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Feijoa sellowiana leaves and fruits have been investigated as a source of diverse bioactive metabolites. Extract and eight metabolites isolated from F. sellowiana leaves were evaluated for their enzymatic inhibitory activity against a-glucosidase, amylase, tyrosinase, acetylcholinestrerase and butyrylcholinesterase both in vitro and in silico. Feijoa leaves' extract showed strong antioxidant activity and variable levels of inhibitions against target enzymes with a strong anti-tyrosinase activity (115.85 mg Kojic acid equivalent/g). Additionally, a-tocopherol emerged as a potent inhibitor of AChE and BChE (5.40 & 10.38 mmol galantamine equivalent/g, respectively). Which was further investigated through molecular docking and found to develop key enzymatic interactions in AChE and BChE active sites. Also, primetin showed good anti BChE (11.70 mmol galantamine equivalent/g) and anti-tyrosinase inhibition (90.06 mmol Kojic acid equivalent/g) which was also investigated by molecular docking studies. HIGHLIGHTS Isolation of eight bioactive constituents from Feijoa sellowiana leaves. In vitro assays using different enzymatic drug targets were investigated. In silico study was performed to define compound interactions with target proteins. Feijoa leaf is an excellent source of anti-AChE and antityrosinase bioactives.

Hibiscus schizopetalus (Dyer) Hook.f. (Malvaceae) is an ornamental plant. The aim was to investigate its antimicrobial and antioxidant activities. In vitro antiviral, antibacterial, and antioxidant activities of the 70% ethanolic extract (Et-E) of the aerial parts of the plant were determined. The Dichloromethane Fraction (DCM-F) and the n-Butanol Fraction (Bu-F) were assessed using Liquid chromatography–mass spectrometry (LC-MS). The DCM-F showed higher antiviral activities against Coxsackie B4 (CoxB4) viruses (IC50 = 64.13 µg/mL) and adenoviruses (IC50 = 54.88 µg/mL) than acyclovir (IC50 = 72.79 µg/mL for CoxB4 viruses; IC50 = 91.92 µg/mL for adenoviruses). The DCM-F showed higher anti-helicobacter pylori activity (MIC = 3.9 µg/mL) than clarithromycin (MIC = 1.95 µg/mL). The DCM-F inhibited Herpes Simplex Virus (HSV) Type I (IC50 = 29.85 µg/mL) and HSV Type II (IC50 = 74.17 µg/mL). The Bu-F showed higher anti-mycobacterial activity (MIC = 7.81 µg/mL) than isoniazid (MIC = 0.24 µg/mL) and higher antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA)(MIC = 7.81 µg/mL) than vancomycin (MIC = 3.9 µg/mL). Antioxidant assays included total antioxidant capacity (TAC), 2,2′-azino-bis-3-ethylbenzthiazoline-6-sulphonic acid (ABTS), 2,2-diphenyl-1-picryl-hydrazyl (DPPH), and iron reducing power. The Bu-F showed the highest antioxidant activity. Chemical profiles were analyzed using HPLC-HR–ESI–MS to identify the metabolites responsible for these biological activities. We identified more than 60 metabolites that belong to anthocyanins, flavonoids, phenolics, terpenes, sterols, and fatty acids. In conclusion, Hibiscusschizopetalus is endowed with metabolites that could be used against viruses and antibiotic-resistant bacteria. They can also be potent antioxidants.

(1) Background: Bacterial resistance to antibiotics is a global life-threatening issue. Antivirulence therapy is a promising approach to combat bacterial infections as it disarms the bacteria from their virulence factors with reduced selective pressure and a lower chance of resistance. (2) Methods: Callistemon citrinus leaf extract and its major constituent, Pulverulentone A, were tested for their ability to inhibit biofilm, exopolysaccharides, pyocyanin and proteases produced by MDR P. aeruginosa. In addition, a Galleria mellonella larvae model was employed to evaluate the in vivo cytotoxicity of Pulverulentone A and its ability to combat Pseudomonas infection. Docking study was further performed to investigate Pulverulentone A druggability against main quorum sensing (QS) targets expressed by P. aeruginosa; (3) Results: Both C. citrinus extract and the isolated compound could inhibit biofilm formation, extracellular polymeric substances (EPS) and pigment production by the tested isolates. Unexpectedly, no significant inhibition was observed on proteases production. The in silico docking analysis revealed good interactions of Pulverulentone A with all QS targets examined (LasR, MyfR/PqsR, QscR). Pulverulentone A was safe up to 400 µg·mL−1 in Galleria caterpillars. Moreover, pre-treatment of P. aeruginosa with Pulverulentone A slightly enhanced the survival of the infected larvae. (4) Conclusions: The present study proves Pulverulentone A safety with significant in vitro and in silico antivirulence potential against P. aeruginosa.

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