free luteolin. The antitumor activity of luteolin@ ZIF-8 was sustained for 72 h, with a particularly pronounced inhibitory effect on HeLa cells as compared to PC3 cells. This study underscores the effective enhancement of luteolin's antitumor activity through encapsulation in ZIF-8, offering substantial implications for improving its clinical applications.

Flavonoids in the Spotlight: Bridging the Gap between Physicochemical Properties and Formulation Strategies

Flavonoids are hydroxylated polyphenols that are widely distributed in plants with diverse health benefits. Despite their popularity, the bioavailability of flavonoids is often overlooked, impacting their efficacy and the comparison of products. The study discusses the bioavailability-related physicochemical properties of flavonoids, with a focus on the poorly soluble compounds commonly found in dietary supplements and herbal products. This review sums up the values of pKa, log P, solubility, permeability, and melting temperature of flavonoids. Experimental and calculated data were compiled for various flavonoid subclasses, revealing variations in their physicochemical properties. The investigation highlights the challenges posed by poorly soluble flavonoids and underscores the need for enabling formulation approaches to enhance their bioavailability and therapeutic potential. Compared to aglycones, flavonoid glycosides (with sugar moieties) tend to be more hydrophilic. Most of the reviewed aglycones and glycosides exhibit relatively low log P and high melting points, making them "brick dust" candidates. To improve solubility and absorption, strategies like size reduction, the potential use of solid dispersions and carriers, as well as lipid-based formulations have been discussed.

Efficient Recovery Strategy of Luteolin from Agricultural Waste Peanut Shells and Activity Evaluation of Its Functional Biomolecules

Peanut shells (PSs) generated from agricultural waste contain valuable compounds with bioactive properties such as anti-aging, antimicrobial, and antioxidant properties, making it desirable to recycle them as a sustainable resource. The aim of this study is to design an effective luteolin recovery process as the first step of an integrated biorefinery utilizing PSs as raw material. The major extraction variables and their ranges for luteolin recovery from PSs were determined (0-60 °C, 1-5 h, 0-100% MeOH concentration) and a predictive model was derived through a response surface methodology (RSM). Based on the predictive model, the equation determined for the maximal extraction of luteolin at 1 h was as follows: y = -1.8475x + 159.57, and the significant range of variables was as follows: 33.8 °C ≤ temperature (x) ≤ 48.5 °C and 70.0% ≤ MeOH concentration (y) ≤ 97.5%, respectively. High antioxidant and elastase inhibitory activities of PS extracts were confirmed, and these results support their potential to be used as functional materials. In addition, 39.2% of the solid residue after extraction was carbohydrate, which has potential as a carbon source for fermentation. This study provides a useful direction on an integrated biorefinery approach for sustainable agricultural waste valorization.

Optimization of a Luteolin-Loaded TPGS/Poloxamer 407 Nanomicelle: The Effects of Copolymers, Hydration Temperature and Duration, and Freezing Temperature on Encapsulation Efficiency, Particle Size, and Solubility

BACKGROUND

Luteolin is a flavonoid compound that has been widely studied for its various anti-cancer properties and sensitization to multidrug-resistant cells. However, the limited solubility and bioavailability of Lut hindered its potential clinical use. Theoretically, the combination of this compound with vitamin E TPGS and poloxamer 407 can produce a synergistic effect to enhance tumor apoptosis and P-glycoprotein inhibition. This study aimed to develop and optimize vitamin E TPGS/Poloxamer 407 micelles loaded with luteolin through investigating certain factors that can affect the encapsulation efficiency and particle size of the micelle.

METHODS

A micelle was prepared using the film hydration method, and the micellar solution was lyophilized. The cake formed was analyzed. The factors investigated include the concentrations of the surfactants, ratio of vitamin E TPGS/Poloxamer 407, temperature of the hydrating solution, duration of hydration, and freezing temperature before lyophilization. The effects of these factors on the encapsulation efficiency and particle size of the micelle were also studied. The encapsulation efficiency was measured using a UV-Vis spectrophotometer, while particle size was measured using dynamic light scattering.

RESULTS

The optimized micelle was found to have 90% encapsulation efficiency with a particle size of less than 40 nm, which was achieved using a 10% concentration of surfactants at a vitamin E TPGS/Poloxamer 407 ratio of 3:1. The optimized temperature for hydrating the micellar film was 40 °C, the optimized mixing time was 1 h, and the optimized freezing temperature was -80 °C. The solubility of the luteolin-loaded micelles increased 459-fold compared to pure Lut in water. The critical micelle concentration of the vitamin E TPGS/Poloxamer 407 micelle was 0.001 mg/mL, and the release study showed that luteolin-loaded micelles exhibited sustained release behavior. The release of luteolin from a micelle was found to be higher in pH 6.8 compared to pH 7.4, which signified that luteolin could be accumulated more in a tumor microenvironment compared to blood.

CONCLUSION

This study demonstrated that several factors need to be considered when developing such nanoparticles in order to obtain a well-optimized micelle.

Rapid quantitative detection of luteolin using an electrochemical sensor based on electrospinning of carbon nanofibers doped with single-walled carbon nanoangles

In this study, single-walled carbon nanoangles/carbon nanofibers (SWCNHs/CNFs) were synthesized by electrospinning, followed by annealing in a N₂ atmosphere. The synthesized composite was structurally characterized by scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. The electrochemical sensor was fabricated by modifying a glassy carbon electrode (GCE) for luteolin detection, and its electrochemical characteristics were investigated using differential pulse voltammetry, cyclic voltammetry, and chronocoulometry. Under optimized conditions, the response range of the electrochemical sensor to luteolin was 0.01-50 μM, and the detection limit was 3.714 nM (S/N = 3). The SWCNHs/CNFs/GCE sensor showed excellent selectivity, repeatability, and reproducibility, thus enabling the development of an economical and practical electrochemical method for the detection of luteolin.

CID12261165, a flavonoid compound as antibacterial agents against quinolone-resistant Staphylococcus aureus

Flavonoids are plant-produced secondary metabolites that are found ubiquitously. We have previously reported that apigenin, a class of flavonoid, has unique antimicrobial activity against Staphylococcus aureus (S. aureus), one of the major human pathogens. Apigenin inhibited fluoroquinolone-resistant S. aureus with DNA gyrase harboring the quinolone-resistant S84L mutation but did not inhibit wild-type DNA gyrase. In this study, we describe five flavonoids, quercetin, luteolin, kaempferol, baicalein, and commercially available CID12261165, that show similar antimicrobial activity against fluoroquinolone-resistant S. aureus. Among them, CID12261165 was the most effective with MIC values of ≤ 4 mg/L against quinolone-resistant S. aureus strains. In vitro DNA cleavage and supercoiling assays demonstrated inhibitory activity of CID12261165 against mutated DNA gyrase, whereas activity against wild-type DNA gyrase was not observed. CID12261165 also inhibited quinolone-resistant Enterococci with an MIC value of 8 mg/L. While fluoroquinolone-resistant amino acid replacements can improve the fitness of bacterial cells, it is unknown why quinolone-susceptible S. aureus strains were predominant before the introduction of fluoroquinolone. The present study discusses the current discrepancies in the interpretation of antimicrobial activities of flavonoids, as well as the possible reasons for the preservation of wild-type DNA gyrase wherein the environmental flavonoids cannot be ignored.

Mechanistic Insights into Luteolin-Loaded Elastic Liposomes for Transdermal Delivery: HSPiP Predictive Parameters and Instrument-Based Evidence

We evaluated mechanistic insights into luteolin (LUT)-loaded elastic liposomes (OLEL1) permeated across rat skin. HSPiP software-based parameters, thermal analysis, infrared analysis, and morphological evaluations were employed to understand mechanistic observations of drug permeation and deposition. HSPiP provided HSP values (δ_d, δ_p, and δ_h) of OLEL1 (based on composition), LUT, excipients, and rat skin (literature value and by-default value). Rat skin was studied via Fourier transform infrared (FTIR), differential scanning calorimetry (DSC), fluorescence microscopy, scanning electron microscopy (SEM), and atomic force microscopy (AFM) studies. The δ_d and δ_h estimation of the skin and phosphatidylcholine showed close relation in terms of δ_d and δ_h. Similarly, OLEL1 and the skin might interact with each other mainly through δ_d and δ_p forces as evidenced by the predicted values. The untreated skin showed characteristic stretching and vibrations as compared to lower frequencies caused by OLEL1. DSC showed changes in the thermal behavior of the skin after OLEL1 treatment as compared to the untreated skin. Visualization of these changes was evident under fluorescence microscopy and SEM for confirmed substantial reversible surface perturbation of the skin protein layer for improved vesicle permeation and subsequent internalization with the inner skin matrix. The AFM study confirmed the nanoscale surface roughness variation caused substantially by OLEL1 and OLEL1 placebo as compared to the untreated control and drug solution. Thus, the study clearly demonstrated mechanistic insights into LUT-loaded vesicles across rat skin for enhanced permeation and drug deposition.

Self-Emulsifying Phospholipid Preconcentrates for the Enhanced Photoprotection of Luteolin

Exposure to ultraviolet B (UVB) leads to the overproduction of reactive oxygen species (ROS), causing higher risks of skin disorders. Luteolin (Lut) is a naturally occurring antioxidant that can absorb a broad range of ultraviolet light, but its water solubility and skin permeability are limited and insufficient. The aim of the current study was to develop a Lut-loaded self-emulsifying phospholipid preconcentrate (LSEPP) for enhancing the solubility, permeability, and photoprotective activity of Lut. The designed formulations were firstly examined for their droplet size, zeta potential, dispersity, and in vitro corneum permeability after dispensing the preconcentrate to form an emulsion; the optimized formulation was further characterized for its emulsified morphology, compatibility with excipients, stability in the preconcentrate form, and photoprotective activity by the HaCaT cell model under the emulsified status. The optimized LSEPP formulation attained a smaller droplet size (140.6 ± 24.2 nm) with the addition of 1,8-cineole and increased the permeability of Lut by 7-fold. As evidenced in the cell model studies, the optimized LSEPP formulation can efficiently deliver Lut into HaCaT cells after emulsification and result in a 115% better cell viability as well as a 203% stronger ROS scavenging capability, compared with those of unformulated Lut after UVB irradiation. To sum up, we have successfully developed an LSEPP formulation, which is a safe and promising topical delivery system for enhancing the photoprotective effects of Lut.