Effects of aqueous fractions of Uncaria tomentosa (Willd.) D.C. on macrophage modulatory activities

Silva-Filho E, Estevinho LM. Antibacterial and Healing Effect of Chicha Gum Hydrogel (Sterculia striata) with Nerolidol

Chicha gum is a natural polymer obtained from the Sterculia striata plant. The hydroxyl groups of its structure have a chemical affinity to form hydrogels, which favors the association with biologically active molecules, such as nerolidol. This association improves the biological properties and allows the material to be used in drug delivery systems. Chicha gum hydrogels associated with nerolidol were produced at two concentrations: 0.01 and 0.02 g mL-1. Then, the hydrogels were characterized by thermogravimetry (TG), Fourier Transform Infrared spectroscopy (FTIR), and rheological analysis. The antibacterial activity was tested against Staphylococcus aureus and Escherichia coli. The cytotoxicity was evaluated against Artemia salina. Finally, an in vivo healing assay was carried out. The infrared characterization indicated that interactions were formed during the gel reticulation. This implies the presence of nerolidol in the regions at 3100-3550 cm-1. The rheological properties changed with an increasing concentration of nerolidol, which resulted in less viscous materials. An antibacterial 83.6% growth inhibition effect was observed using the hydrogel with 0.02 g mL-1 nerolidol. The in vivo healing assay showed the practical activity of the hydrogels in the wound treatment, as the materials promoted efficient re-epithelialization. Therefore, it was concluded that the chicha hydrogels have the potential to be used as wound-healing products.

Medicinal Plants in Peru as a Source of Immunomodulatory Drugs Potentially Useful Against COVID-19

The current COVID-19 pandemic, characterized by a highly contagious severe acute respiratory syndrome, led us to look for medicinal plants as an alternative to obtain new drugs, especially those with immunomodulatory abilities, capable of acting against the pulmonary infection caused by coronavirus 2 (SARS-CoV-2). Despite medical advances with COVID-19 drugs and vaccines, plant-based compounds could provide an array of suitable candidates to test against this virus, or at the very least, to alleviate some symptoms. Therefore, this review explores some plants widely used in Peru that show immunomodulatory properties or, even more, contain phytoconstituents potentially useful to prevent or alleviate the COVID-19 infection. More interestingly, the present review highlights relevant information from those plants to support the development of new drugs to boost the immune system. We used three criteria to choose nine vegetal species, and a descriptive search was then conducted from 1978 to 2021 on different databases, using keywords focused on the immune system that included information such as pharmacological properties, phytochemical, botanical, ethnobotanical uses, and some clinical trials. From these literature data, our results displayed considerable immunomodulation activity along with anti-inflammatory, antiviral, antioxidant, and antitumoral activities. Noticeably, these pharmacological activities are related with a wide variety of bioactive phytoconstituents (mixtures or isolated compounds) which may be beneficial in modulating the overt inflammatory response in severe COVID-19. Further scientific research on the pharmacological activities and clinical utilization of these potential plants are warranted.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s43450-023-00367-w.

The Hydroalcoholic Extract of Uncaria tomentosa (Cat's Claw) Inhibits the Infection of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) In Vitro

The coronavirus disease 2019 (COVID-19) has become a serious problem for public health since it was identified in the province of Wuhan (China) and spread around the world producing high mortality rates and economic losses. Nowadays, the WHO recognizes traditional, complementary, and alternative medicine for treating COVID-19 symptoms. Therefore, we investigated the antiviral potential of the hydroalcoholic extract of Uncaria tomentosa stem bark from Peru against SARS-CoV-2 in vitro. The antiviral activity of U. tomentosa against SARS-CoV-2 in vitro was assessed in Vero E6 cells using cytopathic effect (CPE) and plaque reduction assay. After 48 h of treatment, U. tomentosa showed an inhibition of 92.7% of SARS-CoV-2 at 25.0 μg/mL (p < 0.0001) by plaque reduction assay on Vero E6 cells. In addition, U. tomentosa induced a reduction of 98.6% (p=0.02) and 92.7% (p=0.03) in the CPE caused by SARS-CoV-2 on Vero E6 cells at 25 μg/mL and 12.5 μg/mL, respectively. The EC50 calculated for the U. tomentosa extract by plaque reduction assay was 6.6 μg/mL (4.89–8.85 μg/mL) for a selectivity index of 4.1. The EC50 calculated for the U. tomentosa extract by TCID50 assay was 2.57 μg/mL (1.05–3.75 μg/mL) for a selectivity index of 10.54. These results showed that U. tomentosa, known as cat's claw, has an antiviral effect against SARS-CoV-2, which was observed as a reduction in the viral titer and CPE after 48 h of treatment on Vero E6 cells. Therefore, we hypothesized that U. tomentosa stem bark could be promising in the development of new therapeutic strategies against SARS-CoV-2.

Phthalic anhydride esterified chicha gum: characterization and antibacterial activity

The objective of this research was to modify chicha gum with phthalic anhydride to obtain a new biologically active material. The chemical modification of the gum structure was proven through FTIR, elemental analysis, XRD, TG, and DSC. The derived materials demonstrated excellent inhibitory effect against P. aeruginosa and K. pneumoniae species (rating 100% inhibition) and could also inhibit Escherichia coli growth. The best antimicrobial activity observed for the derivatives suggests that chicha gum hydrophobization due to the addition of phthalic groups improved the interaction of these derivatives with bacterial cell wall components. On the other hand, the derivatives increased CC₅₀ in macrophages but did not present acute toxicity or hemolytic activity, indicating that they are promising for use in prophylaxis or treatment of infections caused by Gram-negative bacteria.

Uncaria tomentosa (cat's claw): a promising herbal medicine against SARS-CoV-2/ACE-2 junction and SARS-CoV-2 spike protein based on molecular modeling

COVID-19 is a novel severe acute respiratory syndrome coronavirus. Currently, there is no effective treatment and vaccines seem to be the solution in the future. Virtual screening of potential drugs against the S protein of severe acute respiratory syndrome corona virus 2 (SARS-CoV-2) has provided small molecular compounds with a high binding affinity. Unfortunately, most of these drugs do not attach with the binding interface of the receptor-binding domain (RBD)–angiotensin-converting enzyme-2 (ACE-2) complex in host cells. Molecular modeling was carried out to evaluate the potential antiviral properties of the components of the medicinal herb Uncaria tomentosa (cat’s claw) focusing on the binding interface of the RBD–ACE-2 and the viral spike protein. The in silico approach starts with protein–ligand docking of 26 Cat’s claw key components followed by molecular dynamics simulations and re-docked calculations. Finally, we carried out drug-likeness calculations for the most qualified cat’s claw components. The structural bioinformatics approaches led to the identification of several bioactive compounds of U. tomentosa with potential therapeutic effect by dual strong interaction with interface of the RBD–ACE-2 and the ACE-2 binding site on SARS-CoV-2 RBD viral spike. In addition, in silico drug-likeness indices for these components were calculated and showed good predicted therapeutic profiles of these phytochemicals found in U. tomentosa (cat’s claw). Our findings suggest the potential effectiveness of cat’s claw as complementary and/or alternative medicine for COVID-19 treatment.

Communicated by Ramaswamy H. Sarma

Antibacterial and cytotoxic properties from esterified Sterculia gum

Sterculia gums, as karaya and chicha gum, are complex branched and polydisperse heteropolysaccharides which can have their applications extended by improving their characteristics through chemical modifications. The objective of this work was to increase the antimicrobial activity of karaya and chicha gum through chemical modification with maleic anhydride. The incorporation of anhydride in the gum structure was confirmed by the characterization techniques. The derived biopolymers were synthesized and characterized by FTIR, X-ray diffraction, Thermogravimetric analysis and elemental analysis. Antimicrobial activity was evaluated against the Staphylococcus aureus strain (ATCC 25923). Mammalian cytotoxicity assays were also performed by MTT and hemolysis tests. The derivatives showed excellent antibacterial action inhibiting almost 100% of bacterial growth and did not present significant cytotoxicity in mammalian cells. The results showed that the derivatives are promising for biomedical applications aiming the control of infectious diseases caused by S. aureus.

In vitro synergism of a water insoluble fraction of Uncaria tomentosa combined with fluconazole and terbinafine against resistant non-Candida albicans isolates

CONTEXT

Uncaria tomentosa D.C. (Rubiaceae) has several biological activities, including activity against resistant Candida strains. The synergistic interaction with terbinafine or fluconazole can be an important alternative to overcome this resistance.

OBJECTIVES

The potential synergy between a water insoluble fraction (WIF) from Uncaria tomentosa bark and the antifungals terbinafine (TRB) and fluconazole (FLZ) against non-Candida albicans resistant strains was investigated.

MATERIALS AND METHODS

TRB and FLZ, alone and combined with WIF, were tested by the checkerboard procedure using the micro-dilution technique against seven isolates of Candida glabrata and C. krusei. The molecular interactions occurring outside the cell wall were evaluated by scanning electron microscopy, Fourier transform infrared (FT-IR) and differential scanning calorimetry (DSC) analysis.

RESULTS

The checkerboard inhibitory assay demonstrated synergy for WIF:TRB and WIF:FLZ combinations, respectively. The best synergistic cell damage was demonstrated unequivocally for the associations of WIF and TRB (1.95:4.0 μg/mL) and WIF and FLZ (1.95:8.0 μg/mL). The comparison of the FT-IR spectra of the antifungal alone, and in combination with WIF, allows recognizing clear differences in 3000, 1600, 1400, and 700-800 cm^-1 bands. Additionally, modifications on TRB and FLZ thermograms were clearly noticed after their combination with WIF.

CONCLUSIONS

DSC and infrared analysis demonstrated intermolecular interactions between WIF and either TRB or FLZ. Hence, quite likely the synergistic effect is related to interaction events occurring outside the cell wall between antifungal and cat's claw proanthocyanidins. A direct action on the cell wall is suggested, without connection with the ABC efflux pump mechanism.

Medicinal Plants from Mexico, Central America, and the Caribbean Used as Immunostimulants

A literature review was undertaken by analyzing distinguished books, undergraduate and postgraduate theses, and peer-reviewed scientific articles and by consulting worldwide accepted scientific databases, such as SCOPUS, Web of Science, SCIELO, Medline, and Google Scholar. Medicinal plants used as immunostimulants were classified into two categories: (1) plants with pharmacological studies and (2) plants without pharmacological research. Medicinal plants with pharmacological studies of their immunostimulatory properties were subclassified into four groups as follows: (a) plant extracts evaluated for in vitro effects, (b) plant extracts with documented in vivo effects, (c) active compounds tested on in vitro studies, and (d) active compounds assayed in animal models. Pharmacological studies have been conducted on 29 of the plants, including extracts and compounds, whereas 75 plants lack pharmacological studies regarding their immunostimulatory activity. Medicinal plants were experimentally studied in vitro (19 plants) and in vivo (8 plants). A total of 12 compounds isolated from medicinal plants used as immunostimulants have been tested using in vitro (11 compounds) and in vivo (2 compounds) assays. This review clearly indicates the need to perform scientific studies with medicinal flora from Mexico, Central America, and the Caribbean, to obtain new immunostimulatory agents.

Schisandra polysaccharide evokes immunomodulatory activity through TLR 4-mediated activation of macrophages

Schisandra chinensis (Turcz.) Baill has been used in traditional Chinese medicine for centuries. Previous studies have shown that Schisandra polysaccharide (SCPP11) has robust antitumor activity in vivo. In this study, the immunomodulatory activity and mechanisms of action of SCPP11 were investigated further to reveal its mechanism of action against tumors. Results showed that SCPP11 increased the thymus and spleen indices, pinocytic activity of peritoneal macrophages, and hemolysin formation in CTX-induced immunosuppressed mice. Moreover, SCPP11 significantly increased immunoglobulin levels, cytokines levels in vivo and induced RAW264.7 cells to secrete cytokines in vitro. RAW264.7 cells pretreated with SCPP11 significantly inhibited the proliferation of HepG-2 cells. In addition, SCPP11 promoted both the expression of iNOS protein and of iNOS and TNF-α mRNA. TLR-4 is a possible receptor for SCPP11-mediated macrophage activation. Therefore, the data suggest that SCPP11 exerted its antitumor activity by improving immune system functions through TLR-4-mediated up-regulation of NO and TNF-α.