Phytochemical Analysis and Antioxidant and Antifungal Activities of Powders, Methanol Extracts, and Essential Oils from Rosmarinus officinalis L. and Thymus ciliatus Desf. Benth.

Chemical residues in food pose health risks such as cancer and liver issues. This has driven the search for safer natural alternatives to synthetic fungicides and preservatives. The aim of this study was to characterize the chemical composition of the essential oils (EO), determine the polyphenolic contents, and evaluate the in vitro antioxidant and antifungal activities of methanol extracts (ME), essential oils (EO), and powders from Rosmarinus officinalis L. (rosemary) and Thymus ciliatus (Desf) Benth. (thyme) from the M'sila region, Algeria. The chemical composition of the EOs was determined by GC-MS. R. officinalis EO was composed of 31 components, mainly camphor (41.22%), camphene (18.14%), and α-pinene (17.49%); T. ciliatus EO was composed of 58 components, mainly, in percentage, α-pinene (22.18), myrcene (13.13), ß-pinene (7.73), ß-caryophyllene (10.21), and germacrene D (9.90). The total phenols and flavonoids were determined spectrophotometrically, and the rosemary ME was found to possess the highest polyphenolic content (127.1 ± 2.40 µg GAE/mg), while the thyme ME had the highest flavonoid content (48.01 ± 0.99 µg QE/mg). The antioxidant activity was assessed using three methods: rosemary ME was the most potent, followed by DPPH (IC50 = 13.43 ± 0.14 µg/mL), ß-carotene/linoleic acid (IC50 = 39.01 ± 2.16 µg/mL), and reducing power (EC50 = 15.03 ± 1.43 µg/mL). Antifungal activity was assessed for 32 pathogenic and foodborne fungi. Four methods were applied to the solid medium. Incorporating the powdered plant into the culture medium (at 10%) reduced the fungal growth to greater than 50% in 21.88% and 6.25% of all fungal isolates, for R. officinalis and T. ciliatus, respectively. The ME, applied by the well diffusion method (0.1 g/mL), was less effective. Different concentrations of EO were tested. Incorporating the EO into the culture medium (1500 µL/L) inhibited 50% of the molds to levels of 50 and 75% for R. officinalis and T. ciliatus, respectively, with the complete inhibition of four fungi. Fumigated EO (15 µL) inhibited 65% of the molds to levels of 65 and 81.25% for R. officinalis and T. ciliatus, respectively, with the complete inhibition of five fungi. There was little to no sporulation in conjunction with the inhibition. Our results revealed some of the potential of the studied plants to fight foodborne molds and presented their promising characteristics as a source of alternatives to chemical pesticides and synthetic preservatives. Further studies are needed to find adequate application techniques in the food safety area.

Protection and Disinfection Activities of Oregano and Thyme Essential Oils Encapsulated in Poly(ε-caprolactone) Nanocapsules.

The biocolonization of building materials by microorganisms is one of the main causes of their degradation. Fungi and bacteria products can have an undesirable impact on human health. The protection and disinfection of sandstone and wood materials are of great interest. In this study, we evaluated the protection and disinfection activity of oregano and thyme essential oils encapsulated in poly(ε-caprolactone) nanocapsules (Or-NCs, Th-NCs) against four types of environmental microorganisms: Pleurotus eryngii, Purpureocillium lilacinum (fungal strains), Pseudomonas vancouverensis, and Flavobacterium sp. (bacterial strains). The surfaces of sandstone and whitewood samples were inoculated with these microorganisms before or after applying Or-NCs and Th-NCs. The concentration-dependent effect of Or-NCs and Th-NCs on biofilm viability was determined by the MTT reduction assay. The results showed that Or-NCs and Th-NCs possess effective disinfection and anti-biofilm activity. Diffuse reflectivity measurements revealed no visible color changes of the materials after the application of the nanoencapsulated essential oils.

Novel Chemical and Biological Insights of Inositol Derivatives in Mediterranean Plants.

Inositols (Ins) are natural compounds largely widespread in plants and animals. Bio-sinthetically they derive from sugars, possessing a molecular structure very similar to the simple sugars, and this aspect concurs to define them as primary metabolites, even though it is much more correct to place them at the boundary between primary and secondary metabolites. This dichotomy is well represented by the fact that as primary metabolites they are essential cellular components in the form of phospholipid derivatives, while as secondary metabolites they are involved in a plethora of signaling pathways playing an important role in the surviving of living organisms. myo-Inositol is the most important and widespread compound of this family, it derives directly from d-glucose, and all known inositols, including stereoisomers and derivatives, are the results of metabolic processes on this unique molecule. In this review, we report the new insights of these compounds and their derivatives concerning their occurrence in Nature with a particular emphasis on the plant of the Mediterranean area, as well as the new developments about their biological effectiveness.

Phenolic Profiles, Antioxidant and Anti-Inflammatory Activities of Hydrodistillation Wastewaters from Five Lamiaceae Species.

Distillation is the most widely used method to obtain an essential oil from plant material. The biomass used in the process is returned as a solid residue together with variable amounts of water rich in water-soluble compounds, which currently are not addressed to any further application. The scope of this work was to evaluate the phytochemical composition of wastewaters coming from hydrodistillation (DWWs) of five aromatic plants belonging to the Lamiaceae family, and to assess their in vitro antioxidant and anti-inflammatory activities. The phenolic profiles of the DWWs were determined by HPLC-DAD and HPLC-ESI/MS. Free radical scavenging ability, oxygen radical antioxidant capacity and superoxide dismutase mimetic activity of the samples under study were measured. Moreover, to investigate the anti-inflammatory activity of the DWWs, an in vitro experimental model of intestinal inflammation was used. The DWW samples' phytochemical analysis allowed the identification of 37 phenolic compounds, all exhibiting good antioxidant and anti-inflammatory activity. Our study contributes to the knowledge on the polyphenolic composition of the DWWs of five aromatic plants of the Lamiaceae family. The results highlight the presence of compounds with proven biological activity, and therefore of great interest in the pharmaceutical and nutraceutical fields.

Origanum vulgare ssp. hirtum (Lamiaceae) Essential Oil Prevents Behavioral and Oxidative Stress Changes in the Scopolamine Zebrafish Model.

Origanum vulgare ssp. hirtum has been used as medicinal herbs promoting antioxidant, anti-inflammatory, antimicrobial, and neuroprotective activities. We investigated the protective effects and the mechanism of O. vulgare ssp. hirtum essential oil (OEO) on cognitive impairment and brain oxidative stress in a scopolamine (Sco)-induced zebrafish (Danio rerio) model of cognitive impairment. Our results show that exposure to Sco (100 µM) leads to anxiety, spatial memory, and response to novelty dysfunctions, whereas the administration of OEO (25, 150, and 300 µL/L, once daily for 13 days) reduced anxiety-like behavior and improved cognitive ability, which was confirmed by behavioral tests, such as the novel tank-diving test (NTT), Y-maze test, and novel object recognition test (NOR) in zebrafish. Additionally, Sco-induced brain oxidative stress and increasing of acetylcholinesterase (AChE) activity were attenuated by the administration of OEO. The gas chromatography-mass spectrometry (GC-MS) analyses were used to elucidate the OEO composition, comprising thymol (38.82%), p-cymene (20.28%), and γ-terpinene (19.58%) as the main identified components. These findings suggest the ability of OEO to revert the Sco-induced cognitive deficits by restoring the cholinergic system activity and brain antioxidant status. Thus, OEO could be used as perspective sources of bioactive compounds, displaying valuable biological activities, with potential pharmaceutical applications.

Oregano and Thyme Essential Oils Encapsulated in Chitosan Nanoparticles as Effective Antimicrobial Agents against Foodborne Pathogens.

The use of natural compounds with biocidal activity to fight the growth of bacteria responsible for foodborne illness is one of the main research challenges in the food sector. This study reports the preparation and physicochemical characterization of chitosan nanoparticles loaded with Thymus capitatus (Th-CNPs) and Origanum vulgare (Or-CNPs) essential oils. The nanosystems were obtained by ionotropic gelation technique with high encapsulation efficiency (80-83%) and loading capacity (26-27%). Nanoparticles showed a spherical shape, bimodal particle size distribution, and good stability (zeta potential values > 40 mV). The treatment of the nanosuspensions at different temperatures (4 and 40 °C) and storage times (7, 15, 21, and 30 days) did not affect their physicochemical parameters and highlights their reservoir ability for essential oils also under stressful conditions. Both Or-CNPs and Th-CNPs exhibited an enhanced bactericidal activity against foodborne pathogens (S. aureus, E. coli, L. monocytogenes) than pure essential oils. These ecofriendly nanosystems could represent a valid alternative to synthetic preservatives and be of interest for health and food safety.

A modified Ising model of Barabási-Albert network with gene-type spins.

The central question of systems biology is to understand how individual components of a biological system such as genes or proteins cooperate in emerging phenotypes resulting in the evolution of diseases. As living cells are open systems in quasi-steady state type equilibrium in continuous exchange with their environment, computational techniques that have been successfully applied in statistical thermodynamics to describe phase transitions may provide new insights to the emerging behavior of biological systems. Here we systematically evaluate the translation of computational techniques from solid-state physics to network models that closely resemble biological networks and develop specific translational rules to tackle problems unique to living systems. We focus on logic models exhibiting only two states in each network node. Motivated by the apparent asymmetry between biological states where an entity exhibits boolean states i.e. is active or inactive, we present an adaptation of symmetric Ising model towards an asymmetric one fitting to living systems here referred to as the modified Ising model with gene-type spins. We analyze phase transitions by Monte Carlo simulations and propose a mean-field solution of a modified Ising model of a network type that closely resembles a real-world network, the Barabási-Albert model of scale-free networks. We show that asymmetric Ising models show similarities to symmetric Ising models with the external field and undergoes a discontinuous phase transition of the first-order and exhibits hysteresis. The simulation setup presented herein can be directly used for any biological network connectivity dataset and is also applicable for other networks that exhibit similar states of activity. The method proposed here is a general statistical method to deal with non-linear large scale models arising in the context of biological systems and is scalable to any network size.

Variability of Hypericins and Hyperforin in Hypericum Species from the Sicilian Flora.

Within Sicilian flora, the genus Hypericum (Guttiferae) includes 10 native species, the most popular of which is H. perforatum. Hypericum's most investigated active compounds belong to naphtodianthrones (hypericin, pseudohypericin) and phloroglucinols (hyperforin, adhyperforin), and the commercial value of the drug is graded according to its total hypericin content. Ethnobotanical sources attribute the therapeutic properties recognized for H. perforatum, also to other Hypericum species. However, their smaller distribution inside the territory suggests that an industrial use of such species, when collected from the wild, would result in an unacceptable depletion of their natural stands. This study investigated about the potential pharmacological properties of 48 accessions from six native species of Hypericum, including H. perforatum and five 'minor' species, also comparing, when possible, wild and cultivated sources. The variability in the content of active metabolites was remarkably high, and the differences within the species were often comparable to the differences among species. No difference was enlightened between wild and cultivated plants. A carefully planned cultivation of Hypericum seems the best option to achieve high and steady biomass yields, but there is a need for phytochemical studies, aimed to identify for multiplication the genotypes with the highest content of the active metabolites.

New Tricks for Old Guys: Recent Developments in the Chemistry, Biochemistry, Applications and Exploitation of Selected Species from the Lamiaceae Family.

Lamiaceae is one of the largest families of flowering plants comprising about 250 genera and over 7,000 species. Most of the plants of this family are aromatic and therefore important source of essential oils. Lamiaceae are widely used as culinary herbs and reported as medicinal plants in several folk traditions. In the Mediterranean area oregano, sage, rosemary, thyme and lavender stand out for geographical diffusion and variety of uses. The aim of this review is to provide recent data dealing with the phytochemical and pharmacological studies, and the more recent applications of the essential oils and the non-volatile phytocomplexes. This literature survey suggests how the deeper understanding of biomolecular processes in the health and food sectors as per as pest control bioremediation of cultural heritage, or interaction with human microbiome, fields, leads to the rediscovery and new potential applications of well-known plants.

Antiproliferative Effect and Cell Cycle Alterations Induced by Salvia officinalis Essential Oil and Its Three Main Components in Human Colon Cancer Cell Lines.

Colon cancer is one of the most common human malignancies, and chemotherapy cannot yet prevent recurrence in all patients. Essential oils are phytocomplexes with antiproliferative properties. In this study, we elucidated the antiproliferative properties and the effect on cell cycle progression of Sicilian Salvia officinalis essential oil and its three main compounds, α-thujone, 1,8-cineole (eucalyptol) and camphor, on three human colon cancer cell lines. The essential oil was obtained by hydrodistillation and analyzed by gas chromatography. Cell proliferation was evaluated by MTT assay, and the cell cycle distribution was determined by flow cytometry. Thirty-four compounds were identified in the tested essential oil. Growth inhibition was observed after 72 h, with an impact on cell cycle progression and no effect on the viability of normal colonic epithelial cells. The study shows that S. officinalis essential oil and its three main components have an in vitro antiproliferative effect on colon cancer cells.

A Two-Year Bio-Agronomic and Chemotaxonomic Evaluation of Wild Sicilian Myrtle (Myrtus communis L.) Berries and Leaves.

A collection of nine Myrtus communis samples from different localities of Sicily was evaluated. Morphological traits and production characteristics have been chosen as parameters to arrange the samples into homogeneous groups and to identify the best biotypes for possible future agro-industrial exploitation. The plant material has been subjected to taxonomic characterization from biometric and phytochemical perspectives. Myrtle berries and leaves have been analyzed for their content in metabolites, applying a cascade extraction protocol for M. communis leaves and a single hydroalcoholic extraction for berries, whereas hydrodistillation procedures have been applied to obtain the essential oils from berries and leaves. The analyses of non-volatile components were carried out by LC-UV-DAD-ESI-MS. All the extracts were characterized by the presence of numerous polyphenols, namely highly hydroxylated flavonols such as quercetin and myricetin; and ellagic acid detected in all samples. In addition, myrtle berries contained nine different anthocyanins, namely delphinidin, petunidin, cyanidin and malvidin derivatives. The essential oils (EOs) were analyzed by a combination of GC-FID and GC/MS. A total of 33 and 34 components were fully characterized with the predominance of α-pinene, myrtenyl acetate, linalool, 1,8-cineole and linalyl acetate. All phytochemical profiles were subjected to cluster analyses, which allowed subdividing the myrtle samples in different chemical groups.

Arbuscular mycorrhizal fungi altered the hypericin, pseudohypericin, and hyperforin content in flowers of Hypericum perforatum grown under contrasting P availability in a highly organic substrate.

St. John's Wort (Hypericum perforatum) is a perennial herb able to produce water-soluble active ingredients (a.i.), mostly in flowers, with a wide range of medicinal and biotechnological uses. However, information about the ability of arbuscular mycorrhizal fungi (AMF) to affect its biomass accumulation, flower production, and concentration of a.i. under contrasting nutrient availability is still scarce. In the present experiment, we evaluated the role of AMF on growth, flower production, and concentration of bioactive secondary metabolites (hypericin, pseudohypericin, and hyperforin) of H. perforatum under contrasting P availability. AMF stimulated the production of aboveground biomass under low P conditions and increased the production of root biomass. AMF almost halved the number of flowers per plant by means of a reduction of the number of flower-bearing stems per plant under high P availability and through a lower number of flowers per stem in the low-P treatment. Flower hyperforin concentration was 17.5% lower in mycorrhizal than in non-mycorrhizal plants. On the contrary, pseudohypericin and hypericin concentrations increased by 166.8 and 279.2%, respectively, with AMF under low P availability, whereas no effect of AMF was found under high P availability. These results have implications for modulating the secondary metabolite production of H. perforatum. However, further studies are needed to evaluate the competition for photosynthates between AMF and flowers at different nutrient availabilities for both plant and AM fungus.

Essential oil composition and antinociceptive activity of Thymus capitatus.

CONTEXT: The essential oil (EO) from Thymus capitatus Hoff. et Link. (Lamiaceae) has been traditionally used for its medicinal properties, such as anti-inflammatory, analgesic, antioxidant and antimicrobial properties. OBJECTIVE: Characterize the constituents from T. capitatus EO and further evaluate the antinociceptive activity by in vivo and in vitro procedures. MATERIALS AND METHODS: Gas chromatography-mass spectrometry was used to identify and quantify the constituents of the T. capitatus EO. The antinociceptive activity was evaluated in vivo by the glutamate-induced nociception model in male Swiss mice (25 g), at doses of 3, 6 and 12 mg/kg, 1 h before evaluation of the licking time response (0-15 min). The mechanism of T. capitatus EO (1-500 µg/mL) on the isolated nerve excitability of Wistar rat (300 g) was assessed by the single sucrose technique. RESULTS AND DISCUSSION: The EO of T. capitatus presented 33 components, mainly monoterpenes and sesquiterpenes, carvacrol (ca. 80%) was its major constituent. T. capitatus EO induced antinociception in orally treated mice (3, 6, and 12 mg/kg) reducing the licking time from control (100.3 ± 11.9 s) to 84.8 ± 12.2, 62.7.6 ± 9.9, and 41.5 ± 12.7 s, respectively (n = 8; p < 0.05). Additionally, we have demonstrated that T. capitatus EO (500 µg/mL) decreased the compound action potential amplitude (VCAP) of about 80.0 ± 4.3% from control recordings (n = 4; p < 0.05). Such activity was presumably mediated through a voltage-gated Na+ channels. CONCLUSIONS: The present study demonstrated the antinociceptive activity of Thymus capitatus essential oil, which acts via peripheral nervous excitability blockade.

Phytochemical, Ecological and Antioxidant Evaluation of Wild Sicilian Thyme: Thymbra capitata (L.) Cav.

In a broad survey conducted throughout the Sicily region, 45 different sites were identified where thyme grows wild. All the biotypes collected were classified as Thymbra capitata (L.) Cav. (syn. Thymus capitatus (L.) Hoffmanns. & Link). Cluster analysis based on the main morphological characteristics of the plant led to the division of the biotypes into 3 major groups. All samples were analyzed for their secondary phytochemical metabolites identified in the extracts and the essential oils. LC-UV-DAD/ESI-MS and GC-FID/GC-MS have been applied to characterize the extracts and the essential oils, respectively. In the extracts, 15 flavonoid derivatives with taxifolin-di-O-glucoside and thymusin as main components, and 2 organic acids, with a large predominance of rosmarinic acid, were identified. On the whole 37 compounds were fully characterized in the essential oils, carvacrol was identified as the main component with an average value of 73.93%. The total phenol content and the antioxidant activity of all phytochemical complexes were determined with the Folin-Ciocalteu (FC) assay, the UV radiation-induced peroxidation in liposomal membranes (UV-IP test), and the scavenging activity of superoxide radical (O2∙-).

Wild Sicilian rosemary: phytochemical and morphological screening and antioxidant activity evaluation of extracts and essential oils.

To identify the best biotypes, an extensive survey of Sicilian wild rosemary was carried out by collecting 57 samples from various sites, followed by taxonomic characterization from an agronomic perspective. All the biotypes collected were classified as Rosmarinus officinalis L. A cluster analysis based on the morphological characteristics of the plants allowed the division of the biotypes into seven main groups, although the characteristics examined were found to be highly similar and not area-dependent. Moreover, all samples were analyzed for their phytochemical content, applying an extraction protocol to obtain the nonvolatile components and hydrodistillation to collect the essential oils for the volatile components. The extracts were characterized by LC-UV-DAD/ESI-MS, and the essential oils by GC-FID and GC/MS analyses. In the nonvolatile fractions, 18 components were identified, namely, 13 flavones, two organic acids, and three diterpenes. In the volatile fractions, a total of 82 components were found, with as predominant components α-pinene and camphene among the monoterpene hydrocarbons and 1,8-cineole, camphor, borneol, and verbenone among the oxygenated monoterpenes. Cluster analyses were carried out on both phytochemical profiles, allowing the separation of the rosemary samples into different chemical groups. Finally, the total phenol content and the antioxidant activity of the essential oils and extracts were determined with the Folin-Ciocalteu (FC) colorimetric assay, the UV radiation-induced peroxidation in liposomal membranes (UV-IP test), and the scavenging activity of the superoxide radical (O$\rm{{_{2}^{{^\cdot} -}}}$). The present study confirmed that the essential oils and organic extracts of the Sicilian rosemary samples analyzed showed a considerable antioxidant/free radical-scavenging activity.

Redox State Modulatory Activity and Cytotoxicity of Olea europaea L. (Oleaceae) Leaves Extract Enriched in Polyphenols Using Macroporous Resin.

The food products derived from Olea europaea are a fundamental part of the Mediterranean diet, and their health-promoting effects are well known. In this study, we analyzed the phytochemical characteristics, the redox state modulatory activity, and the cytotoxic effect of an olive leaf aqueous extract enriched by macroporous resin on different tumor and normal cell lines (LNCaP, PC3, HFF-1). HPLC-DAD analysis, the Folin-Ciocalteu and aluminum chloride methods confirmed the qualitatively and quantitatively high content of phenolic compounds (130.02 ± 2.3 mg GAE/g extract), and a DPPH assay (IC50 = 100.00 ± 1.8 µg/mL), the related antioxidant activity. The biological investigation showed a significant cytotoxic effect, highlighted by an MTT test and the evident cellular morphological changes, on two prostate cancer cell lines. Remarkably, the extract was practically non-toxic on HFF-1 at the concentrations (100, 150, 300 µg/mL) and exposure times tested. Hence, the results are selective for tumor cells. The underlying cytotoxicity was associated with the decrease in ROS production (55% PC3, 42% LNCaP) and the increase in RSH levels (>50% PC3) and an LDH release assay (50% PC3, 40% LNCaP, established necrosis as the main cell death mechanism.

Biomolecular characterization of wild sicilian oregano: phytochemical screening of essential oils and extracts, and evaluation of their antioxidant activities.

An extensive survey of wild Sicilian oregano was made. A total of 57 samples were collected from various sites, followed by taxonomic characterization from an agronomic perspective. Based on morphological and production characteristics obtained from the 57 samples, cluster analysis was used to divide the samples into homogeneous groups, to identify the best biotypes. All samples were analyzed for their phytochemical content, applying a cascade-extraction protocol and hydrodistillation, to obtain the non volatile components and the essential oils, respectively. The extracts contained thirteen polyphenol derivatives, i.e., four flavanones, seven flavones, and two organic acids. Their qualitative and quantitative characterization was carried out by LC/MS analyses. The essential oils were characterized using a combination of GC-FID and GC/MS analyses; a total of 81 components were identified. The major components of the oils were thymol, p-cymene, and γ-terpinene. Cluster analysis was carried out on both phytochemical profiles and resulted in the division of the oregano samples into different chemical groups. The antioxidant activity of the essential oils and extracts was investigated by the Folin-Ciocalteau (FC) colorimetric assay, by UV radiation-induced peroxidation in liposomal membranes (UV-IP test), and by determining the O(2)(∙-)-scavenging activity.

Phytochemical analysis, antibacterial and antifungal effect of Lavandula dentata L. essential oil and methanol extract.

The aim of this study was to analyse the essential oil of Lavandula dentata from Algeria and to test the antioxidant and antimicrobial properties of this plant. The essential oil (EO) (57 constituents) included mainly α-pinene, ß-pinene, nopinone, linalool, cryptone, and limonene. The plant polyphenolic contents and the antioxidant activity were determined. The antimicrobial effect of the EO and the methanolic extract (ME) was assessed against referenced and clinical bacterial strains, and also foodborne fungal isolates. The EO minimal inhibitory concentration (MIC) values varied from 0.25 to 4 mg/mL and minimal bactericidal concentrations (MBCs) were less than 8 mg/mL except for S. aureus, clinical Klebsiella, S. epidermidis, and B. subtilis. The mould strains were significantly inhibited by the EO (87.50% to 88.33%). The MIC values were 3.60-15.62 mg/mL and 0.5-4 mg/mL for ME and EO, respectively. The minimal fungicidal concentration (MFC) values ranged from 31 to 125 mg/mL and from 2 to 8 mg/mL for ME and EO, respectively.

An Integrated In Silico and In Vitro Approach for the Identification of Natural Products Active against SARS-CoV-2.

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has provoked a global health crisis due to the absence of a specific therapeutic agent. 3CLpro (also known as the main protease or Mpro) and PLpro are chymotrypsin-like proteases encoded by the SARS-CoV-2 genome, and play essential roles during the virus lifecycle. Therefore, they are recognized as a prospective therapeutic target in drug discovery against SARS-CoV-2 infection. Thus, this work aims to collectively present potential natural 3CLpro and PLpro inhibitors by in silico simulations and in vitro entry pseudotype-entry models. We screened luteolin-7-O-glucuronide (L7OG), cynarin (CY), folic acid (FA), and rosmarinic acid (RA) molecules against PLpro and 3CLpro through a luminogenic substrate assay. We only reported moderate inhibitory activity on the recombinant 3CLpro and PLpro by L7OG and FA. Afterward, the entry inhibitory activity of L7OG and FA was tested in cell lines transduced with the two different SARS-CoV-2 pseudotypes harboring alpha (α) and omicron (o) spike (S) protein. The results showed that both compounds have a consistent inhibitory activity on the entry for both variants. However, L7OG showed a greater degree of entry inhibition against α-SARS-CoV-2. Molecular modeling studies were used to determine the inhibitory mechanism of the candidate molecules by focusing on their interactions with residues recognized by the protease active site and receptor-binding domain (RBD) of spike SARS-CoV-2. This work allowed us to identify the binding sites of FA and L7OG within the RBD domain in the alpha and omicron variants, demonstrating how FA is active in both variants. We have confidence that future in vivo studies testing the safety and effectiveness of these natural compounds are warranted, given that they are effective against a variant of concerns.