(1) Background: Viral respiratory infections cause life-threatening diseases in millions of people worldwide every year. Human coronavirus and several picornaviruses are responsible for worldwide epidemic outbreaks, thus representing a heavy burden to their hosts. In the absence of specific treatments for human viral infections, natural products offer an alternative in terms of innovative drug therapies. (2) Methods: We analyzed the antiviral properties of the leaves and stem bark of the mulberry tree (Morus spp.). We compared the antiviral activity of Morus spp. on enveloped and nonenveloped viral pathogens, such as human coronavirus (HCoV 229E) and different members of the Picornaviridae family—human poliovirus 1, human parechovirus 1 and 3, and human echovirus 11. The antiviral activity of 12 water and water–alcohol plant extracts of the leaves and stem bark of three different species of mulberry—Morus alba var. alba, Morus alba var. rosa, and Morus rubra—were evaluated. We also evaluated the antiviral activities of kuwanon G against HCoV-229E. (3) Results: Our results showed that several extracts reduced the viral titer and cytopathogenic effects (CPE). Leaves’ water-alcohol extracts exhibited maximum antiviral activity on human coronavirus, while stem bark and leaves’ water and water-alcohol extracts were the most effective on picornaviruses. (4) Conclusions: The analysis of the antiviral activities of Morus spp. offer promising applications in antiviral strategies.

Water extract of Acacia seyal bark is used traditionally by the population in Djibouti for its anti-infectious activity. The evaluation of in vitro antibacterial, antioxidant activities and cytotoxicity as well as chemical characterization of Acacia seyal bark water and methanolic extracts were presented. The water extract has a toxicity against the MRC-5 cells at 256 μg/mL while the methanolic extract has a weak toxicity at the same concentration. The methanolic extract has a strong antioxidant activity with half maximal inhibitory concentration (IC₅₀) of 150 ± 2.2 μg/mL using 1-diphenyl-2-picrylhydrazyl (DPPH) and IC₅₀ of 27 ± 1.3 μg/mL using 2,2′-azino-bis 3-ethylbenzthiazoline-6-sulphonic acid (ABTS) radical methods. For ferric reducing/antioxidant power (FRAP) assay, the result is 45.74 ± 5.96 μg Vitamin C Equivalent (VCE)/g of dry weight (DW). The precipitation of tannins from methanol crude extract decreases the MIC from 64 µg/mL to 32 µg/mL against Staphylococcus aureus and Corynebacterium urealyticum. However, the antioxidant activity is higher before tannins precipitation than after (IC₅₀ = 150 µg/mL for methanolic crude extract and 250 µg/mL after tannins precipitation determined by DPPH method). By matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) analysis, the results showed that the condensed tannins consist of two types of catechin and gallocatechin-based oligomers. The fractionation led to the identification of three pure compounds: two flavanols catechin and epicatechin; one triterpene as lupeol; and a mixture of three steroids and one fatty acid: campesterol, stigmasterol, clionasterol, and oleamide.

The chemical composition of the essential oils of two plants (Tagetes minuta L. and Lavandula coronopifolia L.) harvested from the Day region (in the north of Djibouti) is the subject of this study. The extraction of essential oils was carried out by hydrodistillation, and the average yield was obtained at a rate of approximately 0.25% for Tagetes minuta L. and 0.42% for Lavandula coronopifolia L. The analyses of these essential oils by gas chromatography coupled with mass spectrometry identified 13 compounds in the essential oil of Tagetes minuta L., including dihydrotagetone (20.8%), artemisia (17.9%), (Z)-tagetenone (12.4%), (-)-spathulenol (11.0%) and estragole (9.5%), were obtained as majority compounds, with a percentage of 71.6%. The essential oil of Lavandula coronopifolia L. is characterized by the presence of 42 compounds, including cis-caryophyllene (18.9%), dehydronerolidol (12.8%), isolongifolanone (11.2%), caryophyllene oxide (8.2%), 10-epi-β-eudesmol (7.7%) and humulene (5.1%), were obtained as the majority chemical constituents, with a percentage of 63.9%. The antimicrobial activities of the essential oils at concentrations of 5% were measured against 12 bacterial strains (Gram positive: Staphylococcus aureus (ATCC 29213), Enterococcus faecalis (ATCC 29212), Streptococcus agalactiae (ATCC 27956), Staphylococcus epidermidis and Corynebacterium sp.; Gram Negative: Pseudomonas aeruginosa (ATCC 27853), Escherichia coli (ATCC 25922), Klebsiella pneumoniae (ATCC 700603), Acinetobacter baumannii (ATCC 19606), Shigella sonnei (ATCC 9290), Salmonella enterica sv. Typhimurium (ATCC 13311) and Enterobacter cloacae), and the results of in vitro experiments showed inhibitory effects against most strains tested except Staphylococcus aureus, Enterococcus faecalis and Streptococcus agalactiae. Additionally, both oils were tested for their ability to selectively kill 13 human cancer cells (K562, A549, HCT116, PC3, U87-MG, MIA-Paca2, HEK293, NCI-N87, RT4, U2OS, A2780, MRC-5 and JIMT-T1), and the results obtained, according to the values of IC₅₀, show the significant activity of two essential oils, particularly on the HCT116 and A2780 lines, which present values between 0.25 µg/mL and 0.45 µg/mL, respectively.

Ocimum plants are of great interest to traditional medicine in the history of several civilizations, particularly in terms of chronic human diseases. Essential oils obtained from this genus have also been used as therapeutic agents. In this present work, two plants of the Ocimum species from Djibouti, Ocimum basilicum L. and Ocimum americanum L., were subjected to hydrodistillation to obtain their essential oils. Gas chromatography-mass spectrometry was performed to determine the chemical composition of both essential oils. Linalool (41.2%) and estragole (30.1%) are the major compounds among the 37 compounds that have been identified in the essential oil of Ocimum basilicum L. (EOOB), and carvotanacetol (38.4%) and estragole (27.5%) are the main compounds among the 42 compounds that have been identified in the essential oil of Ocimum americanum L. (EOOA). Morever, the cytotoxic activity of EOs was evaluated against 13 human cancer cell lines (K562, A549, HCT116, PC3, U87-MG, MIA-Paca2, HEK293, NCI-N87, RT4, U2OS, A2780, MRC -5 and JIMT-T1) using a luminescence spectrophotometric method; hence, the oils showed significant cytotoxic activities. The antibacterial activities of the oils were assayed on five Gram-positive bacteria (Staphylococcus aureus, Enterococcus faecalis, Streptococcus agalactiae, Staphylococcus epidermidis and Corynebacterium sp.) and seven Gram-negative bacteria (Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae, Acinetobacter baumannii, Shigella sonnei, Salmonella enterica sv. Typhimurium and Enterobacter cloacae) by agar disc diffusion methods. Both essential oils exhibited moderate activities against Streptococcus agalactiae, and thus each has an activity against Pseudomonas aeruginosa for EOOB and against Enterobacter cloacae for EOOA, while the others are negative. The findings of this work showed the promising anticancer effects of both oils against total cell lines with a potential for use as natural alternatives to synthetic drugs; however, there was only an antibacterial effect against Streptococcus agalactiae.

The aim of this research was to evaluate the essential oils of two medicinal plants from Djibouti: Cymbopogon schoenanthus (L.) Spreng. and Nepeta azurea R.Br. ex Benth. in cytotoxic activity against thirteen (13) cancer cell lines (A2780, A549, HCT116, HEK-293, JIMT-T1, K562, MIA-Paca2, MRC5, NCI-N87, PC3, RT4, U2OS and U87-MG) and antibacterial activity against seven (7) Gram (−) strains (Acinetobacter baumannii, Enterobacter cloacae, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Salmonella enterica sv. Typhimurium and Shigella sonnei) and five (5) Gram (+) strains (Corynebacterium sp., Enterococcus faecalis, Staphylococcus aureus, Staphylococcus epidermidis and Streptococcus agalactiae). The plants were extracted by hydrodistillation and were analyzed by GC-MS. The main components of Cymbopogon schoenanthus essential oil (CSEO) were 3-isopropenyl-5-methyl-1-cyclohexene (32.3%) and D-Limonene (11.3%), and the main component of Nepeta azurea essential oil (NAEO) was methyl (2E)-2-nonenoate (53.2%). The two essential oils showed inhibitory cytotoxicity activities of all the cancer cells tested; on the other hand, the antibacterial activities are only well-noticed for the CSEO oil at a concentration of 5% against Klebsiella pneumoniae, Pseudomonas aeruginosa, Corynebacterium sp., Enterococcus faecalis and Staphylococcus aureus. Our results demonstrated that the two essential oils could be effective natural anticancer agents, in addition to an antibacterial character for Cymbopogon schoenanthus essential oil.

The current study aimed to investigate the chemical composition, antioxidant, antibacterial, and cytotoxic properties of three extracts (hexane, dichloromethane, and methanol) from Cynoglossum tubiflorus. The composition of the methanolic extract was elucidated using HPLC-HESI-MS/MS analysis. The antioxidant effect was examined using NO, DPPH, FRAP, and TAC assays. Antimicrobial activity was evaluated by broth microdilution using various bacterial strains such as S. aureus, S. epidermidis, P. aeruginosa, E. coli, and K. pneumoniae. Structural disruptions in Gram-positive bacteria were visualized using scanning electron microscopy (SEM). Cytotoxic effects were evaluated on human MRC-5 in culture according to the MTT assay. The outcomes suggest that methanol extract contained a high amount of phenolic compounds (254.35 ± 0.360 mg GAE/g DE and 211.59 ± 0.939 mg QE/g DE). By applying the HPLC-HESI-MS/MS analysis, 32 compounds were identified, including phenolic acids, flavonoids, lignans, and fatty acids. This extract showed strong antioxidant (IC₅₀ = 0.043 ± 0.001 mg/mL) and antimicrobial (MIC = 156 µg/mL) activities. The SEM suggests that cells exhibited membrane distortions characterized by surface depressions and alterations in bacterial shape, including dents, when compared to untreated cells. The in vitro cytotoxicity effect on human MRC-5 cells showed no toxicity effects at a concentration of 600 µg/mL. In silico analysis predicted low toxicity for all tested compounds across four different administration routes. This research indicates that this plant could be explored as a powerful source of natural drugs to target pathogens, with applications in the food, pharmaceutical, and medical industries.