Special Issue "Bioactive Compounds from Natural Sources (2020, 2021)"

Amoebicidal thymol analogues against brain-eating amoeba, Naegleria fowleri

Naegleria fowleri, known as the brain-eating amoeba, is the pathogen parasite that causes primary amoebic meningoencephalitis. None of the currently available therapies are fully effective, mainly due to the inefficacy of pharmacotherapy. In this regard, natural products and related compounds represent a promising strategy for amoebicidal drug discovery. Herein, a series of eight monoterpene phenol derivatives of thymol bearing ester, carbonate, or carbamate moieties were prepared, and screened as potential amoebicidal agents on N. fowleri. The cytotoxicity of these compounds on murine macrophages cell line J774 was also evaluated to assess their selectivity. Compounds 3, 4, 7 and 8 showed significant activity against the N. fowleri trophozoite. Moreover, 4-nitrophenyl thymyl carbonate 8 displayed the highest potency, showing IC50 values of 22.87 and 25.16 μM against N. fowleri trophozoite and cyst stages, respectively, coupled with low cytotoxicity on a mammal cell line. Furthermore, mechanism of action studies revealed that derivative 8 triggered programmed cell death via cytosolic calcium accumulation, mitochondrial alteration, membrane damage, chromatin condensation, and ROS accumulation. In addition, the in-silico ADME analysis indicated that derivative 8 exhibits exceptional drug-likeness meeting all the pharmacokinetic criteria. These results highlight derivative 8 as a promising amoebicidal agent to develop new drugs for the treatment of Naegleria infections.

Exploring the antimicrobial and antibiofilm potency of four essential oils against selected human pathogens using in vitro and in silico approaches

Multi-drug-resistant (MDR) pathogens pose a significant global health challenge, underscoring the urgent need for novel antimicrobial agents with minimal toxicity to humans. This study investigated the in vitro and in silico antimicrobial and antibiofilm potentials of four essential oils (EOs): clove bud oil (CBO; Syzygium aromaticum L.), black seed oil (BSO; Nigella sativa L.), cinnamon bark oil (CNBO; Cinnamomum zeylanicum), and citronella oil (CTLO; Cymbopogon nardus L.), against 19 selected human pathogens, including MDR strains. Among the tested EOs, CBO, BSO, and CNBO exhibited the highest antibacterial activity against Staphylococcus epidermidis, with the mean zone of inhibition diameters (ZIDs) of 20.0 ±  0.2 mm, 46.0 ±  0.3 mm, and 32.0 ±  0.1 mm, respectively, at a concentration of 10 µL/disc, while CTLO displayed no antibacterial activity. CNBO demonstrated superior antifungal activity, with the mean ZIDs of 49.0 ±  0.3 mm and 36.0 ±  0.3 mm for Candida albicans and Aspergillus niger, respectively. Molecular docking analyses revealed robust interactions of key bioactive compounds-eugenol (EU) from CBO, thymoquinone (TQ) from BSO, cinnamaldehyde (CN) from CNBO, citronellal (CIT) and linalool (LIN) from CTLO-with microbial target proteins, substantiating their antimicrobial and antibiofilm potential. Notably, CTLO, despite limited in vitro activity, exhibited unique binding interactions in silico, suggesting potential niche applications. These findings underscore the translational potential of EOs as alternative antimicrobial therapies against MDR infections, particularly biofilm-associated infections, and highlight the need for further in vivo studies to validate their efficacy and safety.

Global Status, Recent Trends, and Knowledge Mapping of Olive Bioactivity Research Through Bibliometric Analysis (2000-2024)

Over the past two decades, both academic and industrial interest in olive bioactive compounds has grown significantly due to their remarkable health benefits, such as antioxidant, anti-inflammatory, and cardioprotective properties. These compounds, found in both olive fruit and leaves, have become a central focus in the research on functional foods and nutraceuticals. A comprehensive bibliometric analysis of scientific publications from 2000 to 2024 highlights a notable increase in this field, with 2228 documents published in high-impact journals with an estimated annual growth rate of 0.2694 year-1, particularly in the last decade. This surge reflects the growing recognition of olive bioactive compounds' potential in promoting human health through nutritional and therapeutic interventions, and their role in the expanding nutraceutical industry. This growth is further reaffirmed by patent analysis, which shows a significant rise in industrial interest and patent filings related to olive bioactive compounds. The analysis also examined nearly 6000 keywords to identify the most influential research domains, pinpoint knowledge gaps, and reveal the most important bioactive compounds in olives and their potential in preventing various human diseases.

HSCCC Straightforward Fast Preparative Method for Isolation of Two Major Cytotoxic Withanolides from Athenaea fasciculata (Vell.) I.M.C. Rodrigues & Stehmann

Athenaea fasciculata belongs to the Solanaceae family and is a promising source of cytotoxic withanolides known as aurelianolides A and B. In the last years, the pharmacological studies of these aurelianolides on different leukemia cell lines have stimulated new studies on their potential as alternative candidates for new lead anticancer drugs. However, the obtention of these two pure compounds by traditional preparative is a costly and long time-consuming process, which is performed in several steps. This study aimed to propose a straightforward approach for isolating aurelianolides A and B using high-speed countercurrent chromatography (HSCCC). In this study, among 10 different solvent systems, the system composed of n-hexane/ethyl acetate/methanol/water 3:6:2:1 (v/v/v/v) was chosen for optimization. This HEMWat system was optimized to 4:8:2:4 (v/v/v/v) and chosen for HSCCC separation in a tail-to-head elution mode. After the HSCCC scale-up procedure, a withanolides mixture (200.0 mg) was separated within 160 min in a single-step purification process. In total, 78.9 mg of aurelianolide A (up to 95.0% purity) and 54.3 mg of aurelianolide B (up to 88.5% purity) was obtained by this fast sequential liquid-liquid partition process. The isolated withanolides were identified by 1H and 13C NMR spectroscopy (this method has proven to be faster and more efficient than classical procedures (CC and Prep-TLC)).

Evaluating the Anti-Osteoporotic Potential of Mediterranean Medicinal Plants: A Review of Current Evidence

Background: Bones are biological reservoirs for minerals and cells, offering protection to the other organs and contributing to the structural form of the body. Osteoporosis is a prevalent bone condition that significantly impacts people's quality of life. Treatments utilizing natural products and medicinal plants have gained important attention in the management of osteoporosis and its associated implications, such as osteoporotic fractures. Even though thousands of plants grow in the Mediterranean region, the use of medicinal plants as an alternative therapy for osteoporosis is still limited. Methods: This article provides a comprehensive overview of seven Mediterranean medicinal plants that are used in osteoporosis and osteoporotic fractures in in vitro, in vivo, and clinical trials. The mechanism of action of the medicinal plants and their bioactive compounds against diseases are also briefly discussed. Results: The findings clearly indicate the ability of the seven medicinal plants (Ammi majus, Brassica oleracea, Ceratonia siliqua L., Foeniculum vulgare, Glycyrrhiza glabra, Salvia officinalis, and Silybum marianum) as anti-osteoporosis agents. Xanthotoxin, polyphenols, liquiritin, formononetin, silymarin, and silibinin/silybin were the main bioactive compounds that contributed to the action against osteoporosis and osteoporotic fractures. Conclusions: In this review, the Mediterranean medicinal plants prove their ability as an alternative agent for osteoporosis and osteoporotic fractures instead of conventional synthetic therapies. Thus, this can encourage researchers to delve deeper into this field and develop medicinal-plant-based drugs.

A Reliable Multifaceted Solution against Foodborne Viral Infections: The Case of RiLK1 Decapeptide

Food-borne transmission is a recognized route for many viruses associated with gastrointestinal, hepatic, or neurological diseases. Therefore, it is essential to identify new bioactive compounds with broad-spectrum antiviral activity to exploit innovative solutions against these hazards. Recently, antimicrobial peptides (AMPs) have been recognized as promising antiviral agents. Indeed, while the antibacterial and antifungal effects of these molecules have been widely reported, their use as potential antiviral agents has not yet been fully investigated. Herein, the antiviral activity of previously identified or newly designed AMPs was evaluated against the non-enveloped RNA viruses, hepatitis A virus (HAV) and murine norovirus (MNV), a surrogate for human norovirus. Moreover, specific assays were performed to recognize at which stage of the viral infection cycle the peptides could function. The results showed that almost all peptides displayed virucidal effects, with about 90% of infectivity reduction in HAV or MNV. However, the decapeptide RiLK1 demonstrated, together with its antibacterial and antifungal properties, a notable reduction in viral infection for both HAV and MNV, possibly through direct interaction with viral particles causing their damage or hindering the recognition of cellular receptors. Hence, RiLK1 could represent a versatile antimicrobial agent effective against various foodborne pathogens including viruses, bacteria, and fungi.

Antimicrobial peptides for novel antiviral strategies in the current post-COVID-19 pandemic

The recent pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has highlighted how urgent and necessary the discovery of new antiviral compounds is for novel therapeutic approaches. Among the various classes of molecules with antiviral activity, antimicrobial peptides (AMPs) of innate immunity are among the most promising ones, mainly due to their different mechanisms of action against viruses and additional biological properties. In this review, the main physicochemical characteristics of AMPs are described, with particular interest toward peptides derived from amphibian skin. Living in aquatic and terrestrial environments, amphibians are one of the richest sources of AMPs with different primary and secondary structures. Besides describing the various antiviral activities of these peptides and the underlying mechanism, this review aims at emphasizing the high potential of these small molecules for the development of new antiviral agents that likely reduce the selection of resistant strains.

Unraveling the Neuroprotective Effect of Natural Bioactive Compounds Involved in the Modulation of Ischemic Stroke by Network Pharmacology

Ischemic stroke (IS) is one of the leading causes of mortality worldwide. It is characterized by the partial or total occlusion of arteries that supply blood to the brain, leading to the death of brain cells. In recent years, natural bioactive compounds (NBCs) have shown properties that ameliorate the injury after IS and improve the patient's outcome, which has proven to be a potential therapeutic strategy due to their neuroprotective effects. Hence, in the present study, we use both systems pharmacology and chemoinformatic analyses to identify which NBCs have the most potential to be used against IS in clinics. Our results identify that flavonoids and terpenoids are the most studied NBCs, and, mainly, salidrosides, ginkgolides A, B, C, and K, cordycepin, curcumin, baicalin, resveratrol, fucose, and cannabidiol, target the main pathological processes occurring in IS. However, the medicinal chemistry properties of such compounds demonstrate that only six fulfill such criteria. However, only cordycepin and salidroside possess properties as leader molecules, suggesting that these compounds may be considered in developing novel drugs against IS.

In vitro antioxidant and free-radical scavenging activities of polar leaf extracts of Vernonia amygdalina

BACKGROUND

Plants are able to deliver a huge number of differing bioactive compounds which may supplement the requirements of the human body by acting as natural antioxidants. Antioxidants are mindful for the defense component of the life form against the pathologies related to the assault of free radicals. The main purpose of this study was to investigate the qualitative phytochemical composition of Vernonia amygdalina leaf extract and its antioxidant activity.

METHOD

The powdered plant sample was successively extracted with aqueous, methanol and ethanol solvents using Soxhlet apparatus. The antioxidant activities of the crude leaf extract were determined using 1, 1- diphenyl-2-picryl hydrazyl (DPPH) radical, 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) radical, phosphomolybdate (PM) and hydrogen peroxide (H₂O₂) scavenging assay. All the examinations were drained triplicates and average values of each test were taken.

RESULTS

Phytochemical investigation of the plant revealed that the three solvent extracts contained numerous bioactive compounds namely alkaloids, tannins, saponins, phenols, terpenoids, steroids, glycosides and sugars. The result showed that, the leaf extracts of V. amygdalina obtained from methanol extract exhibit the maximum antioxidant activity compared ethanol and aqueous extracts. The IC50 values of DPPH assay for the H₂O, MeOH and EtOH extracts were 111.4, 94.92 and 94.83 μg/ml; of ABTS assay were 334.3, 179.8 and 256.9 μg/ml; of H₂O₂ assay were 141.6, 156 and 180.6 μg/ml, respectively. The maximum radical scavenging activity was obtained in DPPH assay while the lowest scavenging activity was obtained in ABTS assay method. The data obtained in the in vitro models clearly suggest that methanol extract has higher antioxidant activity due to a higher presence of phenolic constituents in the extract.

CONCLUSION

This study revealed that V. amygdalina leaf has a noteworthy antioxidant and free radical scavenging activity mitigating the traditional use of the plant for different aliments.